From f4b911d3148dbdab54ab8ffec012db51b1f676f8 Mon Sep 17 00:00:00 2001
From: Gus Cairo <gus.cairo@apple.com>
Date: Wed, 3 May 2023 16:50:23 +0100
Subject: [PATCH] Return error if implementationOnlyImports is enabled with
 public visibility

---
 Sources/protoc-gen-swift/FileGenerator.swift | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Sources/protoc-gen-swift/FileGenerator.swift b/Sources/protoc-gen-swift/FileGenerator.swift
index 3aa749359..90fd06a69 100644
--- a/Sources/protoc-gen-swift/FileGenerator.swift
+++ b/Sources/protoc-gen-swift/FileGenerator.swift
@@ -91,6 +91,15 @@ class FileGenerator {
 
         p.print("import Foundation\n")
 
+        if self.generatorOptions.implementationOnlyImports,
+           self.generatorOptions.visibility == .public {
+            errorString = """
+                Cannot use @_implementationOnly imports when the proto visibility is public.
+                Either change the visibility to internal, or disable @_implementationOnly imports.
+            """
+            return
+        }
+
         // Import all other imports as @_implementationOnly if the visiblity is
         // internal and the option is set, to avoid exposing internal types to users.
         let visibilityAnnotation: String = {