From 742526451180db627865598fc4f1c1a1aa4a43f8 Mon Sep 17 00:00:00 2001
From: Pouya Yarandi <pouya.yarandi@divar.ir>
Date: Thu, 18 Apr 2024 23:37:02 +0330
Subject: [PATCH 1/4] Add test for failing scenario

---
 Tests/SwiftProtobufTests/TestHelpers.swift    | 258 ++++++++++++++++++
 .../Test_OneodFields_Decoding.swift           |  72 +++++
 2 files changed, 330 insertions(+)
 create mode 100644 Tests/SwiftProtobufTests/Test_OneodFields_Decoding.swift

diff --git a/Tests/SwiftProtobufTests/TestHelpers.swift b/Tests/SwiftProtobufTests/TestHelpers.swift
index 4eedd1027..5b17fec05 100644
--- a/Tests/SwiftProtobufTests/TestHelpers.swift
+++ b/Tests/SwiftProtobufTests/TestHelpers.swift
@@ -469,3 +469,261 @@ extension PBTestVisitor {
     XCTFail("Unexpected map<*, Message>: \(fieldNumber) = \(value)")
   }
 }
+
+struct PBTestDecoder: Decoder {
+
+  enum DecodingMode {
+    case get
+    case set(Any)
+  }
+
+  var fieldNumber: Int?
+  var decodingMode: DecodingMode = .get
+  private(set) var value: Any
+
+  init(fieldNumber: Int, decodingMode: DecodingMode = .get) {
+    self.fieldNumber = fieldNumber
+    self.decodingMode = decodingMode
+    self.value = Void()
+  }
+
+  mutating func handleConflictingOneOf() throws {}
+
+  mutating func nextFieldNumber() throws -> Int? {
+    defer { fieldNumber = nil }
+    return fieldNumber
+  }
+
+  private mutating func decode<T>(_ value: inout T) {
+    switch decodingMode {
+    case .get:
+      self.value = value
+    case .set(let v):
+      guard let v = v as? T else { return }
+      value = v
+    }
+  }
+
+  mutating func decodeSingularFloatField(value: inout Float) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularFloatField(value: inout Float?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedFloatField(value: inout [Float]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularDoubleField(value: inout Double) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularDoubleField(value: inout Double?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedDoubleField(value: inout [Double]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularInt32Field(value: inout Int32) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularInt32Field(value: inout Int32?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedInt32Field(value: inout [Int32]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularInt64Field(value: inout Int64) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularInt64Field(value: inout Int64?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedInt64Field(value: inout [Int64]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularUInt32Field(value: inout UInt32) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularUInt32Field(value: inout UInt32?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedUInt32Field(value: inout [UInt32]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularUInt64Field(value: inout UInt64) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularUInt64Field(value: inout UInt64?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedUInt64Field(value: inout [UInt64]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularSInt32Field(value: inout Int32) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularSInt32Field(value: inout Int32?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedSInt32Field(value: inout [Int32]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularSInt64Field(value: inout Int64) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularSInt64Field(value: inout Int64?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedSInt64Field(value: inout [Int64]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularFixed32Field(value: inout UInt32) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularFixed32Field(value: inout UInt32?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedFixed32Field(value: inout [UInt32]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularFixed64Field(value: inout UInt64) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularFixed64Field(value: inout UInt64?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedFixed64Field(value: inout [UInt64]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularSFixed32Field(value: inout Int32) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularSFixed32Field(value: inout Int32?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedSFixed32Field(value: inout [Int32]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularSFixed64Field(value: inout Int64) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularSFixed64Field(value: inout Int64?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedSFixed64Field(value: inout [Int64]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularBoolField(value: inout Bool) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularBoolField(value: inout Bool?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedBoolField(value: inout [Bool]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularStringField(value: inout String) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularStringField(value: inout String?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedStringField(value: inout [String]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularBytesField(value: inout Data) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularBytesField(value: inout Data?) throws {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedBytesField(value: inout [Data]) throws {
+    decode(&value)
+  }
+
+  mutating func decodeSingularEnumField<E>(value: inout E) throws where E : SwiftProtobuf.Enum, E.RawValue == Int {
+    decode(&value)
+  }
+
+  mutating func decodeSingularEnumField<E>(value: inout E?) throws where E : SwiftProtobuf.Enum, E.RawValue == Int {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedEnumField<E>(value: inout [E]) throws where E : SwiftProtobuf.Enum, E.RawValue == Int {
+    decode(&value)
+  }
+
+  mutating func decodeSingularMessageField<M>(value: inout M?) throws where M : SwiftProtobuf.Message {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedMessageField<M>(value: inout [M]) throws where M : SwiftProtobuf.Message {
+    decode(&value)
+  }
+
+  mutating func decodeSingularGroupField<G>(value: inout G?) throws where G : SwiftProtobuf.Message {
+    decode(&value)
+  }
+
+  mutating func decodeRepeatedGroupField<G>(value: inout [G]) throws where G : SwiftProtobuf.Message {
+    decode(&value)
+  }
+
+  mutating func decodeMapField<KeyType, ValueType>(fieldType: SwiftProtobuf._ProtobufMap<KeyType, ValueType>.Type, value: inout SwiftProtobuf._ProtobufMap<KeyType, ValueType>.BaseType) throws where KeyType : SwiftProtobuf.MapKeyType, ValueType : SwiftProtobuf.MapValueType {
+    decode(&value)
+  }
+
+  mutating func decodeMapField<KeyType, ValueType>(fieldType: SwiftProtobuf._ProtobufEnumMap<KeyType, ValueType>.Type, value: inout SwiftProtobuf._ProtobufEnumMap<KeyType, ValueType>.BaseType) throws where KeyType : SwiftProtobuf.MapKeyType, ValueType : SwiftProtobuf.Enum, ValueType.RawValue == Int {
+    decode(&value)
+  }
+
+  mutating func decodeMapField<KeyType, ValueType>(fieldType: SwiftProtobuf._ProtobufMessageMap<KeyType, ValueType>.Type, value: inout SwiftProtobuf._ProtobufMessageMap<KeyType, ValueType>.BaseType) throws where KeyType : SwiftProtobuf.MapKeyType, ValueType : Hashable, ValueType : SwiftProtobuf.Message {
+    decode(&value)
+  }
+
+  mutating func decodeExtensionField(values: inout SwiftProtobuf.ExtensionFieldValueSet, messageType: any SwiftProtobuf.Message.Type, fieldNumber: Int) throws {}
+
+}
diff --git a/Tests/SwiftProtobufTests/Test_OneodFields_Decoding.swift b/Tests/SwiftProtobufTests/Test_OneodFields_Decoding.swift
new file mode 100644
index 000000000..2b500b42c
--- /dev/null
+++ b/Tests/SwiftProtobufTests/Test_OneodFields_Decoding.swift
@@ -0,0 +1,72 @@
+// Test/Sources/TestSuite/Test_OneofFields_Decoding.swift
+//
+// Copyright (c) 2014 - 2024 Apple Inc. and the project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See LICENSE.txt for license information:
+// https://github.com/apple/swift-protobuf/blob/main/LICENSE.txt
+//
+// -----------------------------------------------------------------------------
+///
+/// Exercises the dedcode for primitive fields within a oneof.
+///
+// -----------------------------------------------------------------------------
+
+import Foundation
+import XCTest
+import SwiftProtobuf
+
+final class Test_OneofFields_Decoding: XCTestCase {
+  func testDecodeOneofCaptureField() throws {
+    var message = SwiftProtoTesting_Fuzz_Message()
+
+    message.oneofInt32 = 1
+    var d1 = PBTestDecoder(fieldNumber: 61)
+    try message.decodeMessage(decoder: &d1)
+    XCTAssertEqual(d1.value as? Int32, Int32(1))
+
+    message.oneofInt64 = 1
+    var d2 = PBTestDecoder(fieldNumber: 62)
+    try message.decodeMessage(decoder: &d2)
+    XCTAssertEqual(d2.value as? Int64, Int64(1))
+
+    message.oneofString = "message"
+    var d3 = PBTestDecoder(fieldNumber: 74)
+    try message.decodeMessage(decoder: &d3)
+    XCTAssertEqual(d3.value as? String, "message")
+
+    message.oneofBytes = "message".data(using: .utf8)!
+    var d4 = PBTestDecoder(fieldNumber: 75)
+    try message.decodeMessage(decoder: &d4)
+    XCTAssertEqual(d4.value as? Data, "message".data(using: .utf8)!)
+
+    message.oneofEnum = .two
+    var d5 = PBTestDecoder(fieldNumber: 76)
+    try message.decodeMessage(decoder: &d5)
+    XCTAssertEqual(d5.value as? SwiftProtoTesting_Fuzz_AnEnum, .two)
+  }
+
+  func testDecodeOneofModifyField() throws {
+    var message = SwiftProtoTesting_Fuzz_Message()
+
+    var d1 = PBTestDecoder(fieldNumber: 61, decodingMode: .set(Int32(2)))
+    try message.decodeMessage(decoder: &d1)
+    XCTAssertEqual(message.oneofInt32, Int32(2))
+
+    var d2 = PBTestDecoder(fieldNumber: 62, decodingMode: .set(Int64(2)))
+    try message.decodeMessage(decoder: &d2)
+    XCTAssertEqual(message.oneofInt64, Int64(2))
+
+    var d3 = PBTestDecoder(fieldNumber: 74, decodingMode: .set("message"))
+    try message.decodeMessage(decoder: &d3)
+    XCTAssertEqual(message.oneofString, "message")
+
+    var d4 = PBTestDecoder(fieldNumber: 75, decodingMode: .set("message".data(using: .utf8)!))
+    try message.decodeMessage(decoder: &d4)
+    XCTAssertEqual(message.oneofBytes, "message".data(using: .utf8)!)
+
+    var d5 = PBTestDecoder(fieldNumber: 76, decodingMode: .set(SwiftProtoTesting_Fuzz_AnEnum.two))
+    try message.decodeMessage(decoder: &d5)
+    XCTAssertEqual(message.oneofEnum, .two)
+  }
+}

From 1a58f91e7842c725807384331751b83f8fd4b1cd Mon Sep 17 00:00:00 2001
From: Pouya Yarandi <pouya.yarandi@divar.ir>
Date: Thu, 18 Apr 2024 23:55:04 +0330
Subject: [PATCH 2/4] Regenerate proto messages

---
 .../Sources/FuzzCommon/fuzz_testing.pb.swift  | 16 +++++++++++
 .../conformance/conformance.pb.swift          | 13 +++++++++
 .../protobuf/test_messages_proto2.pb.swift    |  8 ++++++
 .../protobuf/test_messages_proto3.pb.swift    |  9 ++++++
 .../google/protobuf/struct.pb.swift           |  4 +++
 .../pluginlib_descriptor_test.pb.swift        |  5 ++++
 .../pluginlib_descriptor_test2.pb.swift       |  3 ++
 .../SwiftProtobufTests/fuzz_testing.pb.swift  | 16 +++++++++++
 .../test_messages_proto3.pb.swift             |  9 ++++++
 .../SwiftProtobufTests/unittest.pb.swift      |  7 +++++
 .../unittest_preserve_unknown_enum.pb.swift   |  4 +++
 .../unittest_preserve_unknown_enum2.pb.swift  |  2 ++
 .../unittest_proto3.pb.swift                  |  3 ++
 ...unittest_swift_all_required_types.pb.swift |  3 ++
 .../unittest_swift_fieldorder.pb.swift        | 12 ++++++++
 .../unittest_swift_naming.pb.swift            |  4 +++
 ...unittest_swift_oneof_all_required.pb.swift |  1 +
 .../unittest_swift_oneof_merging.pb.swift     |  3 ++
 .../unittest_swift_runtime_proto2.pb.swift    | 16 +++++++++++
 .../unittest_swift_runtime_proto3.pb.swift    | 16 +++++++++++
 .../upstream/conformance/conformance.pb.swift | 13 +++++++++
 .../upstream/google/protobuf/struct.pb.swift  |  4 +++
 .../protobuf/test_messages_proto2.pb.swift    |  8 ++++++
 .../protobuf/test_messages_proto3.pb.swift    |  9 ++++++
 .../google/protobuf/unittest.pb.swift         | 28 +++++++++++++++++++
 .../protobuf/unittest_custom_options.pb.swift |  1 +
 .../google/protobuf/unittest_lite.pb.swift    | 14 ++++++++++
 .../unittest_no_field_presence.pb.swift       |  3 ++
 .../protobuf/unittest_optimize_for.pb.swift   |  2 ++
 .../unittest_preserve_unknown_enum.pb.swift   |  4 +++
 .../unittest_preserve_unknown_enum2.pb.swift  |  2 ++
 .../google/protobuf/unittest_proto3.pb.swift  |  4 +++
 .../protobuf/unittest_proto3_arena.pb.swift   |  3 ++
 .../unittest_proto3_arena_lite.pb.swift       |  3 ++
 .../protobuf/unittest_proto3_lite.pb.swift    |  3 ++
 .../protobuf/unittest_retention.pb.swift      |  1 +
 Sources/Conformance/conformance.pb.swift      | 13 +++++++++
 .../Conformance/test_messages_proto2.pb.swift |  8 ++++++
 .../Conformance/test_messages_proto3.pb.swift |  9 ++++++
 Sources/SwiftProtobuf/struct.pb.swift         |  4 +++
 Sources/protoc-gen-swift/OneofGenerator.swift |  1 +
 .../SwiftProtobufTests/fuzz_testing.pb.swift  | 16 +++++++++++
 .../test_messages_proto3.pb.swift             |  9 ++++++
 Tests/SwiftProtobufTests/unittest.pb.swift    |  7 +++++
 .../unittest_preserve_unknown_enum.pb.swift   |  4 +++
 .../unittest_preserve_unknown_enum2.pb.swift  |  2 ++
 .../unittest_proto3.pb.swift                  |  3 ++
 ...unittest_swift_all_required_types.pb.swift |  3 ++
 .../unittest_swift_fieldorder.pb.swift        | 12 ++++++++
 .../unittest_swift_naming.pb.swift            |  4 +++
 ...unittest_swift_oneof_all_required.pb.swift |  1 +
 .../unittest_swift_oneof_merging.pb.swift     |  3 ++
 .../unittest_swift_runtime_proto2.pb.swift    | 16 +++++++++++
 .../unittest_swift_runtime_proto3.pb.swift    | 16 +++++++++++
 54 files changed, 387 insertions(+)

