3 files changed, 16 insertions, 2 deletions
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 1e9f319d4f..cc94050a6f 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -8715,8 +8715,10 @@ void Sema::ActOnBlockArguments(Declarator &ParamInfo, Scope *CurScope) {
   // return type.  TODO:  what should we do with declarators like:
   //   ^ * { ... }
   // If the answer is "apply template argument deduction"....
-  if (RetTy != Context.DependentTy)
+  if (RetTy != Context.DependentTy) {
     CurBlock->ReturnType = RetTy;
+    CurBlock->TheDecl->setBlockMissingReturnType(false);
+  }
 
   // Push block parameters from the declarator if we had them.
   SmallVector<ParmVarDecl*, 8> Params;
diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index e8a61044b5..1255695016 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -1809,6 +1809,16 @@ Sema::ActOnBlockReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
   } else if (!RetValExp) {
     return StmtError(Diag(ReturnLoc, diag::err_block_return_missing_expr));
   } else if (!RetValExp->isTypeDependent()) {
+    if (CurBlock->TheDecl->blockMissingReturnType()) {
+      // when block's return type is not specified, all return types
+      // must strictly match.
+      if (Context.getCanonicalType(FnRetType) != 
+          Context.getCanonicalType(RetValExp->getType())) {
+          Diag(ReturnLoc, diag::err_typecheck_missing_return_type_incompatible) 
+            << RetValExp->getType() << FnRetType;
+          return StmtError();
+      }
+    }
     // we have a non-void block with an expression, continue checking
 
     // C99 6.8.6.4p3(136): The return statement is not an assignment. The
@@ -1820,7 +1830,7 @@ Sema::ActOnBlockReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
     NRVOCandidate = getCopyElisionCandidate(FnRetType, RetValExp, false);
     InitializedEntity Entity = InitializedEntity::InitializeResult(ReturnLoc,
                                                                    FnRetType,
-                                                           NRVOCandidate != 0);
+                                                          NRVOCandidate != 0);
     ExprResult Res = PerformMoveOrCopyInitialization(Entity, NRVOCandidate,
                                                      FnRetType, RetValExp);
     if (Res.isInvalid()) {
diff --git a/lib/Sema/TreeTransform.h b/lib/Sema/TreeTransform.h
index d7bdbafaba..3dc8136b78 100644
--- a/lib/Sema/TreeTransform.h
+++ b/lib/Sema/TreeTransform.h
@@ -8118,6 +8118,8 @@ TreeTransform<Derived>::TransformBlockExpr(BlockExpr *E) {
   // in above, CapturesCXXThis need be set here from the block
   // expression.
   blockScope->CapturesCXXThis = oldBlock->capturesCXXThis();
+  blockScope->TheDecl->setBlockMissingReturnType(
+                         oldBlock->blockMissingReturnType());
   
   SmallVector<ParmVarDecl*, 4> params;
   SmallVector<QualType, 4> paramTypes;