Ensure we enter an unevaluated context when instantiating a noexcept

expression. Fixes bug raised by hhinnant to cfe-dev

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@132350 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Sema/TreeTransform.h

@@ -7516,6 +7516,7 @@ TreeTransform<Derived>::TransformUnresolvedMemberExpr(UnresolvedMemberExpr *Old)
 template<typename Derived>
 ExprResult
 TreeTransform<Derived>::TransformCXXNoexceptExpr(CXXNoexceptExpr *E) {
+  EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated);
   ExprResult SubExpr = getDerived().TransformExpr(E->getOperand());
   if (SubExpr.isInvalid())
     return ExprError();

test/SemaCXX/dependent-noexcept-unevaluated.cpp

@@ -0,0 +1,41 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++0x %s
+
+template <class T>
+T&&
+declval() noexcept;
+
+template <class T>
+struct some_trait
+{
+    static const bool value = false;
+};
+
+template <class T>
+void swap(T& x, T& y) noexcept(some_trait<T>::value)
+{
+    T tmp(static_cast<T&&>(x));
+    x = static_cast<T&&>(y);
+    y = static_cast<T&&>(tmp);
+}
+
+template <class T, unsigned N>
+struct array
+{
+    T data[N];
+
+    void swap(array& a) noexcept(noexcept(swap(declval<T&>(), declval<T&>())));
+};
+
+struct DefaultOnly
+{
+    DefaultOnly() = default;
+    DefaultOnly(const DefaultOnly&) = delete;
+    DefaultOnly& operator=(const DefaultOnly&) = delete;
+    ~DefaultOnly() = default;
+};
+
+int main()
+{
+    array<DefaultOnly, 1> a, b;
+}
+