diff --git a/FuzzTesting/Sources/FuzzCommon/fuzz_testing.pb.swift b/FuzzTesting/Sources/FuzzCommon/fuzz_testing.pb.swift
index 241215849..eee2ecb1f 100644
--- a/FuzzTesting/Sources/FuzzCommon/fuzz_testing.pb.swift
+++ b/FuzzTesting/Sources/FuzzCommon/fuzz_testing.pb.swift
@@ -3471,6 +3471,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         case 49: try { try decoder.decodeRepeatedMessageField(value: &_storage._repeatedMessage) }()
         case 61: try {
           var v: Int32?
+          if case .oneofInt32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3479,6 +3480,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 62: try {
           var v: Int64?
+          if case .oneofInt64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3487,6 +3489,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 63: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3495,6 +3498,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 64: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3503,6 +3507,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 65: try {
           var v: Int32?
+          if case .oneofSint32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3511,6 +3516,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 66: try {
           var v: Int64?
+          if case .oneofSint64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3519,6 +3525,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 67: try {
           var v: UInt32?
+          if case .oneofFixed32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFixed32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3527,6 +3534,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 68: try {
           var v: UInt64?
+          if case .oneofFixed64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFixed64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3535,6 +3543,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 69: try {
           var v: Int32?
+          if case .oneofSfixed32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSFixed32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3543,6 +3552,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 70: try {
           var v: Int64?
+          if case .oneofSfixed64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSFixed64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3551,6 +3561,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 71: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3559,6 +3570,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 72: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3567,6 +3579,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 73: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3575,6 +3588,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 74: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3583,6 +3597,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 75: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3591,6 +3606,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 76: try {
           var v: SwiftProtoTesting_Fuzz_AnEnum?
+          if case .oneofEnum(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/Conformance/conformance/conformance.pb.swift b/Reference/Conformance/conformance/conformance.pb.swift
index ef099db7b..cea6cf759 100644
--- a/Reference/Conformance/conformance/conformance.pb.swift
+++ b/Reference/Conformance/conformance/conformance.pb.swift
@@ -491,6 +491,7 @@ extension Conformance_ConformanceRequest: SwiftProtobuf.Message, SwiftProtobuf._
       switch fieldNumber {
       case 1: try {
         var v: Data?
+        if case .protobufPayload(let _v) = self.payload {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.payload != nil {try decoder.handleConflictingOneOf()}
@@ -499,6 +500,7 @@ extension Conformance_ConformanceRequest: SwiftProtobuf.Message, SwiftProtobuf._
       }()
       case 2: try {
         var v: String?
+        if case .jsonPayload(let _v) = self.payload {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.payload != nil {try decoder.handleConflictingOneOf()}
@@ -511,6 +513,7 @@ extension Conformance_ConformanceRequest: SwiftProtobuf.Message, SwiftProtobuf._
       case 6: try { try decoder.decodeSingularMessageField(value: &self._jspbEncodingOptions) }()
       case 7: try {
         var v: String?
+        if case .jspbPayload(let _v) = self.payload {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.payload != nil {try decoder.handleConflictingOneOf()}
@@ -519,6 +522,7 @@ extension Conformance_ConformanceRequest: SwiftProtobuf.Message, SwiftProtobuf._
       }()
       case 8: try {
         var v: String?
+        if case .textPayload(let _v) = self.payload {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.payload != nil {try decoder.handleConflictingOneOf()}
@@ -610,6 +614,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       switch fieldNumber {
       case 1: try {
         var v: String?
+        if case .parseError(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -618,6 +623,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 2: try {
         var v: String?
+        if case .runtimeError(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -626,6 +632,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 3: try {
         var v: Data?
+        if case .protobufPayload(let _v) = self.result {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -634,6 +641,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 4: try {
         var v: String?
+        if case .jsonPayload(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -642,6 +650,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 5: try {
         var v: String?
+        if case .skipped(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -650,6 +659,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 6: try {
         var v: String?
+        if case .serializeError(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -658,6 +668,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 7: try {
         var v: String?
+        if case .jspbPayload(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -666,6 +677,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 8: try {
         var v: String?
+        if case .textPayload(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -674,6 +686,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 9: try {
         var v: String?
+        if case .timeoutError(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/Conformance/google/protobuf/test_messages_proto2.pb.swift b/Reference/Conformance/google/protobuf/test_messages_proto2.pb.swift
index 08e6faeb1..5ae2c7845 100644
--- a/Reference/Conformance/google/protobuf/test_messages_proto2.pb.swift
+++ b/Reference/Conformance/google/protobuf/test_messages_proto2.pb.swift
@@ -2616,6 +2616,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         case 102: try { try decoder.decodeRepeatedEnumField(value: &_storage._unpackedNestedEnum) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2637,6 +2638,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2645,6 +2647,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2653,6 +2656,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 115: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2661,6 +2665,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 116: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2669,6 +2674,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 117: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2677,6 +2683,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 118: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2685,6 +2692,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 119: try {
           var v: ProtobufTestMessages_Proto2_TestAllTypesProto2.NestedEnum?
+          if case .oneofEnum(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/Conformance/google/protobuf/test_messages_proto3.pb.swift b/Reference/Conformance/google/protobuf/test_messages_proto3.pb.swift
index 367b0dc91..87afba6bf 100644
--- a/Reference/Conformance/google/protobuf/test_messages_proto3.pb.swift
+++ b/Reference/Conformance/google/protobuf/test_messages_proto3.pb.swift
@@ -1743,6 +1743,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         case 102: try { try decoder.decodeRepeatedEnumField(value: &_storage._unpackedNestedEnum) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1764,6 +1765,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1772,6 +1774,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1780,6 +1783,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 115: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1788,6 +1792,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 116: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1796,6 +1801,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 117: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1804,6 +1810,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 118: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1812,6 +1819,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 119: try {
           var v: ProtobufTestMessages_Proto3_TestAllTypesProto3.NestedEnum?
+          if case .oneofEnum(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1820,6 +1828,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 120: try {
           var v: SwiftProtobuf.Google_Protobuf_NullValue?
+          if case .oneofNullValue(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobuf/google/protobuf/struct.pb.swift b/Reference/SwiftProtobuf/google/protobuf/struct.pb.swift
index fd0afcc0c..ece59f97f 100644
--- a/Reference/SwiftProtobuf/google/protobuf/struct.pb.swift
+++ b/Reference/SwiftProtobuf/google/protobuf/struct.pb.swift
@@ -273,6 +273,7 @@ extension Google_Protobuf_Value: Message, _MessageImplementationBase, _ProtoName
       switch fieldNumber {
       case 1: try {
         var v: Google_Protobuf_NullValue?
+        if case .nullValue(let _v) = self.kind {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.kind != nil {try decoder.handleConflictingOneOf()}
@@ -281,6 +282,7 @@ extension Google_Protobuf_Value: Message, _MessageImplementationBase, _ProtoName
       }()
       case 2: try {
         var v: Double?
+        if case .numberValue(let _v) = self.kind {v = _v}
         try decoder.decodeSingularDoubleField(value: &v)
         if let v = v {
           if self.kind != nil {try decoder.handleConflictingOneOf()}
@@ -289,6 +291,7 @@ extension Google_Protobuf_Value: Message, _MessageImplementationBase, _ProtoName
       }()
       case 3: try {
         var v: String?
+        if case .stringValue(let _v) = self.kind {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.kind != nil {try decoder.handleConflictingOneOf()}
@@ -297,6 +300,7 @@ extension Google_Protobuf_Value: Message, _MessageImplementationBase, _ProtoName
       }()
       case 4: try {
         var v: Bool?
+        if case .boolValue(let _v) = self.kind {v = _v}
         try decoder.decodeSingularBoolField(value: &v)
         if let v = v {
           if self.kind != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufPluginLibraryTests/pluginlib_descriptor_test.pb.swift b/Reference/SwiftProtobufPluginLibraryTests/pluginlib_descriptor_test.pb.swift
index 118cea5ed..df372e71a 100644
--- a/Reference/SwiftProtobufPluginLibraryTests/pluginlib_descriptor_test.pb.swift
+++ b/Reference/SwiftProtobufPluginLibraryTests/pluginlib_descriptor_test.pb.swift
@@ -574,6 +574,7 @@ extension SDTTopLevelMessage: SwiftProtobuf.Message, SwiftProtobuf._MessageImple
         case 2: try { try decoder.decodeSingularInt32Field(value: &_storage._field2) }()
         case 3: try {
           var v: SDTTopLevelEnum?
+          if case .field3(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -582,6 +583,7 @@ extension SDTTopLevelMessage: SwiftProtobuf.Message, SwiftProtobuf._MessageImple
         }()
         case 4: try {
           var v: SDTTopLevelMessage.SubEnum?
+          if case .field4(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -955,6 +957,7 @@ extension SDTProto2MessageForPresence: SwiftProtobuf.Message, SwiftProtobuf._Mes
       case 24: try { try decoder.decodeRepeatedMessageField(value: &self.repeatMessageField) }()
       case 31: try {
         var v: String?
+        if case .oneofStrField(let _v) = self.o {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -963,6 +966,7 @@ extension SDTProto2MessageForPresence: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 32: try {
         var v: Int32?
+        if case .oneofInt32Field(let _v) = self.o {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -971,6 +975,7 @@ extension SDTProto2MessageForPresence: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 33: try {
         var v: SDTTopLevelEnum?
+        if case .oneofEnumField(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufPluginLibraryTests/pluginlib_descriptor_test2.pb.swift b/Reference/SwiftProtobufPluginLibraryTests/pluginlib_descriptor_test2.pb.swift
index ad60f1671..d93d44b75 100644
--- a/Reference/SwiftProtobufPluginLibraryTests/pluginlib_descriptor_test2.pb.swift
+++ b/Reference/SwiftProtobufPluginLibraryTests/pluginlib_descriptor_test2.pb.swift
@@ -248,6 +248,7 @@ extension SwiftDescriptorTest_Proto3MessageForPresence: SwiftProtobuf.Message, S
       case 24: try { try decoder.decodeRepeatedMessageField(value: &self.repeatMessageField) }()
       case 31: try {
         var v: String?
+        if case .oneofStrField(let _v) = self.o {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -256,6 +257,7 @@ extension SwiftDescriptorTest_Proto3MessageForPresence: SwiftProtobuf.Message, S
       }()
       case 32: try {
         var v: Int32?
+        if case .oneofInt32Field(let _v) = self.o {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -264,6 +266,7 @@ extension SwiftDescriptorTest_Proto3MessageForPresence: SwiftProtobuf.Message, S
       }()
       case 33: try {
         var v: SwiftDescriptorTest_Proto3MessageForPresence.SubEnum?
+        if case .oneofEnumField(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufTests/fuzz_testing.pb.swift b/Reference/SwiftProtobufTests/fuzz_testing.pb.swift
index c4989d82f..6cca011c4 100644
--- a/Reference/SwiftProtobufTests/fuzz_testing.pb.swift
+++ b/Reference/SwiftProtobufTests/fuzz_testing.pb.swift
@@ -3471,6 +3471,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         case 49: try { try decoder.decodeRepeatedMessageField(value: &_storage._repeatedMessage) }()
         case 61: try {
           var v: Int32?
+          if case .oneofInt32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3479,6 +3480,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 62: try {
           var v: Int64?
+          if case .oneofInt64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3487,6 +3489,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 63: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3495,6 +3498,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 64: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3503,6 +3507,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 65: try {
           var v: Int32?
