From bbbc3467682be89adaffbcbb855f6253dec5fe34 Mon Sep 17 00:00:00 2001
From: Doug Gregor <dgregor@apple.com>
Date: Sun, 27 Nov 2022 11:47:25 -0800
Subject: [PATCH] [Macros] Treat MacroDecl as a local context, like functions
 are.

---
 include/swift/AST/DeclContext.h     | 6 +++---
 lib/AST/ASTMangler.cpp              | 2 +-
 lib/Serialization/Serialization.cpp | 3 ++-
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/swift/AST/DeclContext.h b/include/swift/AST/DeclContext.h
index 4bc2a3a7430..c31daf43d9d 100644
--- a/include/swift/AST/DeclContext.h
+++ b/include/swift/AST/DeclContext.h
@@ -94,14 +94,14 @@ enum class DeclContextKind : unsigned {
   EnumElementDecl,
   AbstractFunctionDecl,
   SerializedLocal,
-  Last_LocalDeclContextKind = SerializedLocal,
+  MacroDecl,
+  Last_LocalDeclContextKind = MacroDecl,
 
   Module,
   FileUnit,
   GenericTypeDecl,
   ExtensionDecl,
-  MacroDecl,
-  Last_DeclContextKind = MacroDecl
+  Last_DeclContextKind = ExtensionDecl
 };
 
 /// Kinds of DeclContexts after deserialization.
diff --git a/lib/AST/ASTMangler.cpp b/lib/AST/ASTMangler.cpp
index 17a6a303150..233dac6d9b3 100644
--- a/lib/AST/ASTMangler.cpp
+++ b/lib/AST/ASTMangler.cpp
@@ -2381,7 +2381,7 @@ void ASTMangler::appendContext(const DeclContext *ctx, StringRef useModuleName)
     return appendContext(ctx->getParent(), useModuleName);
 
   case DeclContextKind::MacroDecl:
-    llvm_unreachable("macro declarations are never mangled");
+    return appendContext(ctx->getParent(), useModuleName);
   }
 
   llvm_unreachable("bad decl context");
diff --git a/lib/Serialization/Serialization.cpp b/lib/Serialization/Serialization.cpp
index b661bb70801..1bb70db035d 100644
--- a/lib/Serialization/Serialization.cpp
+++ b/lib/Serialization/Serialization.cpp
@@ -485,7 +485,8 @@ static ModuleDecl *getModule(ModuleOrSourceFile DC) {
 
 static bool shouldSerializeAsLocalContext(const DeclContext *DC) {
   return DC->isLocalContext() && !isa<AbstractFunctionDecl>(DC) &&
-        !isa<SubscriptDecl>(DC) && !isa<EnumElementDecl>(DC);
+        !isa<SubscriptDecl>(DC) && !isa<EnumElementDecl>(DC) &&
+        !isa<MacroDecl>(DC);
 }
 
 namespace {