This patch emits a more appropriate (but still noisy) diagnostic stream when a lambda-expression is encountered within a non-type default argument.
For e.g. template<int N = ([] { return 5; }())> int f();
As opposed to complaining that a lambda expression is not allowed in an unevaluated operand, the patch complains about the lambda being forbidden in a constant expression context (which will be allowed in C++17 now that they have been accepted by EWG, unless of course CWG or national bodies (that have so far shown no signs of concern) rise in protest)
As I start submitting patches for constexpr lambdas (http://wg21.link/P0170R0) under C++1z (OK'd by Richard Smith at Kona), this will be one less change to make.
Thanks!
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@253431
91177308-0d34-0410-b5e6-
96231b3b80d8
// end of the template-parameter-list rather than a greater-than
// operator.
GreaterThanIsOperatorScope G(GreaterThanIsOperator, false);
- EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated);
+ EnterExpressionEvaluationContext Unevaluated(Actions,
+ Sema::ConstantEvaluated);
DefaultArg = Actions.CorrectDelayedTyposInExpr(ParseAssignmentExpression());
if (DefaultArg.isInvalid())
// RUN: %clang_cc1 -fsyntax-only -verify -triple=x86_64-linux-gnu %s
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify -triple=x86_64-linux-gnu %s -DCPP11ONLY
// C++11 [temp.arg.nontype]p1:
//
// be one of:
// -- an integral constant expression; or
// -- the name of a non-type template-parameter ; or
+#ifndef CPP11ONLY
+
namespace non_type_tmpl_param {
template <int N> struct X0 { X0(); };
template <int N> X0<N>::X0() { }
int* iptr = &i;
X0<iptr> x0b; // expected-error{{non-type template argument for template parameter of pointer type 'int *' must have its address taken}}
}
+#endif // CPP11ONLY
+
+namespace default_args {
+#ifdef CPP11ONLY
+namespace lambdas {
+template<int I = ([] { return 5; }())> //expected-error 2{{constant expression}} expected-note{{constant expression}}
+int f();
+}
+#endif // CPP11ONLY
+
+}
\ No newline at end of file