+          if case .oneofSint32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3511,6 +3516,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 66: try {
           var v: Int64?
+          if case .oneofSint64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3519,6 +3525,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 67: try {
           var v: UInt32?
+          if case .oneofFixed32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFixed32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3527,6 +3534,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 68: try {
           var v: UInt64?
+          if case .oneofFixed64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFixed64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3535,6 +3543,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 69: try {
           var v: Int32?
+          if case .oneofSfixed32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSFixed32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3543,6 +3552,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 70: try {
           var v: Int64?
+          if case .oneofSfixed64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSFixed64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3551,6 +3561,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 71: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3559,6 +3570,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 72: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3567,6 +3579,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 73: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3575,6 +3588,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 74: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3583,6 +3597,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 75: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3591,6 +3606,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 76: try {
           var v: SwiftProtoTesting_Fuzz_AnEnum?
+          if case .oneofEnum(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufTests/test_messages_proto3.pb.swift b/Reference/SwiftProtobufTests/test_messages_proto3.pb.swift
index 23f15c768..224739838 100644
--- a/Reference/SwiftProtobufTests/test_messages_proto3.pb.swift
+++ b/Reference/SwiftProtobufTests/test_messages_proto3.pb.swift
@@ -1215,6 +1215,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         case 73: try { try decoder.decodeMapField(fieldType: SwiftProtobuf._ProtobufEnumMap<SwiftProtobuf.ProtobufString,SwiftProtoTesting_Test3_TestAllTypesProto3.NestedEnum>.self, value: &_storage._mapStringNestedEnum) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1236,6 +1237,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1244,6 +1246,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1252,6 +1255,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 115: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1260,6 +1264,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 116: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1268,6 +1273,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 117: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1276,6 +1282,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 118: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1284,6 +1291,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 119: try {
           var v: SwiftProtoTesting_Test3_TestAllTypesProto3.NestedEnum?
+          if case .oneofEnum(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1292,6 +1300,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 120: try {
           var v: SwiftProtobuf.Google_Protobuf_NullValue?
+          if case .oneofNullValue(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufTests/unittest.pb.swift b/Reference/SwiftProtobufTests/unittest.pb.swift
index 28c5d01de..aa1abfaf3 100644
--- a/Reference/SwiftProtobufTests/unittest.pb.swift
+++ b/Reference/SwiftProtobufTests/unittest.pb.swift
@@ -4298,6 +4298,7 @@ extension SwiftProtoTesting_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf._
         case 85: try { try decoder.decodeSingularStringField(value: &_storage._defaultCord) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -4319,6 +4320,7 @@ extension SwiftProtoTesting_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -4327,6 +4329,7 @@ extension SwiftProtoTesting_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -6043,6 +6046,7 @@ extension SwiftProtoTesting_TestOneof: SwiftProtobuf.Message, SwiftProtobuf._Mes
       switch fieldNumber {
       case 1: try {
         var v: Int32?
+        if case .fooInt(let _v) = self.foo {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -6051,6 +6055,7 @@ extension SwiftProtoTesting_TestOneof: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 2: try {
         var v: String?
+        if case .fooString(let _v) = self.foo {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -6186,6 +6191,7 @@ extension SwiftProtoTesting_TestRequiredOneof: SwiftProtobuf.Message, SwiftProto
       switch fieldNumber {
       case 1: try {
         var v: Int32?
+        if case .fooInt(let _v) = self.foo {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -6194,6 +6200,7 @@ extension SwiftProtoTesting_TestRequiredOneof: SwiftProtobuf.Message, SwiftProto
       }()
       case 2: try {
         var v: String?
+        if case .fooString(let _v) = self.foo {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufTests/unittest_preserve_unknown_enum.pb.swift b/Reference/SwiftProtobufTests/unittest_preserve_unknown_enum.pb.swift
index aac6b31bf..8f2610962 100644
--- a/Reference/SwiftProtobufTests/unittest_preserve_unknown_enum.pb.swift
+++ b/Reference/SwiftProtobufTests/unittest_preserve_unknown_enum.pb.swift
@@ -259,6 +259,7 @@ extension SwiftProtoTesting_UnknownEnum_Proto3_MyMessage: SwiftProtobuf.Message,
       case 4: try { try decoder.decodeRepeatedEnumField(value: &self.repeatedPackedUnexpectedE) }()
       case 5: try {
         var v: SwiftProtoTesting_UnknownEnum_Proto3_MyEnum?
+        if case .oneofE1(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -267,6 +268,7 @@ extension SwiftProtoTesting_UnknownEnum_Proto3_MyMessage: SwiftProtobuf.Message,
       }()
       case 6: try {
         var v: SwiftProtoTesting_UnknownEnum_Proto3_MyEnum?
+        if case .oneofE2(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -343,6 +345,7 @@ extension SwiftProtoTesting_UnknownEnum_Proto3_MyMessagePlusExtra: SwiftProtobuf
       case 4: try { try decoder.decodeRepeatedEnumField(value: &self.repeatedPackedUnexpectedE) }()
       case 5: try {
         var v: SwiftProtoTesting_UnknownEnum_Proto3_MyEnumPlusExtra?
+        if case .oneofE1(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -351,6 +354,7 @@ extension SwiftProtoTesting_UnknownEnum_Proto3_MyMessagePlusExtra: SwiftProtobuf
       }()
       case 6: try {
         var v: SwiftProtoTesting_UnknownEnum_Proto3_MyEnumPlusExtra?
+        if case .oneofE2(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufTests/unittest_preserve_unknown_enum2.pb.swift b/Reference/SwiftProtobufTests/unittest_preserve_unknown_enum2.pb.swift
index 406ca934d..5aed56231 100644
--- a/Reference/SwiftProtobufTests/unittest_preserve_unknown_enum2.pb.swift
+++ b/Reference/SwiftProtobufTests/unittest_preserve_unknown_enum2.pb.swift
@@ -166,6 +166,7 @@ extension SwiftProtoTesting_UnknownEnum_Proto2_MyMessage: SwiftProtobuf.Message,
       case 4: try { try decoder.decodeRepeatedEnumField(value: &self.repeatedPackedUnexpectedE) }()
       case 5: try {
         var v: SwiftProtoTesting_UnknownEnum_Proto2_MyEnum?
+        if case .oneofE1(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -174,6 +175,7 @@ extension SwiftProtoTesting_UnknownEnum_Proto2_MyMessage: SwiftProtobuf.Message,
       }()
       case 6: try {
         var v: SwiftProtoTesting_UnknownEnum_Proto2_MyEnum?
+        if case .oneofE2(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufTests/unittest_proto3.pb.swift b/Reference/SwiftProtobufTests/unittest_proto3.pb.swift
index 87f861d19..9ce663000 100644
--- a/Reference/SwiftProtobufTests/unittest_proto3.pb.swift
+++ b/Reference/SwiftProtobufTests/unittest_proto3.pb.swift
@@ -891,6 +891,7 @@ extension SwiftProtoTesting_Proto3_TestAllTypes: SwiftProtobuf.Message, SwiftPro
         case 57: try { try decoder.decodeRepeatedMessageField(value: &_storage._repeatedLazyMessage) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -912,6 +913,7 @@ extension SwiftProtoTesting_Proto3_TestAllTypes: SwiftProtobuf.Message, SwiftPro
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -920,6 +922,7 @@ extension SwiftProtoTesting_Proto3_TestAllTypes: SwiftProtobuf.Message, SwiftPro
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufTests/unittest_swift_all_required_types.pb.swift b/Reference/SwiftProtobufTests/unittest_swift_all_required_types.pb.swift
index 6638e4d40..cf992c22c 100644
--- a/Reference/SwiftProtobufTests/unittest_swift_all_required_types.pb.swift
+++ b/Reference/SwiftProtobufTests/unittest_swift_all_required_types.pb.swift
@@ -989,6 +989,7 @@ extension SwiftProtoTesting_TestAllRequiredTypes: SwiftProtobuf.Message, SwiftPr
         case 85: try { try decoder.decodeSingularStringField(value: &_storage._defaultCord) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1010,6 +1011,7 @@ extension SwiftProtoTesting_TestAllRequiredTypes: SwiftProtobuf.Message, SwiftPr
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1018,6 +1020,7 @@ extension SwiftProtoTesting_TestAllRequiredTypes: SwiftProtobuf.Message, SwiftPr
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufTests/unittest_swift_fieldorder.pb.swift b/Reference/SwiftProtobufTests/unittest_swift_fieldorder.pb.swift
index ab4754d5f..acfa9cbcd 100644
--- a/Reference/SwiftProtobufTests/unittest_swift_fieldorder.pb.swift
+++ b/Reference/SwiftProtobufTests/unittest_swift_fieldorder.pb.swift
@@ -389,6 +389,7 @@ extension SwiftProtoTesting_Order_TestFieldOrderings: SwiftProtobuf.Message, Swi
       case 1: try { try decoder.decodeSingularInt64Field(value: &self._myInt) }()
       case 9: try {
         var v: Bool?
+        if case .oneofBool(let _v) = self.options {v = _v}
         try decoder.decodeSingularBoolField(value: &v)
         if let v = v {
           if self.options != nil {try decoder.handleConflictingOneOf()}
@@ -397,6 +398,7 @@ extension SwiftProtoTesting_Order_TestFieldOrderings: SwiftProtobuf.Message, Swi
       }()
       case 10: try {
         var v: Int32?
+        if case .oneofInt32(let _v) = self.options {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.options != nil {try decoder.handleConflictingOneOf()}
@@ -406,6 +408,7 @@ extension SwiftProtoTesting_Order_TestFieldOrderings: SwiftProtobuf.Message, Swi
       case 11: try { try decoder.decodeSingularStringField(value: &self._myString) }()
       case 60: try {
         var v: Int64?
+        if case .oneofInt64(let _v) = self.options {v = _v}
         try decoder.decodeSingularInt64Field(value: &v)
         if let v = v {
           if self.options != nil {try decoder.handleConflictingOneOf()}
@@ -415,6 +418,7 @@ extension SwiftProtoTesting_Order_TestFieldOrderings: SwiftProtobuf.Message, Swi
       case 101: try { try decoder.decodeSingularFloatField(value: &self._myFloat) }()
       case 150: try {
         var v: String?
+        if case .oneofString(let _v) = self.options {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.options != nil {try decoder.handleConflictingOneOf()}
@@ -549,6 +553,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       switch fieldNumber {
       case 1: try {
         var v: Int32?
+        if case .a(let _v) = self.oGood {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oGood != nil {try decoder.handleConflictingOneOf()}
@@ -557,6 +562,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       }()
       case 26: try {
         var v: Int32?
+        if case .b(let _v) = self.oGood {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oGood != nil {try decoder.handleConflictingOneOf()}
@@ -565,6 +571,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       }()
       case 101: try {
         var v: Int32?
+        if case .a2(let _v) = self.oConflictField {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oConflictField != nil {try decoder.handleConflictingOneOf()}
@@ -574,6 +581,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       case 113: try { try decoder.decodeSingularInt32Field(value: &self._m) }()
       case 126: try {
         var v: Int32?
+        if case .b2(let _v) = self.oConflictField {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oConflictField != nil {try decoder.handleConflictingOneOf()}
@@ -582,6 +590,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       }()
       case 201: try {
         var v: Int32?
+        if case .a3(let _v) = self.oConflictExtensionsStart {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oConflictExtensionsStart != nil {try decoder.handleConflictingOneOf()}
@@ -590,6 +599,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       }()
       case 226: try {
         var v: Int32?
+        if case .b3(let _v) = self.oConflictExtensionsStart {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oConflictExtensionsStart != nil {try decoder.handleConflictingOneOf()}
@@ -598,6 +608,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       }()
       case 301: try {
         var v: Int32?
+        if case .a4(let _v) = self.oConflictExtensionsEnd {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oConflictExtensionsEnd != nil {try decoder.handleConflictingOneOf()}
@@ -606,6 +617,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       }()
       case 326: try {
         var v: Int32?
+        if case .b4(let _v) = self.oConflictExtensionsEnd {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oConflictExtensionsEnd != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufTests/unittest_swift_naming.pb.swift b/Reference/SwiftProtobufTests/unittest_swift_naming.pb.swift
index 64895f7ab..5f2348383 100644
--- a/Reference/SwiftProtobufTests/unittest_swift_naming.pb.swift
+++ b/Reference/SwiftProtobufTests/unittest_swift_naming.pb.swift
@@ -26901,6 +26901,7 @@ extension SwiftProtoTesting_Names_ValidIdentifiers: SwiftProtobuf.Message, Swift
       case 3: try { try decoder.decodeSingularInt32Field(value: &self.__3Field3) }()
       case 4: try {
         var v: Int32?
+        if case ._4(let _v) = self._2Of {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self._2Of != nil {try decoder.handleConflictingOneOf()}
@@ -26909,6 +26910,7 @@ extension SwiftProtoTesting_Names_ValidIdentifiers: SwiftProtobuf.Message, Swift
       }()
       case 5: try {
         var v: Int32?
+        if case ._5Field(let _v) = self._2Of {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self._2Of != nil {try decoder.handleConflictingOneOf()}
@@ -26986,6 +26988,7 @@ extension SwiftProtoTesting_Names_SpecialNames1: SwiftProtobuf.Message, SwiftPro
       switch fieldNumber {
       case 1: try {
         var v: String?
+        if case .str(let _v) = self.newValue {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.newValue != nil {try decoder.handleConflictingOneOf()}
