From 71d0a67297da743a5c0c4af877281dc2b28ed020 Mon Sep 17 00:00:00 2001
From: Slava Pestov <spestov@apple.com>
Date: Sun, 10 Feb 2019 23:57:35 -0500
Subject: [PATCH 1/2] RemoteAST: Fix error existential introspection on Linux

---
 include/swift/Remote/MetadataReader.h | 31 ++++++++++++---------------
 test/RemoteAST/existentials.swift     |  2 --
 2 files changed, 14 insertions(+), 19 deletions(-)

diff --git a/include/swift/Remote/MetadataReader.h b/include/swift/Remote/MetadataReader.h
index 3ad61c68ab2ed..2a6eb93afb40b 100644
--- a/include/swift/Remote/MetadataReader.h
+++ b/include/swift/Remote/MetadataReader.h
@@ -361,24 +361,21 @@ class MetadataReader {
     bool isObjC = false;
     bool isBridged = false;
 
-    // If we can determine the Objective-C class name, this is probably an
-    // error existential with NSError-compatible layout.
-    std::string ObjCClassName;
-    if (readObjCClassName(*MetadataAddress, ObjCClassName)) {
-      if (ObjCClassName == "__SwiftNativeNSError")
-        isObjC = true;
-      else
+    auto Meta = readMetadata(*MetadataAddress);
+    if (auto ClassMeta = dyn_cast<TargetClassMetadata<Runtime>>(Meta)) {
+      if (ClassMeta->isPureObjC()) {
+        // If we can determine the Objective-C class name, this is probably an
+        // error existential with NSError-compatible layout.
+        std::string ObjCClassName;
+        if (readObjCClassName(*MetadataAddress, ObjCClassName)) {
+          if (ObjCClassName == "__SwiftNativeNSError")
+            isObjC = true;
+          else
+            isBridged = true;
+        }
+      } else {
         isBridged = true;
-    } else {
-      // Otherwise, we can check to see if this is a class metadata with the
-      // kind value's least significant bit set, which indicates a pure
-      // Swift class.
-      auto Meta = readMetadata(*MetadataAddress);
-      auto ClassMeta = dyn_cast<TargetClassMetadata<Runtime>>(Meta);
-      if (!ClassMeta)
-        return None;
-
-      isObjC = ClassMeta->isPureObjC();
+      }
     }
 
     if (isBridged) {
diff --git a/test/RemoteAST/existentials.swift b/test/RemoteAST/existentials.swift
index 6dc7508a0132d..86cc93574eb0b 100644
--- a/test/RemoteAST/existentials.swift
+++ b/test/RemoteAST/existentials.swift
@@ -1,5 +1,3 @@
-// UNSUPPORTED: linux
-// <rdar://problem/42793848>
 // RUN: %target-swift-remoteast-test %s | %FileCheck %s
 
 // REQUIRES: swift-remoteast-test

From c20d085bde56d0933e11a1dc9dec3307a9d2f123 Mon Sep 17 00:00:00 2001
From: Slava Pestov <spestov@apple.com>
Date: Thu, 28 Feb 2019 00:00:35 -0500
Subject: [PATCH 2/2] RemoteAST: Fix Error existential introspection on Linux

We don't have tests that look at the instance address
on the Swift side, but lldb is going to use this API
shortly.
---
 include/swift/Remote/MetadataReader.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/swift/Remote/MetadataReader.h b/include/swift/Remote/MetadataReader.h
index 2a6eb93afb40b..976a560b1c430 100644
--- a/include/swift/Remote/MetadataReader.h
+++ b/include/swift/Remote/MetadataReader.h
@@ -410,11 +410,15 @@ class MetadataReader {
     StoredPointer InstanceAddress =
         InstanceMetadataAddressAddress + 2 * sizeof(StoredPointer);
 
+    // When built with Objective-C interop, the runtime also stores a conformance
+    // to Hashable and the base type introducing the Hashable conformance.
+    if (isObjC)
+      InstanceAddress += 2 * sizeof(StoredPointer);
+
     // Round up to alignment, and we have the start address of the
     // instance payload.
     auto AlignmentMask = VWT->getAlignmentMask();
-    auto Offset = (sizeof(HeapObject) + AlignmentMask) & ~AlignmentMask;
-    InstanceAddress += Offset;
+    InstanceAddress = (InstanceAddress + AlignmentMask) & ~AlignmentMask;
 
     return RemoteExistential(
         RemoteAddress(*InstanceMetadataAddress),