From ed7b27830d75b611c324307f21f1fe52f3f871de Mon Sep 17 00:00:00 2001
From: John McCall <rjmccall@apple.com>
Date: Fri, 6 Apr 2012 18:20:53 +0000
Subject: [PATCH] Fix a Sema invariant bug that I recently introduced involving
 the template instantiation of statement-expressions.

I think it was jyasskin who had a crashing testcase in this area;
hopefully this fixes it and he can find his testcase and check it in.

llvm-svn: 154189
---
 clang/lib/Sema/SemaExpr.cpp     |  3 +++
 clang/lib/Sema/TreeTransform.h  | 10 ++++++++--
 clang/test/CodeGenObjCXX/arc.mm | 11 +++++++++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 709b944447e0..82d23783f917 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -8567,6 +8567,9 @@ void Sema::ActOnStartStmtExpr() {
 }
 
 void Sema::ActOnStmtExprError() {
+  // Note that function is also called by TreeTransform when leaving a
+  // StmtExpr scope without rebuilding anything.
+
   DiscardCleanupsInEvaluationContext();
   PopExpressionEvaluationContext();
 }
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index f16b667a658d..fdb861eea51b 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -6736,14 +6736,20 @@ TreeTransform<Derived>::TransformAddrLabelExpr(AddrLabelExpr *E) {
 template<typename Derived>
 ExprResult 
 TreeTransform<Derived>::TransformStmtExpr(StmtExpr *E) {
+  SemaRef.ActOnStartStmtExpr();
   StmtResult SubStmt
     = getDerived().TransformCompoundStmt(E->getSubStmt(), true);
-  if (SubStmt.isInvalid())
+  if (SubStmt.isInvalid()) {
+    SemaRef.ActOnStmtExprError();
     return ExprError();
+  }
 
   if (!getDerived().AlwaysRebuild() &&
-      SubStmt.get() == E->getSubStmt())
+      SubStmt.get() == E->getSubStmt()) {
+    // Calling this an 'error' is unintuitive, but it does the right thing.
+    SemaRef.ActOnStmtExprError();
     return SemaRef.MaybeBindToTemporary(E);
+  }
 
   return getDerived().RebuildStmtExpr(E->getLParenLoc(),
                                       SubStmt.get(),
diff --git a/clang/test/CodeGenObjCXX/arc.mm b/clang/test/CodeGenObjCXX/arc.mm
index 7b7429085fbf..45211a2c19ab 100644
--- a/clang/test/CodeGenObjCXX/arc.mm
+++ b/clang/test/CodeGenObjCXX/arc.mm
@@ -241,3 +241,14 @@ Test37 *instantiate_init() {
 // CHECK: call i8* @objc_autoreleaseReturnValue
 template Test37* instantiate_init<int>();
 
+// Just make sure that the AST invariants hold properly here,
+// i.e. that we don't crash.
+// The block should get bound in the full-expression outside
+// the statement-expression.
+template <class T> class Test38 {
+  void test(T x) {
+    ^{ (void) x; }, ({ x; });
+  }
+};
+// CHECK: define weak_odr void @_ZN6Test38IiE4testEi(
+template class Test38<int>;