@@ -27089,6 +27092,7 @@ extension SwiftProtoTesting_Names_SpecialNames3: SwiftProtobuf.Message, SwiftPro
         switch fieldNumber {
         case 1: try {
           var v: String?
+          if case .str(let _v) = _storage._newValue {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._newValue != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufTests/unittest_swift_oneof_all_required.pb.swift b/Reference/SwiftProtobufTests/unittest_swift_oneof_all_required.pb.swift
index e0359e8c1..4f88a0b61 100644
--- a/Reference/SwiftProtobufTests/unittest_swift_oneof_all_required.pb.swift
+++ b/Reference/SwiftProtobufTests/unittest_swift_oneof_all_required.pb.swift
@@ -343,6 +343,7 @@ extension SwiftProtoTesting_OneOfContainer: SwiftProtobuf.Message, SwiftProtobuf
       }()
       case 6: try {
         var v: Int32?
+        if case .option4(let _v) = self.option {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.option != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufTests/unittest_swift_oneof_merging.pb.swift b/Reference/SwiftProtobufTests/unittest_swift_oneof_merging.pb.swift
index 77599c68e..1a6473353 100644
--- a/Reference/SwiftProtobufTests/unittest_swift_oneof_merging.pb.swift
+++ b/Reference/SwiftProtobufTests/unittest_swift_oneof_merging.pb.swift
@@ -189,6 +189,7 @@ extension SwiftProtoTesting_Merging_TestMessage: SwiftProtobuf.Message, SwiftPro
       switch fieldNumber {
       case 111: try {
         var v: UInt32?
+        if case .oneofUint32(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularUInt32Field(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -210,6 +211,7 @@ extension SwiftProtoTesting_Merging_TestMessage: SwiftProtobuf.Message, SwiftPro
       }()
       case 113: try {
         var v: String?
+        if case .oneofString(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -218,6 +220,7 @@ extension SwiftProtoTesting_Merging_TestMessage: SwiftProtobuf.Message, SwiftPro
       }()
       case 114: try {
         var v: Data?
+        if case .oneofBytes(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufTests/unittest_swift_runtime_proto2.pb.swift b/Reference/SwiftProtobufTests/unittest_swift_runtime_proto2.pb.swift
index f6a7786ae..440266aee 100644
--- a/Reference/SwiftProtobufTests/unittest_swift_runtime_proto2.pb.swift
+++ b/Reference/SwiftProtobufTests/unittest_swift_runtime_proto2.pb.swift
@@ -1059,6 +1059,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         case 49: try { try decoder.decodeRepeatedEnumField(value: &_storage._repeatedEnum) }()
         case 51: try {
           var v: Int32?
+          if case .oneofInt32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1067,6 +1068,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 52: try {
           var v: Int64?
+          if case .oneofInt64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1075,6 +1077,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 53: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1083,6 +1086,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 54: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1091,6 +1095,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 55: try {
           var v: Int32?
+          if case .oneofSint32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1099,6 +1104,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 56: try {
           var v: Int64?
+          if case .oneofSint64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1107,6 +1113,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 57: try {
           var v: UInt32?
+          if case .oneofFixed32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFixed32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1115,6 +1122,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 58: try {
           var v: UInt64?
+          if case .oneofFixed64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFixed64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1123,6 +1131,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 59: try {
           var v: Int32?
+          if case .oneofSfixed32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSFixed32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1131,6 +1140,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 60: try {
           var v: Int64?
+          if case .oneofSfixed64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSFixed64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1139,6 +1149,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 61: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1147,6 +1158,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 62: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1155,6 +1167,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 63: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1163,6 +1176,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 64: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1171,6 +1185,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 65: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1205,6 +1220,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 69: try {
           var v: SwiftProtoTesting_Message2.Enum?
+          if case .oneofEnum(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/SwiftProtobufTests/unittest_swift_runtime_proto3.pb.swift b/Reference/SwiftProtobufTests/unittest_swift_runtime_proto3.pb.swift
index 55e622b16..262bc6637 100644
--- a/Reference/SwiftProtobufTests/unittest_swift_runtime_proto3.pb.swift
+++ b/Reference/SwiftProtobufTests/unittest_swift_runtime_proto3.pb.swift
@@ -863,6 +863,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         case 49: try { try decoder.decodeRepeatedEnumField(value: &_storage._repeatedEnum) }()
         case 51: try {
           var v: Int32?
+          if case .oneofInt32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -871,6 +872,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 52: try {
           var v: Int64?
+          if case .oneofInt64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -879,6 +881,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 53: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -887,6 +890,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 54: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -895,6 +899,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 55: try {
           var v: Int32?
+          if case .oneofSint32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -903,6 +908,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 56: try {
           var v: Int64?
+          if case .oneofSint64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -911,6 +917,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 57: try {
           var v: UInt32?
+          if case .oneofFixed32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFixed32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -919,6 +926,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 58: try {
           var v: UInt64?
+          if case .oneofFixed64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFixed64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -927,6 +935,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 59: try {
           var v: Int32?
+          if case .oneofSfixed32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSFixed32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -935,6 +944,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 60: try {
           var v: Int64?
+          if case .oneofSfixed64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSFixed64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -943,6 +953,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 61: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -951,6 +962,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 62: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -959,6 +971,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 63: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -967,6 +980,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 64: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -975,6 +989,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 65: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -996,6 +1011,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 69: try {
           var v: SwiftProtoTesting_Message3.Enum?
+          if case .oneofEnum(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/conformance/conformance.pb.swift b/Reference/upstream/conformance/conformance.pb.swift
index ef099db7b..cea6cf759 100644
--- a/Reference/upstream/conformance/conformance.pb.swift
+++ b/Reference/upstream/conformance/conformance.pb.swift
@@ -491,6 +491,7 @@ extension Conformance_ConformanceRequest: SwiftProtobuf.Message, SwiftProtobuf._
       switch fieldNumber {
       case 1: try {
         var v: Data?
+        if case .protobufPayload(let _v) = self.payload {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.payload != nil {try decoder.handleConflictingOneOf()}
@@ -499,6 +500,7 @@ extension Conformance_ConformanceRequest: SwiftProtobuf.Message, SwiftProtobuf._
       }()
       case 2: try {
         var v: String?
+        if case .jsonPayload(let _v) = self.payload {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.payload != nil {try decoder.handleConflictingOneOf()}
@@ -511,6 +513,7 @@ extension Conformance_ConformanceRequest: SwiftProtobuf.Message, SwiftProtobuf._
       case 6: try { try decoder.decodeSingularMessageField(value: &self._jspbEncodingOptions) }()
       case 7: try {
         var v: String?
+        if case .jspbPayload(let _v) = self.payload {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.payload != nil {try decoder.handleConflictingOneOf()}
@@ -519,6 +522,7 @@ extension Conformance_ConformanceRequest: SwiftProtobuf.Message, SwiftProtobuf._
       }()
       case 8: try {
         var v: String?
+        if case .textPayload(let _v) = self.payload {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.payload != nil {try decoder.handleConflictingOneOf()}
@@ -610,6 +614,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       switch fieldNumber {
       case 1: try {
         var v: String?
+        if case .parseError(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -618,6 +623,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 2: try {
         var v: String?
+        if case .runtimeError(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -626,6 +632,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 3: try {
         var v: Data?
+        if case .protobufPayload(let _v) = self.result {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -634,6 +641,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 4: try {
         var v: String?
+        if case .jsonPayload(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -642,6 +650,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 5: try {
         var v: String?
+        if case .skipped(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -650,6 +659,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 6: try {
         var v: String?
+        if case .serializeError(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -658,6 +668,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 7: try {
         var v: String?
+        if case .jspbPayload(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -666,6 +677,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 8: try {
         var v: String?
+        if case .textPayload(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -674,6 +686,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 9: try {
         var v: String?
+        if case .timeoutError(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/struct.pb.swift b/Reference/upstream/google/protobuf/struct.pb.swift
index fd0afcc0c..ece59f97f 100644
--- a/Reference/upstream/google/protobuf/struct.pb.swift
+++ b/Reference/upstream/google/protobuf/struct.pb.swift
@@ -273,6 +273,7 @@ extension Google_Protobuf_Value: Message, _MessageImplementationBase, _ProtoName
       switch fieldNumber {
       case 1: try {
         var v: Google_Protobuf_NullValue?
+        if case .nullValue(let _v) = self.kind {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.kind != nil {try decoder.handleConflictingOneOf()}
@@ -281,6 +282,7 @@ extension Google_Protobuf_Value: Message, _MessageImplementationBase, _ProtoName
       }()
       case 2: try {
         var v: Double?
+        if case .numberValue(let _v) = self.kind {v = _v}
         try decoder.decodeSingularDoubleField(value: &v)
         if let v = v {
           if self.kind != nil {try decoder.handleConflictingOneOf()}
@@ -289,6 +291,7 @@ extension Google_Protobuf_Value: Message, _MessageImplementationBase, _ProtoName
       }()
       case 3: try {
         var v: String?
+        if case .stringValue(let _v) = self.kind {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.kind != nil {try decoder.handleConflictingOneOf()}
@@ -297,6 +300,7 @@ extension Google_Protobuf_Value: Message, _MessageImplementationBase, _ProtoName
       }()
       case 4: try {
         var v: Bool?
+        if case .boolValue(let _v) = self.kind {v = _v}
         try decoder.decodeSingularBoolField(value: &v)
         if let v = v {
           if self.kind != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/test_messages_proto2.pb.swift b/Reference/upstream/google/protobuf/test_messages_proto2.pb.swift
index 08e6faeb1..5ae2c7845 100644
--- a/Reference/upstream/google/protobuf/test_messages_proto2.pb.swift
+++ b/Reference/upstream/google/protobuf/test_messages_proto2.pb.swift
@@ -2616,6 +2616,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         case 102: try { try decoder.decodeRepeatedEnumField(value: &_storage._unpackedNestedEnum) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2637,6 +2638,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2645,6 +2647,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2653,6 +2656,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 115: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2661,6 +2665,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 116: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2669,6 +2674,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 117: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2677,6 +2683,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 118: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2685,6 +2692,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 119: try {
           var v: ProtobufTestMessages_Proto2_TestAllTypesProto2.NestedEnum?
+          if case .oneofEnum(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/test_messages_proto3.pb.swift b/Reference/upstream/google/protobuf/test_messages_proto3.pb.swift
index 367b0dc91..87afba6bf 100644
--- a/Reference/upstream/google/protobuf/test_messages_proto3.pb.swift
+++ b/Reference/upstream/google/protobuf/test_messages_proto3.pb.swift
