[analyzer] Don't warn for returning void expressions in void blocks.

This was slightly tricky because BlockDecls don't currently store an
inferred return type. However, we can rely on the fact that blocks with
inferred return types will have return statements that match the inferred
type.

<rdar://problem/13665798>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179699 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 24 insertions, 3 deletions

diff --git a/lib/StaticAnalyzer/Checkers/ReturnUndefChecker.cpp b/lib/StaticAnalyzer/Checkers/ReturnUndefChecker.cpp
index 7a5d993601..ed96c401a7 100644
--- a/lib/StaticAnalyzer/Checkers/ReturnUndefChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/ReturnUndefChecker.cpp
@@ -55,8 +55,17 @@ void ReturnUndefChecker::checkPreStmt(const ReturnStmt *RS,
     //   void test() {
     //     return foo();
     //   }
-    if (RT.isNull() || !RT->isVoidType())
-      emitUndef(C, RetE);
+    if (!RT.isNull() && RT->isVoidType())
+      return;
+
+    // Not all blocks have explicitly-specified return types; if the return type
+    // is not available, but the return value expression has 'void' type, assume
+    // Sema already checked it.
+    if (RT.isNull() && isa<BlockDecl>(SFC->getDecl()) &&
+        RetE->getType()->isVoidType())
+      return;
+
+    emitUndef(C, RetE);
     return;
   }
 
diff --git a/lib/StaticAnalyzer/Core/CallEvent.cpp b/lib/StaticAnalyzer/Core/CallEvent.cpp
index 45b2e219d9..dfd20b8b33 100644
--- a/lib/StaticAnalyzer/Core/CallEvent.cpp
+++ b/lib/StaticAnalyzer/Core/CallEvent.cpp
@@ -239,8 +239,20 @@ QualType CallEvent::getDeclaredResultType(const Decl *D) {
   assert(D);
   if (const FunctionDecl* FD = dyn_cast<FunctionDecl>(D))
     return FD->getResultType();
-  else if (const ObjCMethodDecl* MD = dyn_cast<ObjCMethodDecl>(D))
+  if (const ObjCMethodDecl* MD = dyn_cast<ObjCMethodDecl>(D))
     return MD->getResultType();
+  if (const BlockDecl *BD = dyn_cast<BlockDecl>(D)) {
+    // Blocks are difficult because the return type may not be stored in the
+    // BlockDecl itself. The AST should probably be enhanced, but for now we
+    // just do what we can.
+    QualType Ty = BD->getSignatureAsWritten()->getType();
+    if (const FunctionType *FT = Ty->getAs<FunctionType>())
+      if (!FT->getResultType()->isDependentType())
+        return FT->getResultType();
+
+    return QualType();
+  }
+  
   return QualType();
 }