3 files changed, 16 insertions, 6 deletions
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 05b3377b3e..06b72602fd 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -737,6 +737,8 @@ static void LangOptsToArgs(const LangOptions &Opts,
     Res.push_back("-ffake-address-space-map");
   if (Opts.ParseUnknownAnytype)
     Res.push_back("-funknown-anytype");
+  if (Opts.DebuggerSupport)
+    Res.push_back("-fdebugger-support");
   if (Opts.DelayedTemplateParsing)
     Res.push_back("-fdelayed-template-parsing");
   if (Opts.Deprecated)
@@ -1667,6 +1669,7 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   Opts.MRTD = Args.hasArg(OPT_mrtd);
   Opts.FakeAddressSpaceMap = Args.hasArg(OPT_ffake_address_space_map);
   Opts.ParseUnknownAnytype = Args.hasArg(OPT_funknown_anytype);
+  Opts.DebuggerSupport = Args.hasArg(OPT_fdebugger_support);
 
   // Record whether the __DEPRECATED define was requested.
   Opts.Deprecated = Args.hasFlag(OPT_fdeprecated_macro,
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index fa8721ce34..22185ed69e 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -9552,9 +9552,6 @@ ExprResult RebuildUnknownAnyExpr::VisitCallExpr(CallExpr *call) {
 }
 
 ExprResult RebuildUnknownAnyExpr::VisitObjCMessageExpr(ObjCMessageExpr *msg) {
-  ObjCMethodDecl *method = msg->getMethodDecl();
-  assert(method && "__unknown_anytype message without result type?");
-
   // Verify that this is a legal result type of a call.
   if (DestType->isArrayType() || DestType->isFunctionType()) {
     S.Diag(msg->getExprLoc(), diag::err_func_returning_array_function)
@@ -9562,8 +9559,11 @@ ExprResult RebuildUnknownAnyExpr::VisitObjCMessageExpr(ObjCMessageExpr *msg) {
     return ExprError();
   }
 
-  assert(method->getResultType() == S.Context.UnknownAnyTy);
-  method->setResultType(DestType);
+  // Rewrite the method result type if available.
+  if (ObjCMethodDecl *method = msg->getMethodDecl()) {
+    assert(method->getResultType() == S.Context.UnknownAnyTy);
+    method->setResultType(DestType);
+  }
 
   // Change the type of the message.
   msg->setType(DestType.getNonReferenceType());
diff --git a/lib/Sema/SemaExprObjC.cpp b/lib/Sema/SemaExprObjC.cpp
index 22953da97b..3df6d3f96e 100644
--- a/lib/Sema/SemaExprObjC.cpp
+++ b/lib/Sema/SemaExprObjC.cpp
@@ -355,7 +355,14 @@ bool Sema::CheckMessageArgumentTypes(QualType ReceiverType,
                               : diag::warn_inst_method_not_found;
     Diag(lbrac, DiagID)
       << Sel << isClassMessage << SourceRange(lbrac, rbrac);
-    ReturnType = Context.getObjCIdType();
+
+    // In debuggers, we want to use __unknown_anytype for these
+    // results so that clients can cast them.
+    if (getLangOptions().DebuggerSupport) {
+      ReturnType = Context.UnknownAnyTy;
+    } else {
+      ReturnType = Context.getObjCIdType();
+    }
     VK = VK_RValue;
     return false;
   }