@@ -1743,6 +1743,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         case 102: try { try decoder.decodeRepeatedEnumField(value: &_storage._unpackedNestedEnum) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1764,6 +1765,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1772,6 +1774,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1780,6 +1783,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 115: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1788,6 +1792,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 116: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1796,6 +1801,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 117: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1804,6 +1810,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 118: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1812,6 +1819,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 119: try {
           var v: ProtobufTestMessages_Proto3_TestAllTypesProto3.NestedEnum?
+          if case .oneofEnum(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1820,6 +1828,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 120: try {
           var v: SwiftProtobuf.Google_Protobuf_NullValue?
+          if case .oneofNullValue(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/unittest.pb.swift b/Reference/upstream/google/protobuf/unittest.pb.swift
index 319508562..5a91efc4d 100644
--- a/Reference/upstream/google/protobuf/unittest.pb.swift
+++ b/Reference/upstream/google/protobuf/unittest.pb.swift
@@ -10500,6 +10500,7 @@ extension ProtobufUnittest_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf._M
         case 85: try { try decoder.decodeSingularStringField(value: &_storage._defaultCord) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -10521,6 +10522,7 @@ extension ProtobufUnittest_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf._M
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -10529,6 +10531,7 @@ extension ProtobufUnittest_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf._M
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -11138,6 +11141,7 @@ extension ProtobufUnittest_TestDeprecatedFields: SwiftProtobuf.Message, SwiftPro
         case 1: try { try decoder.decodeSingularInt32Field(value: &_storage._deprecatedInt32) }()
         case 2: try {
           var v: Int32?
+          if case .deprecatedInt32InOneof(let _v) = _storage._oneofFields {v = _v}
           try decoder.decodeSingularInt32Field(value: &v)
           if let v = v {
             if _storage._oneofFields != nil {try decoder.handleConflictingOneOf()}
@@ -14915,6 +14919,7 @@ extension ProtobufUnittest_TestOneof: SwiftProtobuf.Message, SwiftProtobuf._Mess
       switch fieldNumber {
       case 1: try {
         var v: Int32?
+        if case .fooInt(let _v) = self.foo {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -14923,6 +14928,7 @@ extension ProtobufUnittest_TestOneof: SwiftProtobuf.Message, SwiftProtobuf._Mess
       }()
       case 2: try {
         var v: String?
+        if case .fooString(let _v) = self.foo {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -15167,6 +15173,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       switch fieldNumber {
       case 1: try {
         var v: Int32?
+        if case .fooInt(let _v) = self.foo {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -15175,6 +15182,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 2: try {
         var v: String?
+        if case .fooString(let _v) = self.foo {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -15183,6 +15191,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 3: try {
         var v: String?
+        if case .fooCord(let _v) = self.foo {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -15191,6 +15200,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 4: try {
         var v: String?
+        if case .fooStringPiece(let _v) = self.foo {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -15199,6 +15209,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 5: try {
         var v: Data?
+        if case .fooBytes(let _v) = self.foo {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -15207,6 +15218,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 6: try {
         var v: ProtobufUnittest_TestOneof2.NestedEnum?
+        if case .fooEnum(let _v) = self.foo {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -15254,6 +15266,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 12: try {
         var v: Int32?
+        if case .barInt(let _v) = self.bar {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.bar != nil {try decoder.handleConflictingOneOf()}
@@ -15262,6 +15275,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 13: try {
         var v: String?
+        if case .barString(let _v) = self.bar {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.bar != nil {try decoder.handleConflictingOneOf()}
@@ -15270,6 +15284,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 14: try {
         var v: String?
+        if case .barCord(let _v) = self.bar {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.bar != nil {try decoder.handleConflictingOneOf()}
@@ -15278,6 +15293,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 15: try {
         var v: String?
+        if case .barStringPiece(let _v) = self.bar {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.bar != nil {try decoder.handleConflictingOneOf()}
@@ -15286,6 +15302,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 16: try {
         var v: Data?
+        if case .barBytes(let _v) = self.bar {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.bar != nil {try decoder.handleConflictingOneOf()}
@@ -15294,6 +15311,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 17: try {
         var v: ProtobufUnittest_TestOneof2.NestedEnum?
+        if case .barEnum(let _v) = self.bar {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.bar != nil {try decoder.handleConflictingOneOf()}
@@ -15304,6 +15322,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       case 19: try { try decoder.decodeSingularStringField(value: &self._bazString) }()
       case 20: try {
         var v: String?
+        if case .barStringWithEmptyDefault(let _v) = self.bar {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.bar != nil {try decoder.handleConflictingOneOf()}
@@ -15312,6 +15331,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 21: try {
         var v: String?
+        if case .barCordWithEmptyDefault(let _v) = self.bar {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.bar != nil {try decoder.handleConflictingOneOf()}
@@ -15320,6 +15340,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 22: try {
         var v: String?
+        if case .barStringPieceWithEmptyDefault(let _v) = self.bar {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.bar != nil {try decoder.handleConflictingOneOf()}
@@ -15328,6 +15349,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 23: try {
         var v: Data?
+        if case .barBytesWithEmptyDefault(let _v) = self.bar {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.bar != nil {try decoder.handleConflictingOneOf()}
@@ -15336,6 +15358,7 @@ extension ProtobufUnittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 30: try {
         var v: Data?
+        if case .fooBytesCord(let _v) = self.foo {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -15573,6 +15596,7 @@ extension ProtobufUnittest_TestRequiredOneof: SwiftProtobuf.Message, SwiftProtob
       switch fieldNumber {
       case 1: try {
         var v: Int32?
+        if case .fooInt(let _v) = self.foo {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -15581,6 +15605,7 @@ extension ProtobufUnittest_TestRequiredOneof: SwiftProtobuf.Message, SwiftProtob
       }()
       case 2: try {
         var v: String?
+        if case .fooString(let _v) = self.foo {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -16852,6 +16877,7 @@ extension ProtobufUnittest_TestHugeFieldNumbers: SwiftProtobuf.Message, SwiftPro
       case 536870010: try { try decoder.decodeMapField(fieldType: SwiftProtobuf._ProtobufMap<SwiftProtobuf.ProtobufString,SwiftProtobuf.ProtobufString>.self, value: &self.stringStringMap) }()
       case 536870011: try {
         var v: UInt32?
+        if case .oneofUint32(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularUInt32Field(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -16873,6 +16899,7 @@ extension ProtobufUnittest_TestHugeFieldNumbers: SwiftProtobuf.Message, SwiftPro
       }()
       case 536870013: try {
         var v: String?
+        if case .oneofString(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -16881,6 +16908,7 @@ extension ProtobufUnittest_TestHugeFieldNumbers: SwiftProtobuf.Message, SwiftPro
       }()
       case 536870014: try {
         var v: Data?
+        if case .oneofBytes(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/unittest_custom_options.pb.swift b/Reference/upstream/google/protobuf/unittest_custom_options.pb.swift
index d175ae0ec..f64b2d149 100644
--- a/Reference/upstream/google/protobuf/unittest_custom_options.pb.swift
+++ b/Reference/upstream/google/protobuf/unittest_custom_options.pb.swift
@@ -1863,6 +1863,7 @@ extension ProtobufUnittest_TestMessageWithCustomOptions: SwiftProtobuf.Message,
       case 1: try { try decoder.decodeSingularStringField(value: &self._field1) }()
       case 2: try {
         var v: Int32?
+        if case .oneofField(let _v) = self.anOneof {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.anOneof != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/unittest_lite.pb.swift b/Reference/upstream/google/protobuf/unittest_lite.pb.swift
index 092996ba7..ec9acf778 100644
--- a/Reference/upstream/google/protobuf/unittest_lite.pb.swift
+++ b/Reference/upstream/google/protobuf/unittest_lite.pb.swift
@@ -3727,6 +3727,7 @@ extension ProtobufUnittest_TestAllTypesLite: SwiftProtobuf.Message, SwiftProtobu
         case 85: try { try decoder.decodeSingularStringField(value: &_storage._defaultCord) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -3748,6 +3749,7 @@ extension ProtobufUnittest_TestAllTypesLite: SwiftProtobuf.Message, SwiftProtobu
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -3756,6 +3758,7 @@ extension ProtobufUnittest_TestAllTypesLite: SwiftProtobuf.Message, SwiftProtobu
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -5204,6 +5207,7 @@ extension ProtobufUnittest_TestHugeFieldNumbersLite: SwiftProtobuf.Message, Swif
       case 536870010: try { try decoder.decodeMapField(fieldType: SwiftProtobuf._ProtobufMap<SwiftProtobuf.ProtobufString,SwiftProtobuf.ProtobufString>.self, value: &self.stringStringMap) }()
       case 536870011: try {
         var v: UInt32?
+        if case .oneofUint32(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularUInt32Field(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -5225,6 +5229,7 @@ extension ProtobufUnittest_TestHugeFieldNumbersLite: SwiftProtobuf.Message, Swif
       }()
       case 536870013: try {
         var v: String?
+        if case .oneofString(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -5233,6 +5238,7 @@ extension ProtobufUnittest_TestHugeFieldNumbersLite: SwiftProtobuf.Message, Swif
       }()
       case 536870014: try {
         var v: Data?
+        if case .oneofBytes(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -5380,6 +5386,7 @@ extension ProtobufUnittest_TestOneofParsingLite: SwiftProtobuf.Message, SwiftPro
       switch fieldNumber {
       case 1: try {
         var v: Int32?
+        if case .oneofInt32(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -5401,6 +5408,7 @@ extension ProtobufUnittest_TestOneofParsingLite: SwiftProtobuf.Message, SwiftPro
       }()
       case 3: try {
         var v: String?
+        if case .oneofString(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -5409,6 +5417,7 @@ extension ProtobufUnittest_TestOneofParsingLite: SwiftProtobuf.Message, SwiftPro
       }()
       case 4: try {
         var v: Data?
+        if case .oneofBytes(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -5417,6 +5426,7 @@ extension ProtobufUnittest_TestOneofParsingLite: SwiftProtobuf.Message, SwiftPro
       }()
       case 5: try {
         var v: String?
+        if case .oneofStringCord(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -5425,6 +5435,7 @@ extension ProtobufUnittest_TestOneofParsingLite: SwiftProtobuf.Message, SwiftPro
       }()
       case 6: try {
         var v: Data?
+        if case .oneofBytesCord(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -5433,6 +5444,7 @@ extension ProtobufUnittest_TestOneofParsingLite: SwiftProtobuf.Message, SwiftPro
       }()
       case 7: try {
         var v: String?
+        if case .oneofStringStringPiece(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -5441,6 +5453,7 @@ extension ProtobufUnittest_TestOneofParsingLite: SwiftProtobuf.Message, SwiftPro
       }()
       case 8: try {
         var v: Data?
+        if case .oneofBytesStringPiece(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -5449,6 +5462,7 @@ extension ProtobufUnittest_TestOneofParsingLite: SwiftProtobuf.Message, SwiftPro
       }()
       case 9: try {
         var v: ProtobufUnittest_V2EnumLite?
+        if case .oneofEnum(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/unittest_no_field_presence.pb.swift b/Reference/upstream/google/protobuf/unittest_no_field_presence.pb.swift
index 5ebf33814..fbea87849 100644
--- a/Reference/upstream/google/protobuf/unittest_no_field_presence.pb.swift
+++ b/Reference/upstream/google/protobuf/unittest_no_field_presence.pb.swift
@@ -722,6 +722,7 @@ extension Proto2NofieldpresenceUnittest_TestAllTypes: SwiftProtobuf.Message, Swi
         case 57: try { try decoder.decodeRepeatedMessageField(value: &_storage._repeatedLazyMessage) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -743,6 +744,7 @@ extension Proto2NofieldpresenceUnittest_TestAllTypes: SwiftProtobuf.Message, Swi
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -751,6 +753,7 @@ extension Proto2NofieldpresenceUnittest_TestAllTypes: SwiftProtobuf.Message, Swi
         }()
         case 114: try {
           var v: Proto2NofieldpresenceUnittest_TestAllTypes.NestedEnum?
+          if case .oneofEnum(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/unittest_optimize_for.pb.swift b/Reference/upstream/google/protobuf/unittest_optimize_for.pb.swift
index c0620b0e5..752279735 100644
--- a/Reference/upstream/google/protobuf/unittest_optimize_for.pb.swift
+++ b/Reference/upstream/google/protobuf/unittest_optimize_for.pb.swift
@@ -253,6 +253,7 @@ extension ProtobufUnittest_TestOptimizedForSize: SwiftProtobuf.Message, SwiftPro
       case 1: try { try decoder.decodeSingularInt32Field(value: &self._i) }()
       case 2: try {
         var v: Int32?
+        if case .integerField(let _v) = self.foo {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -261,6 +262,7 @@ extension ProtobufUnittest_TestOptimizedForSize: SwiftProtobuf.Message, SwiftPro
       }()
       case 3: try {
         var v: String?
+        if case .stringField(let _v) = self.foo {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/unittest_preserve_unknown_enum.pb.swift b/Reference/upstream/google/protobuf/unittest_preserve_unknown_enum.pb.swift
