From 2cded44d82d7c6e9221419b7014a6d9053c69cf3 Mon Sep 17 00:00:00 2001
From: Hubert Tong <hubert.reinterpretcast@gmail.com>
Date: Tue, 1 Sep 2015 22:50:31 +0000
Subject: [PATCH] Fix assertion failure in TransformOpaqueValueExpr

Summary:
`OpaqueValueExpr`s may not have a source expression (as in the case when
they are created due to a default argument error).
This can cause an assertion failure in `TransformOpaqueValueExpr` during
template instantiation.

This patch fixes the assertion failure.

Reviewers: hfinkel, rsmith

Subscribers: fraggamuffin, cfe-commits

Differential Revision: http://reviews.llvm.org/D11582

Patch by Rachel Craik!

llvm-svn: 246600
---
 clang/lib/Sema/TreeTransform.h                | 2 +-
 clang/test/SemaTemplate/default-arguments.cpp | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 9074c39ad5db..692a2f1dcb48 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -7806,7 +7806,7 @@ TreeTransform<Derived>::TransformOffsetOfExpr(OffsetOfExpr *E) {
 template<typename Derived>
 ExprResult
 TreeTransform<Derived>::TransformOpaqueValueExpr(OpaqueValueExpr *E) {
-  assert(getDerived().AlreadyTransformed(E->getType()) &&
+  assert((!E->getSourceExpr() || getDerived().AlreadyTransformed(E->getType())) &&
          "opaque value expression requires transformation");
   return E;
 }
diff --git a/clang/test/SemaTemplate/default-arguments.cpp b/clang/test/SemaTemplate/default-arguments.cpp
index 0e972522d40b..37d144b71971 100644
--- a/clang/test/SemaTemplate/default-arguments.cpp
+++ b/clang/test/SemaTemplate/default-arguments.cpp
@@ -166,3 +166,9 @@ namespace NondefDecls {
   }
   template void f1<int>();  // expected-note{{in instantiation of function template specialization 'NondefDecls::f1<int>' requested here}}
 }
+
+template <typename T>
+struct C {
+  C(T t = ); // expected-error {{expected expression}}
+};
+C<int> obj;