AST: Fix opaque type mangling used by type reconstruction

Make sure we mangle opaque types using the same settings as the
debugger mangling (with OptimizeProtocolNames = false) to ensure
that we can reconstruct those names again.

Author: slavapestov

include/swift/AST/ASTMangler.h

@@ -236,6 +236,8 @@ class ASTMangler : public Mangler {
 
   std::string mangleLocalTypeDecl(const TypeDecl *type);
 
+  std::string mangleOpaqueTypeDecl(const OpaqueTypeDecl *decl);
+
   enum SpecialContext {
     ObjCContext,
     ClangImporterContext,

lib/AST/ASTMangler.cpp

@@ -29,6 +29,7 @@
 #include "swift/AST/ProtocolConformance.h"
 #include "swift/AST/ProtocolConformanceRef.h"
 #include "swift/Basic/Defer.h"
+#include "swift/Demangling/ManglingMacros.h"
 #include "swift/Demangling/ManglingUtils.h"
 #include "swift/Demangling/Demangler.h"
 #include "swift/Strings.h"
@@ -691,6 +692,12 @@ std::string ASTMangler::mangleLocalTypeDecl(const TypeDecl *type) {
   return finalize();
 }
 
+std::string ASTMangler::mangleOpaqueTypeDecl(const OpaqueTypeDecl *decl) {
+  DWARFMangling = true;
+  OptimizeProtocolNames = false;
+  return mangleDeclAsUSR(decl->getNamingDecl(), MANGLING_PREFIX_STR);
+}
+
 void ASTMangler::appendSymbolKind(SymbolKind SKind) {
   switch (SKind) {
     case SymbolKind::Default: return;

lib/AST/Decl.cpp

@@ -7088,7 +7088,7 @@ Identifier OpaqueTypeDecl::getOpaqueReturnTypeIdentifier() const {
   {
     llvm::raw_svector_ostream os(mangleBuf);
     Mangle::ASTMangler mangler;
-    os << mangler.mangleDeclAsUSR(getNamingDecl(), MANGLING_PREFIX_STR);
+    os << mangler.mangleOpaqueTypeDecl(this);
   }
 
   OpaqueReturnTypeIdentifier = getASTContext().getIdentifier(mangleBuf);

lib/Serialization/ModuleFormat.h

@@ -55,7 +55,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 552; // simple didSet
+const uint16_t SWIFTMODULE_VERSION_MINOR = 553; // change to USR mangling
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///

lib/Serialization/Serialization.cpp

@@ -5067,8 +5067,7 @@ void Serializer::writeAST(ModuleOrSourceFile DC) {
     for (auto OTD : opaqueReturnTypeDecls) {
       hasOpaqueReturnTypes = true;
       Mangle::ASTMangler Mangler;
-      auto MangledName = Mangler.mangleDeclAsUSR(OTD->getNamingDecl(),
-                                                 MANGLING_PREFIX_STR);
+      auto MangledName = Mangler.mangleOpaqueTypeDecl(OTD);
       opaqueReturnTypeGenerator.insert(MangledName, addDeclRef(OTD));
     }
   }

test/DebugInfo/opaque_result_type.swift

@@ -0,0 +1,15 @@
+// RUN: %target-swift-frontend -emit-ir -g %s -disable-availability-checking
+
+public protocol P {
+  associatedtype Horse
+}
+
+public protocol Feed {}
+
+public struct Hay : Feed {}
+
+public func hasOpaqueResult<T : P>(_: T.Type, _: T.Horse) -> some Feed {
+  return Hay()
+}
+
+