index 58ba6c1c6..74fb0aee8 100644
--- a/Reference/upstream/google/protobuf/unittest_preserve_unknown_enum.pb.swift
+++ b/Reference/upstream/google/protobuf/unittest_preserve_unknown_enum.pb.swift
@@ -259,6 +259,7 @@ extension Proto3PreserveUnknownEnumUnittest_MyMessage: SwiftProtobuf.Message, Sw
       case 4: try { try decoder.decodeRepeatedEnumField(value: &self.repeatedPackedUnexpectedE) }()
       case 5: try {
         var v: Proto3PreserveUnknownEnumUnittest_MyEnum?
+        if case .oneofE1(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -267,6 +268,7 @@ extension Proto3PreserveUnknownEnumUnittest_MyMessage: SwiftProtobuf.Message, Sw
       }()
       case 6: try {
         var v: Proto3PreserveUnknownEnumUnittest_MyEnum?
+        if case .oneofE2(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -343,6 +345,7 @@ extension Proto3PreserveUnknownEnumUnittest_MyMessagePlusExtra: SwiftProtobuf.Me
       case 4: try { try decoder.decodeRepeatedEnumField(value: &self.repeatedPackedUnexpectedE) }()
       case 5: try {
         var v: Proto3PreserveUnknownEnumUnittest_MyEnumPlusExtra?
+        if case .oneofE1(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -351,6 +354,7 @@ extension Proto3PreserveUnknownEnumUnittest_MyMessagePlusExtra: SwiftProtobuf.Me
       }()
       case 6: try {
         var v: Proto3PreserveUnknownEnumUnittest_MyEnumPlusExtra?
+        if case .oneofE2(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/unittest_preserve_unknown_enum2.pb.swift b/Reference/upstream/google/protobuf/unittest_preserve_unknown_enum2.pb.swift
index 7422ab11d..d98e616b2 100644
--- a/Reference/upstream/google/protobuf/unittest_preserve_unknown_enum2.pb.swift
+++ b/Reference/upstream/google/protobuf/unittest_preserve_unknown_enum2.pb.swift
@@ -166,6 +166,7 @@ extension Proto2PreserveUnknownEnumUnittest_MyMessage: SwiftProtobuf.Message, Sw
       case 4: try { try decoder.decodeRepeatedEnumField(value: &self.repeatedPackedUnexpectedE) }()
       case 5: try {
         var v: Proto2PreserveUnknownEnumUnittest_MyEnum?
+        if case .oneofE1(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -174,6 +175,7 @@ extension Proto2PreserveUnknownEnumUnittest_MyMessage: SwiftProtobuf.Message, Sw
       }()
       case 6: try {
         var v: Proto2PreserveUnknownEnumUnittest_MyEnum?
+        if case .oneofE2(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/unittest_proto3.pb.swift b/Reference/upstream/google/protobuf/unittest_proto3.pb.swift
index 5a5215119..7c8b27054 100644
--- a/Reference/upstream/google/protobuf/unittest_proto3.pb.swift
+++ b/Reference/upstream/google/protobuf/unittest_proto3.pb.swift
@@ -953,6 +953,7 @@ extension Proto3Unittest_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf._Mes
         case 57: try { try decoder.decodeRepeatedMessageField(value: &_storage._repeatedLazyMessage) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -974,6 +975,7 @@ extension Proto3Unittest_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf._Mes
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -982,6 +984,7 @@ extension Proto3Unittest_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf._Mes
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1670,6 +1673,7 @@ extension Proto3Unittest_TestOneof2: SwiftProtobuf.Message, SwiftProtobuf._Messa
       switch fieldNumber {
       case 6: try {
         var v: Proto3Unittest_TestOneof2.NestedEnum?
+        if case .fooEnum(let _v) = self.foo {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/unittest_proto3_arena.pb.swift b/Reference/upstream/google/protobuf/unittest_proto3_arena.pb.swift
index c74e3d4f0..48e7749b3 100644
--- a/Reference/upstream/google/protobuf/unittest_proto3_arena.pb.swift
+++ b/Reference/upstream/google/protobuf/unittest_proto3_arena.pb.swift
@@ -1099,6 +1099,7 @@ extension Proto3ArenaUnittest_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf
         case 57: try { try decoder.decodeRepeatedMessageField(value: &_storage._repeatedLazyMessage) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1120,6 +1121,7 @@ extension Proto3ArenaUnittest_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1128,6 +1130,7 @@ extension Proto3ArenaUnittest_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/unittest_proto3_arena_lite.pb.swift b/Reference/upstream/google/protobuf/unittest_proto3_arena_lite.pb.swift
index 7c46b2cf0..a4a2dcd51 100644
--- a/Reference/upstream/google/protobuf/unittest_proto3_arena_lite.pb.swift
+++ b/Reference/upstream/google/protobuf/unittest_proto3_arena_lite.pb.swift
@@ -821,6 +821,7 @@ extension Proto3ArenaLiteUnittest_TestAllTypes: SwiftProtobuf.Message, SwiftProt
         case 57: try { try decoder.decodeRepeatedMessageField(value: &_storage._repeatedLazyMessage) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -842,6 +843,7 @@ extension Proto3ArenaLiteUnittest_TestAllTypes: SwiftProtobuf.Message, SwiftProt
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -850,6 +852,7 @@ extension Proto3ArenaLiteUnittest_TestAllTypes: SwiftProtobuf.Message, SwiftProt
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/unittest_proto3_lite.pb.swift b/Reference/upstream/google/protobuf/unittest_proto3_lite.pb.swift
index 68bc0aa0a..e61804021 100644
--- a/Reference/upstream/google/protobuf/unittest_proto3_lite.pb.swift
+++ b/Reference/upstream/google/protobuf/unittest_proto3_lite.pb.swift
@@ -821,6 +821,7 @@ extension Proto3LiteUnittest_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf.
         case 57: try { try decoder.decodeRepeatedMessageField(value: &_storage._repeatedLazyMessage) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -842,6 +843,7 @@ extension Proto3LiteUnittest_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf.
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -850,6 +852,7 @@ extension Proto3LiteUnittest_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf.
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Reference/upstream/google/protobuf/unittest_retention.pb.swift b/Reference/upstream/google/protobuf/unittest_retention.pb.swift
index 005f37f9e..80c6a76bb 100644
--- a/Reference/upstream/google/protobuf/unittest_retention.pb.swift
+++ b/Reference/upstream/google/protobuf/unittest_retention.pb.swift
@@ -667,6 +667,7 @@ extension ProtobufUnittest_TopLevelMessage: SwiftProtobuf.Message, SwiftProtobuf
       case 1: try { try decoder.decodeSingularFloatField(value: &self._f) }()
       case 2: try {
         var v: Int64?
+        if case .i(let _v) = self.o {v = _v}
         try decoder.decodeSingularInt64Field(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Sources/Conformance/conformance.pb.swift b/Sources/Conformance/conformance.pb.swift
index ef099db7b..cea6cf759 100644
--- a/Sources/Conformance/conformance.pb.swift
+++ b/Sources/Conformance/conformance.pb.swift
@@ -491,6 +491,7 @@ extension Conformance_ConformanceRequest: SwiftProtobuf.Message, SwiftProtobuf._
       switch fieldNumber {
       case 1: try {
         var v: Data?
+        if case .protobufPayload(let _v) = self.payload {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.payload != nil {try decoder.handleConflictingOneOf()}
@@ -499,6 +500,7 @@ extension Conformance_ConformanceRequest: SwiftProtobuf.Message, SwiftProtobuf._
       }()
       case 2: try {
         var v: String?
+        if case .jsonPayload(let _v) = self.payload {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.payload != nil {try decoder.handleConflictingOneOf()}
@@ -511,6 +513,7 @@ extension Conformance_ConformanceRequest: SwiftProtobuf.Message, SwiftProtobuf._
       case 6: try { try decoder.decodeSingularMessageField(value: &self._jspbEncodingOptions) }()
       case 7: try {
         var v: String?
+        if case .jspbPayload(let _v) = self.payload {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.payload != nil {try decoder.handleConflictingOneOf()}
@@ -519,6 +522,7 @@ extension Conformance_ConformanceRequest: SwiftProtobuf.Message, SwiftProtobuf._
       }()
       case 8: try {
         var v: String?
+        if case .textPayload(let _v) = self.payload {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.payload != nil {try decoder.handleConflictingOneOf()}
@@ -610,6 +614,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       switch fieldNumber {
       case 1: try {
         var v: String?
+        if case .parseError(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -618,6 +623,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 2: try {
         var v: String?
+        if case .runtimeError(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -626,6 +632,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 3: try {
         var v: Data?
+        if case .protobufPayload(let _v) = self.result {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -634,6 +641,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 4: try {
         var v: String?
+        if case .jsonPayload(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -642,6 +650,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 5: try {
         var v: String?
+        if case .skipped(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -650,6 +659,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 6: try {
         var v: String?
+        if case .serializeError(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -658,6 +668,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 7: try {
         var v: String?
+        if case .jspbPayload(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -666,6 +677,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 8: try {
         var v: String?
+        if case .textPayload(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
@@ -674,6 +686,7 @@ extension Conformance_ConformanceResponse: SwiftProtobuf.Message, SwiftProtobuf.
       }()
       case 9: try {
         var v: String?
+        if case .timeoutError(let _v) = self.result {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.result != nil {try decoder.handleConflictingOneOf()}
diff --git a/Sources/Conformance/test_messages_proto2.pb.swift b/Sources/Conformance/test_messages_proto2.pb.swift
index 08e6faeb1..5ae2c7845 100644
--- a/Sources/Conformance/test_messages_proto2.pb.swift
+++ b/Sources/Conformance/test_messages_proto2.pb.swift
@@ -2616,6 +2616,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         case 102: try { try decoder.decodeRepeatedEnumField(value: &_storage._unpackedNestedEnum) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2637,6 +2638,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2645,6 +2647,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2653,6 +2656,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 115: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2661,6 +2665,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 116: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2669,6 +2674,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 117: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2677,6 +2683,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 118: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -2685,6 +2692,7 @@ extension ProtobufTestMessages_Proto2_TestAllTypesProto2: SwiftProtobuf.Message,
         }()
         case 119: try {
           var v: ProtobufTestMessages_Proto2_TestAllTypesProto2.NestedEnum?
+          if case .oneofEnum(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Sources/Conformance/test_messages_proto3.pb.swift b/Sources/Conformance/test_messages_proto3.pb.swift
index 367b0dc91..87afba6bf 100644
--- a/Sources/Conformance/test_messages_proto3.pb.swift
+++ b/Sources/Conformance/test_messages_proto3.pb.swift
@@ -1743,6 +1743,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         case 102: try { try decoder.decodeRepeatedEnumField(value: &_storage._unpackedNestedEnum) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1764,6 +1765,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1772,6 +1774,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1780,6 +1783,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 115: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1788,6 +1792,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 116: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1796,6 +1801,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 117: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1804,6 +1810,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 118: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1812,6 +1819,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 119: try {
           var v: ProtobufTestMessages_Proto3_TestAllTypesProto3.NestedEnum?
+          if case .oneofEnum(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1820,6 +1828,7 @@ extension ProtobufTestMessages_Proto3_TestAllTypesProto3: SwiftProtobuf.Message,
         }()
         case 120: try {
           var v: SwiftProtobuf.Google_Protobuf_NullValue?
+          if case .oneofNullValue(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Sources/SwiftProtobuf/struct.pb.swift b/Sources/SwiftProtobuf/struct.pb.swift
index ca15b48b3..9c43f716e 100644
--- a/Sources/SwiftProtobuf/struct.pb.swift
+++ b/Sources/SwiftProtobuf/struct.pb.swift
@@ -273,6 +273,7 @@ extension Google_Protobuf_Value: Message, _MessageImplementationBase, _ProtoName
       switch fieldNumber {
       case 1: try {
         var v: Google_Protobuf_NullValue?
+        if case .nullValue(let _v) = self.kind {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.kind != nil {try decoder.handleConflictingOneOf()}
@@ -281,6 +282,7 @@ extension Google_Protobuf_Value: Message, _MessageImplementationBase, _ProtoName
       }()
       case 2: try {
         var v: Double?
+        if case .numberValue(let _v) = self.kind {v = _v}
         try decoder.decodeSingularDoubleField(value: &v)
         if let v = v {
           if self.kind != nil {try decoder.handleConflictingOneOf()}
@@ -289,6 +291,7 @@ extension Google_Protobuf_Value: Message, _MessageImplementationBase, _ProtoName
       }()
       case 3: try {
         var v: String?
+        if case .stringValue(let _v) = self.kind {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.kind != nil {try decoder.handleConflictingOneOf()}
@@ -297,6 +300,7 @@ extension Google_Protobuf_Value: Message, _MessageImplementationBase, _ProtoName
       }()
       case 4: try {
         var v: Bool?
+        if case .boolValue(let _v) = self.kind {v = _v}
         try decoder.decodeSingularBoolField(value: &v)
         if let v = v {
           if self.kind != nil {try decoder.handleConflictingOneOf()}
diff --git a/Sources/protoc-gen-swift/OneofGenerator.swift b/Sources/protoc-gen-swift/OneofGenerator.swift
index da9db37aa..a1c07eba0 100644
--- a/Sources/protoc-gen-swift/OneofGenerator.swift
+++ b/Sources/protoc-gen-swift/OneofGenerator.swift
@@ -345,6 +345,7 @@ class OneofGenerator {
               hadValueTest = "hadOneofValue"
           } else {
               p.print("var v: \(field.swiftType)?")
+              p.print("if case \(field.dottedSwiftName)(let _v) = \(storedProperty) {v = _v}")
               hadValueTest = "\(storedProperty) != nil"
           }
 
