Merge pull request #28996 from nkcsgexi/ignore-originally-definedin-dwarf

ASTMangler: ignore original module name when DWARFMangling is enabled

Author: nkcsgexi

lib/AST/ASTMangler.cpp

@@ -499,6 +499,7 @@ std::string ASTMangler::mangleTypeAsUSR(Type Ty) {
 
 std::string ASTMangler::mangleDeclAsUSR(const ValueDecl *Decl,
                                         StringRef USRPrefix) {
+  DWARFMangling = true;
   beginManglingWithoutPrefix();
   llvm::SaveAndRestore<bool> allowUnnamedRAII(AllowNamelessEntities, true);
   Buffer << USRPrefix;
@@ -1790,7 +1791,12 @@ void ASTMangler::appendModule(const ModuleDecl *module,
     assert(useModuleName.empty());
     return appendOperator("SC");
   }
-  if (!useModuleName.empty())
+
+  // Enabling DWARFMangling indicate the mangled names are not part of the ABI,
+  // probably used by the debugger or IDE (USR). These mangled names will not be
+  // demangled successfully if we use the original module name instead of the
+  // actual module name.
+  if (!useModuleName.empty() && !DWARFMangling)
     appendIdentifier(useModuleName);
   else
     appendIdentifier(ModName);

test/IDE/reconstruct_type_from_mangled_name.swift

@@ -247,3 +247,9 @@ private
 func patatino<T: Comparable>(_ vers1: T, _ vers2: T) -> Bool {
   return vers1 < vers2;
 }
+
+@available(OSX 10.9, *)
+@_originallyDefinedIn(module: "OtherModule", OSX 10.13)
+public struct MovedHere {
+  public func foo() {}
+}