diff --git a/Tests/SwiftProtobufTests/fuzz_testing.pb.swift b/Tests/SwiftProtobufTests/fuzz_testing.pb.swift
index c4989d82f..6cca011c4 100644
--- a/Tests/SwiftProtobufTests/fuzz_testing.pb.swift
+++ b/Tests/SwiftProtobufTests/fuzz_testing.pb.swift
@@ -3471,6 +3471,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         case 49: try { try decoder.decodeRepeatedMessageField(value: &_storage._repeatedMessage) }()
         case 61: try {
           var v: Int32?
+          if case .oneofInt32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3479,6 +3480,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 62: try {
           var v: Int64?
+          if case .oneofInt64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3487,6 +3489,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 63: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3495,6 +3498,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 64: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3503,6 +3507,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 65: try {
           var v: Int32?
+          if case .oneofSint32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3511,6 +3516,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 66: try {
           var v: Int64?
+          if case .oneofSint64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3519,6 +3525,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 67: try {
           var v: UInt32?
+          if case .oneofFixed32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFixed32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3527,6 +3534,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 68: try {
           var v: UInt64?
+          if case .oneofFixed64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFixed64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3535,6 +3543,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 69: try {
           var v: Int32?
+          if case .oneofSfixed32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSFixed32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3543,6 +3552,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 70: try {
           var v: Int64?
+          if case .oneofSfixed64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSFixed64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3551,6 +3561,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 71: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3559,6 +3570,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 72: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3567,6 +3579,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 73: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3575,6 +3588,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 74: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3583,6 +3597,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 75: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -3591,6 +3606,7 @@ extension SwiftProtoTesting_Fuzz_Message: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 76: try {
           var v: SwiftProtoTesting_Fuzz_AnEnum?
+          if case .oneofEnum(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Tests/SwiftProtobufTests/test_messages_proto3.pb.swift b/Tests/SwiftProtobufTests/test_messages_proto3.pb.swift
index 23f15c768..224739838 100644
--- a/Tests/SwiftProtobufTests/test_messages_proto3.pb.swift
+++ b/Tests/SwiftProtobufTests/test_messages_proto3.pb.swift
@@ -1215,6 +1215,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         case 73: try { try decoder.decodeMapField(fieldType: SwiftProtobuf._ProtobufEnumMap<SwiftProtobuf.ProtobufString,SwiftProtoTesting_Test3_TestAllTypesProto3.NestedEnum>.self, value: &_storage._mapStringNestedEnum) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1236,6 +1237,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1244,6 +1246,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1252,6 +1255,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 115: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1260,6 +1264,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 116: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1268,6 +1273,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 117: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1276,6 +1282,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 118: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1284,6 +1291,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 119: try {
           var v: SwiftProtoTesting_Test3_TestAllTypesProto3.NestedEnum?
+          if case .oneofEnum(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1292,6 +1300,7 @@ extension SwiftProtoTesting_Test3_TestAllTypesProto3: SwiftProtobuf.Message, Swi
         }()
         case 120: try {
           var v: SwiftProtobuf.Google_Protobuf_NullValue?
+          if case .oneofNullValue(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Tests/SwiftProtobufTests/unittest.pb.swift b/Tests/SwiftProtobufTests/unittest.pb.swift
index 28c5d01de..aa1abfaf3 100644
--- a/Tests/SwiftProtobufTests/unittest.pb.swift
+++ b/Tests/SwiftProtobufTests/unittest.pb.swift
@@ -4298,6 +4298,7 @@ extension SwiftProtoTesting_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf._
         case 85: try { try decoder.decodeSingularStringField(value: &_storage._defaultCord) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -4319,6 +4320,7 @@ extension SwiftProtoTesting_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -4327,6 +4329,7 @@ extension SwiftProtoTesting_TestAllTypes: SwiftProtobuf.Message, SwiftProtobuf._
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -6043,6 +6046,7 @@ extension SwiftProtoTesting_TestOneof: SwiftProtobuf.Message, SwiftProtobuf._Mes
       switch fieldNumber {
       case 1: try {
         var v: Int32?
+        if case .fooInt(let _v) = self.foo {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -6051,6 +6055,7 @@ extension SwiftProtoTesting_TestOneof: SwiftProtobuf.Message, SwiftProtobuf._Mes
       }()
       case 2: try {
         var v: String?
+        if case .fooString(let _v) = self.foo {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -6186,6 +6191,7 @@ extension SwiftProtoTesting_TestRequiredOneof: SwiftProtobuf.Message, SwiftProto
       switch fieldNumber {
       case 1: try {
         var v: Int32?
+        if case .fooInt(let _v) = self.foo {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
@@ -6194,6 +6200,7 @@ extension SwiftProtoTesting_TestRequiredOneof: SwiftProtobuf.Message, SwiftProto
       }()
       case 2: try {
         var v: String?
+        if case .fooString(let _v) = self.foo {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.foo != nil {try decoder.handleConflictingOneOf()}
diff --git a/Tests/SwiftProtobufTests/unittest_preserve_unknown_enum.pb.swift b/Tests/SwiftProtobufTests/unittest_preserve_unknown_enum.pb.swift
index aac6b31bf..8f2610962 100644
--- a/Tests/SwiftProtobufTests/unittest_preserve_unknown_enum.pb.swift
+++ b/Tests/SwiftProtobufTests/unittest_preserve_unknown_enum.pb.swift
@@ -259,6 +259,7 @@ extension SwiftProtoTesting_UnknownEnum_Proto3_MyMessage: SwiftProtobuf.Message,
       case 4: try { try decoder.decodeRepeatedEnumField(value: &self.repeatedPackedUnexpectedE) }()
       case 5: try {
         var v: SwiftProtoTesting_UnknownEnum_Proto3_MyEnum?
+        if case .oneofE1(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -267,6 +268,7 @@ extension SwiftProtoTesting_UnknownEnum_Proto3_MyMessage: SwiftProtobuf.Message,
       }()
       case 6: try {
         var v: SwiftProtoTesting_UnknownEnum_Proto3_MyEnum?
+        if case .oneofE2(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -343,6 +345,7 @@ extension SwiftProtoTesting_UnknownEnum_Proto3_MyMessagePlusExtra: SwiftProtobuf
       case 4: try { try decoder.decodeRepeatedEnumField(value: &self.repeatedPackedUnexpectedE) }()
       case 5: try {
         var v: SwiftProtoTesting_UnknownEnum_Proto3_MyEnumPlusExtra?
+        if case .oneofE1(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -351,6 +354,7 @@ extension SwiftProtoTesting_UnknownEnum_Proto3_MyMessagePlusExtra: SwiftProtobuf
       }()
       case 6: try {
         var v: SwiftProtoTesting_UnknownEnum_Proto3_MyEnumPlusExtra?
+        if case .oneofE2(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Tests/SwiftProtobufTests/unittest_preserve_unknown_enum2.pb.swift b/Tests/SwiftProtobufTests/unittest_preserve_unknown_enum2.pb.swift
index 406ca934d..5aed56231 100644
--- a/Tests/SwiftProtobufTests/unittest_preserve_unknown_enum2.pb.swift
+++ b/Tests/SwiftProtobufTests/unittest_preserve_unknown_enum2.pb.swift
@@ -166,6 +166,7 @@ extension SwiftProtoTesting_UnknownEnum_Proto2_MyMessage: SwiftProtobuf.Message,
       case 4: try { try decoder.decodeRepeatedEnumField(value: &self.repeatedPackedUnexpectedE) }()
       case 5: try {
         var v: SwiftProtoTesting_UnknownEnum_Proto2_MyEnum?
+        if case .oneofE1(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
@@ -174,6 +175,7 @@ extension SwiftProtoTesting_UnknownEnum_Proto2_MyMessage: SwiftProtobuf.Message,
       }()
       case 6: try {
         var v: SwiftProtoTesting_UnknownEnum_Proto2_MyEnum?
+        if case .oneofE2(let _v) = self.o {v = _v}
         try decoder.decodeSingularEnumField(value: &v)
         if let v = v {
           if self.o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Tests/SwiftProtobufTests/unittest_proto3.pb.swift b/Tests/SwiftProtobufTests/unittest_proto3.pb.swift
index 87f861d19..9ce663000 100644
--- a/Tests/SwiftProtobufTests/unittest_proto3.pb.swift
+++ b/Tests/SwiftProtobufTests/unittest_proto3.pb.swift
@@ -891,6 +891,7 @@ extension SwiftProtoTesting_Proto3_TestAllTypes: SwiftProtobuf.Message, SwiftPro
         case 57: try { try decoder.decodeRepeatedMessageField(value: &_storage._repeatedLazyMessage) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -912,6 +913,7 @@ extension SwiftProtoTesting_Proto3_TestAllTypes: SwiftProtobuf.Message, SwiftPro
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -920,6 +922,7 @@ extension SwiftProtoTesting_Proto3_TestAllTypes: SwiftProtobuf.Message, SwiftPro
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Tests/SwiftProtobufTests/unittest_swift_all_required_types.pb.swift b/Tests/SwiftProtobufTests/unittest_swift_all_required_types.pb.swift
index 6638e4d40..cf992c22c 100644
--- a/Tests/SwiftProtobufTests/unittest_swift_all_required_types.pb.swift
+++ b/Tests/SwiftProtobufTests/unittest_swift_all_required_types.pb.swift
@@ -989,6 +989,7 @@ extension SwiftProtoTesting_TestAllRequiredTypes: SwiftProtobuf.Message, SwiftPr
         case 85: try { try decoder.decodeSingularStringField(value: &_storage._defaultCord) }()
         case 111: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1010,6 +1011,7 @@ extension SwiftProtoTesting_TestAllRequiredTypes: SwiftProtobuf.Message, SwiftPr
         }()
         case 113: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -1018,6 +1020,7 @@ extension SwiftProtoTesting_TestAllRequiredTypes: SwiftProtobuf.Message, SwiftPr
         }()
         case 114: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._oneofField {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Tests/SwiftProtobufTests/unittest_swift_fieldorder.pb.swift b/Tests/SwiftProtobufTests/unittest_swift_fieldorder.pb.swift
index ab4754d5f..acfa9cbcd 100644
--- a/Tests/SwiftProtobufTests/unittest_swift_fieldorder.pb.swift
+++ b/Tests/SwiftProtobufTests/unittest_swift_fieldorder.pb.swift
@@ -389,6 +389,7 @@ extension SwiftProtoTesting_Order_TestFieldOrderings: SwiftProtobuf.Message, Swi
       case 1: try { try decoder.decodeSingularInt64Field(value: &self._myInt) }()
       case 9: try {
         var v: Bool?
+        if case .oneofBool(let _v) = self.options {v = _v}
         try decoder.decodeSingularBoolField(value: &v)
         if let v = v {
           if self.options != nil {try decoder.handleConflictingOneOf()}
@@ -397,6 +398,7 @@ extension SwiftProtoTesting_Order_TestFieldOrderings: SwiftProtobuf.Message, Swi
       }()
       case 10: try {
         var v: Int32?
+        if case .oneofInt32(let _v) = self.options {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.options != nil {try decoder.handleConflictingOneOf()}
@@ -406,6 +408,7 @@ extension SwiftProtoTesting_Order_TestFieldOrderings: SwiftProtobuf.Message, Swi
       case 11: try { try decoder.decodeSingularStringField(value: &self._myString) }()
       case 60: try {
         var v: Int64?
+        if case .oneofInt64(let _v) = self.options {v = _v}
         try decoder.decodeSingularInt64Field(value: &v)
         if let v = v {
           if self.options != nil {try decoder.handleConflictingOneOf()}
@@ -415,6 +418,7 @@ extension SwiftProtoTesting_Order_TestFieldOrderings: SwiftProtobuf.Message, Swi
       case 101: try { try decoder.decodeSingularFloatField(value: &self._myFloat) }()
       case 150: try {
         var v: String?
+        if case .oneofString(let _v) = self.options {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.options != nil {try decoder.handleConflictingOneOf()}
@@ -549,6 +553,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       switch fieldNumber {
       case 1: try {
         var v: Int32?
+        if case .a(let _v) = self.oGood {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oGood != nil {try decoder.handleConflictingOneOf()}
@@ -557,6 +562,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       }()
       case 26: try {
         var v: Int32?
+        if case .b(let _v) = self.oGood {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oGood != nil {try decoder.handleConflictingOneOf()}
@@ -565,6 +571,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       }()
       case 101: try {
         var v: Int32?
+        if case .a2(let _v) = self.oConflictField {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oConflictField != nil {try decoder.handleConflictingOneOf()}
@@ -574,6 +581,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       case 113: try { try decoder.decodeSingularInt32Field(value: &self._m) }()
       case 126: try {
         var v: Int32?
+        if case .b2(let _v) = self.oConflictField {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oConflictField != nil {try decoder.handleConflictingOneOf()}
@@ -582,6 +590,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       }()
       case 201: try {
         var v: Int32?
+        if case .a3(let _v) = self.oConflictExtensionsStart {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oConflictExtensionsStart != nil {try decoder.handleConflictingOneOf()}
@@ -590,6 +599,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       }()
       case 226: try {
         var v: Int32?
+        if case .b3(let _v) = self.oConflictExtensionsStart {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oConflictExtensionsStart != nil {try decoder.handleConflictingOneOf()}
@@ -598,6 +608,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       }()
       case 301: try {
         var v: Int32?
+        if case .a4(let _v) = self.oConflictExtensionsEnd {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oConflictExtensionsEnd != nil {try decoder.handleConflictingOneOf()}
@@ -606,6 +617,7 @@ extension SwiftProtoTesting_Order_OneofTraversalGeneration: SwiftProtobuf.Messag
       }()
       case 326: try {
         var v: Int32?
+        if case .b4(let _v) = self.oConflictExtensionsEnd {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.oConflictExtensionsEnd != nil {try decoder.handleConflictingOneOf()}
diff --git a/Tests/SwiftProtobufTests/unittest_swift_naming.pb.swift b/Tests/SwiftProtobufTests/unittest_swift_naming.pb.swift
index 64895f7ab..5f2348383 100644
--- a/Tests/SwiftProtobufTests/unittest_swift_naming.pb.swift
+++ b/Tests/SwiftProtobufTests/unittest_swift_naming.pb.swift
@@ -26901,6 +26901,7 @@ extension SwiftProtoTesting_Names_ValidIdentifiers: SwiftProtobuf.Message, Swift
       case 3: try { try decoder.decodeSingularInt32Field(value: &self.__3Field3) }()
       case 4: try {
         var v: Int32?
+        if case ._4(let _v) = self._2Of {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self._2Of != nil {try decoder.handleConflictingOneOf()}
@@ -26909,6 +26910,7 @@ extension SwiftProtoTesting_Names_ValidIdentifiers: SwiftProtobuf.Message, Swift
       }()
       case 5: try {
         var v: Int32?
+        if case ._5Field(let _v) = self._2Of {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self._2Of != nil {try decoder.handleConflictingOneOf()}
@@ -26986,6 +26988,7 @@ extension SwiftProtoTesting_Names_SpecialNames1: SwiftProtobuf.Message, SwiftPro
       switch fieldNumber {
       case 1: try {
         var v: String?
+        if case .str(let _v) = self.newValue {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.newValue != nil {try decoder.handleConflictingOneOf()}
@@ -27089,6 +27092,7 @@ extension SwiftProtoTesting_Names_SpecialNames3: SwiftProtobuf.Message, SwiftPro
         switch fieldNumber {
         case 1: try {
           var v: String?
+          if case .str(let _v) = _storage._newValue {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._newValue != nil {try decoder.handleConflictingOneOf()}
diff --git a/Tests/SwiftProtobufTests/unittest_swift_oneof_all_required.pb.swift b/Tests/SwiftProtobufTests/unittest_swift_oneof_all_required.pb.swift
index e0359e8c1..4f88a0b61 100644
--- a/Tests/SwiftProtobufTests/unittest_swift_oneof_all_required.pb.swift
+++ b/Tests/SwiftProtobufTests/unittest_swift_oneof_all_required.pb.swift
@@ -343,6 +343,7 @@ extension SwiftProtoTesting_OneOfContainer: SwiftProtobuf.Message, SwiftProtobuf
       }()
       case 6: try {
         var v: Int32?
+        if case .option4(let _v) = self.option {v = _v}
         try decoder.decodeSingularInt32Field(value: &v)
         if let v = v {
           if self.option != nil {try decoder.handleConflictingOneOf()}
diff --git a/Tests/SwiftProtobufTests/unittest_swift_oneof_merging.pb.swift b/Tests/SwiftProtobufTests/unittest_swift_oneof_merging.pb.swift
index 77599c68e..1a6473353 100644
--- a/Tests/SwiftProtobufTests/unittest_swift_oneof_merging.pb.swift
+++ b/Tests/SwiftProtobufTests/unittest_swift_oneof_merging.pb.swift
@@ -189,6 +189,7 @@ extension SwiftProtoTesting_Merging_TestMessage: SwiftProtobuf.Message, SwiftPro
       switch fieldNumber {
       case 111: try {
         var v: UInt32?
+        if case .oneofUint32(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularUInt32Field(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -210,6 +211,7 @@ extension SwiftProtoTesting_Merging_TestMessage: SwiftProtobuf.Message, SwiftPro
       }()
       case 113: try {
         var v: String?
+        if case .oneofString(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularStringField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
@@ -218,6 +220,7 @@ extension SwiftProtoTesting_Merging_TestMessage: SwiftProtobuf.Message, SwiftPro
       }()
       case 114: try {
         var v: Data?
+        if case .oneofBytes(let _v) = self.oneofField {v = _v}
         try decoder.decodeSingularBytesField(value: &v)
         if let v = v {
           if self.oneofField != nil {try decoder.handleConflictingOneOf()}
diff --git a/Tests/SwiftProtobufTests/unittest_swift_runtime_proto2.pb.swift b/Tests/SwiftProtobufTests/unittest_swift_runtime_proto2.pb.swift
index f6a7786ae..440266aee 100644
--- a/Tests/SwiftProtobufTests/unittest_swift_runtime_proto2.pb.swift
+++ b/Tests/SwiftProtobufTests/unittest_swift_runtime_proto2.pb.swift
@@ -1059,6 +1059,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         case 49: try { try decoder.decodeRepeatedEnumField(value: &_storage._repeatedEnum) }()
         case 51: try {
           var v: Int32?
+          if case .oneofInt32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1067,6 +1068,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 52: try {
           var v: Int64?
+          if case .oneofInt64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1075,6 +1077,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 53: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1083,6 +1086,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 54: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1091,6 +1095,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 55: try {
           var v: Int32?
+          if case .oneofSint32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1099,6 +1104,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 56: try {
           var v: Int64?
+          if case .oneofSint64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1107,6 +1113,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 57: try {
           var v: UInt32?
+          if case .oneofFixed32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFixed32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1115,6 +1122,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 58: try {
           var v: UInt64?
+          if case .oneofFixed64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFixed64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1123,6 +1131,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 59: try {
           var v: Int32?
+          if case .oneofSfixed32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSFixed32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1131,6 +1140,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 60: try {
           var v: Int64?
+          if case .oneofSfixed64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSFixed64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1139,6 +1149,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 61: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1147,6 +1158,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 62: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1155,6 +1167,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 63: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1163,6 +1176,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 64: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1171,6 +1185,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 65: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -1205,6 +1220,7 @@ extension SwiftProtoTesting_Message2: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 69: try {
           var v: SwiftProtoTesting_Message2.Enum?
+          if case .oneofEnum(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
diff --git a/Tests/SwiftProtobufTests/unittest_swift_runtime_proto3.pb.swift b/Tests/SwiftProtobufTests/unittest_swift_runtime_proto3.pb.swift
index 55e622b16..262bc6637 100644
--- a/Tests/SwiftProtobufTests/unittest_swift_runtime_proto3.pb.swift
+++ b/Tests/SwiftProtobufTests/unittest_swift_runtime_proto3.pb.swift
@@ -863,6 +863,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         case 49: try { try decoder.decodeRepeatedEnumField(value: &_storage._repeatedEnum) }()
         case 51: try {
           var v: Int32?
+          if case .oneofInt32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -871,6 +872,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 52: try {
           var v: Int64?
+          if case .oneofInt64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -879,6 +881,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 53: try {
           var v: UInt32?
+          if case .oneofUint32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularUInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -887,6 +890,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 54: try {
           var v: UInt64?
+          if case .oneofUint64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularUInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -895,6 +899,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 55: try {
           var v: Int32?
+          if case .oneofSint32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSInt32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -903,6 +908,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 56: try {
           var v: Int64?
+          if case .oneofSint64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSInt64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -911,6 +917,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 57: try {
           var v: UInt32?
+          if case .oneofFixed32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFixed32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -919,6 +926,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 58: try {
           var v: UInt64?
+          if case .oneofFixed64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFixed64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -927,6 +935,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 59: try {
           var v: Int32?
+          if case .oneofSfixed32(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSFixed32Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -935,6 +944,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 60: try {
           var v: Int64?
+          if case .oneofSfixed64(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularSFixed64Field(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -943,6 +953,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 61: try {
           var v: Float?
+          if case .oneofFloat(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularFloatField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -951,6 +962,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 62: try {
           var v: Double?
+          if case .oneofDouble(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularDoubleField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -959,6 +971,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 63: try {
           var v: Bool?
+          if case .oneofBool(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularBoolField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -967,6 +980,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 64: try {
           var v: String?
+          if case .oneofString(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularStringField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -975,6 +989,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 65: try {
           var v: Data?
+          if case .oneofBytes(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularBytesField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}
@@ -996,6 +1011,7 @@ extension SwiftProtoTesting_Message3: SwiftProtobuf.Message, SwiftProtobuf._Mess
         }()
         case 69: try {
           var v: SwiftProtoTesting_Message3.Enum?
+          if case .oneofEnum(let _v) = _storage._o {v = _v}
           try decoder.decodeSingularEnumField(value: &v)
           if let v = v {
             if _storage._o != nil {try decoder.handleConflictingOneOf()}

From 1eb44d228e311ea40934da03b80add752ed3fcda Mon Sep 17 00:00:00 2001
From: Pouya Yarandi <pouya.yarandi@divar.ir>
Date: Thu, 18 Apr 2024 23:57:04 +0330
Subject: [PATCH 3/4] Improve test code

---
 .../Test_OneodFields_Decoding.swift           | 48 +++++++++----------
 1 file changed, 24 insertions(+), 24 deletions(-)

diff --git a/Tests/SwiftProtobufTests/Test_OneodFields_Decoding.swift b/Tests/SwiftProtobufTests/Test_OneodFields_Decoding.swift
index 2b500b42c..b592e974b 100644
--- a/Tests/SwiftProtobufTests/Test_OneodFields_Decoding.swift
+++ b/Tests/SwiftProtobufTests/Test_OneodFields_Decoding.swift
@@ -18,55 +18,55 @@ import SwiftProtobuf
 
 final class Test_OneofFields_Decoding: XCTestCase {
   func testDecodeOneofCaptureField() throws {
-    var message = SwiftProtoTesting_Fuzz_Message()
+    var m = SwiftProtoTesting_Fuzz_Message()
 
-    message.oneofInt32 = 1
+    m.oneofInt32 = 1
     var d1 = PBTestDecoder(fieldNumber: 61)
-    try message.decodeMessage(decoder: &d1)
+    try m.decodeMessage(decoder: &d1)
     XCTAssertEqual(d1.value as? Int32, Int32(1))
 
-    message.oneofInt64 = 1
+    m.oneofInt64 = 1
     var d2 = PBTestDecoder(fieldNumber: 62)
-    try message.decodeMessage(decoder: &d2)
+    try m.decodeMessage(decoder: &d2)
     XCTAssertEqual(d2.value as? Int64, Int64(1))
 
-    message.oneofString = "message"
+    m.oneofString = "message"
     var d3 = PBTestDecoder(fieldNumber: 74)
-    try message.decodeMessage(decoder: &d3)
+    try m.decodeMessage(decoder: &d3)
     XCTAssertEqual(d3.value as? String, "message")
 
-    message.oneofBytes = "message".data(using: .utf8)!
+    m.oneofBytes = "message".data(using: .utf8)!
     var d4 = PBTestDecoder(fieldNumber: 75)
-    try message.decodeMessage(decoder: &d4)
+    try m.decodeMessage(decoder: &d4)
     XCTAssertEqual(d4.value as? Data, "message".data(using: .utf8)!)
 
-    message.oneofEnum = .two
+    m.oneofEnum = .two
     var d5 = PBTestDecoder(fieldNumber: 76)
-    try message.decodeMessage(decoder: &d5)
+    try m.decodeMessage(decoder: &d5)
     XCTAssertEqual(d5.value as? SwiftProtoTesting_Fuzz_AnEnum, .two)
   }
 
   func testDecodeOneofModifyField() throws {
-    var message = SwiftProtoTesting_Fuzz_Message()
+    var m = SwiftProtoTesting_Fuzz_Message()
 
-    var d1 = PBTestDecoder(fieldNumber: 61, decodingMode: .set(Int32(2)))
-    try message.decodeMessage(decoder: &d1)
-    XCTAssertEqual(message.oneofInt32, Int32(2))
+    var d1 = PBTestDecoder(fieldNumber: 61, decodingMode: .set(Int32(1)))
+    try m.decodeMessage(decoder: &d1)
+    XCTAssertEqual(m.oneofInt32, Int32(1))
 
-    var d2 = PBTestDecoder(fieldNumber: 62, decodingMode: .set(Int64(2)))
-    try message.decodeMessage(decoder: &d2)
-    XCTAssertEqual(message.oneofInt64, Int64(2))
+    var d2 = PBTestDecoder(fieldNumber: 62, decodingMode: .set(Int64(1)))
+    try m.decodeMessage(decoder: &d2)
+    XCTAssertEqual(m.oneofInt64, Int64(1))
 
     var d3 = PBTestDecoder(fieldNumber: 74, decodingMode: .set("message"))
-    try message.decodeMessage(decoder: &d3)
-    XCTAssertEqual(message.oneofString, "message")
+    try m.decodeMessage(decoder: &d3)
+    XCTAssertEqual(m.oneofString, "message")
 
     var d4 = PBTestDecoder(fieldNumber: 75, decodingMode: .set("message".data(using: .utf8)!))
-    try message.decodeMessage(decoder: &d4)
-    XCTAssertEqual(message.oneofBytes, "message".data(using: .utf8)!)
+    try m.decodeMessage(decoder: &d4)
+    XCTAssertEqual(m.oneofBytes, "message".data(using: .utf8)!)
 
     var d5 = PBTestDecoder(fieldNumber: 76, decodingMode: .set(SwiftProtoTesting_Fuzz_AnEnum.two))
-    try message.decodeMessage(decoder: &d5)
-    XCTAssertEqual(message.oneofEnum, .two)
+    try m.decodeMessage(decoder: &d5)
+    XCTAssertEqual(m.oneofEnum, .two)
   }
 }

From 924c2ea678ce569dce90dfb885711f9ec2f8760f Mon Sep 17 00:00:00 2001
From: Pouya Yarandi <pouya.yarandi@divar.ir>
Date: Fri, 19 Apr 2024 00:11:25 +0330
Subject: [PATCH 4/4] Fix test filename

---
 ...OneodFields_Decoding.swift => Test_OneofFields_Decoding.swift} | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 rename Tests/SwiftProtobufTests/{Test_OneodFields_Decoding.swift => Test_OneofFields_Decoding.swift} (100%)

diff --git a/Tests/SwiftProtobufTests/Test_OneodFields_Decoding.swift b/Tests/SwiftProtobufTests/Test_OneofFields_Decoding.swift
similarity index 100%
rename from Tests/SwiftProtobufTests/Test_OneodFields_Decoding.swift
rename to Tests/SwiftProtobufTests/Test_OneofFields_Decoding.swift