[Concepts] Parsing of requires-clause in template-declaration

Summary:
This change implements parse-only acceptance of the optional
requires-clause in a template-declaration. Diagnostic testing is added
for cases where the grammar is ambiguous with the expectation that the
longest token sequence which matches the syntax of a
constraint-expression is consumed without backtracking.

Reviewers: faisalv, fraggamuffin, rsmith

Reviewed By: rsmith

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D10462

llvm-svn: 240611

1 files changed, 82 insertions, 0 deletions

diff --git a/clang/test/Parser/cxx-concepts-requires-clause.cpp b/clang/test/Parser/cxx-concepts-requires-clause.cpp
new file mode 100644
index 00000000000..01893a94cbc
--- /dev/null
+++ b/clang/test/Parser/cxx-concepts-requires-clause.cpp
@@ -0,0 +1,82 @@
+// RUN: %clang_cc1 -std=c++14 -fconcepts-ts -x c++ %s -verify
+// expected-no-diagnostics
+
+// Test parsing of the optional requires-clause in a template-declaration.
+
+template <typename T> requires true
+void foo() { }
+
+
+template <typename T> requires !0
+struct A {
+  void foo();
+  struct AA;
+  enum E : int;
+  static int x;
+
+  template <typename> requires true
+  void Mfoo();
+
+  template <typename> requires true
+  struct M;
+
+  template <typename> requires true
+  static int Mx;
+
+  template <typename TT> requires true
+  using MQ = M<TT>;
+};
+
+template <typename T> requires !0
+void A<T>::foo() { }
+
+template <typename T> requires !0
+struct A<T>::AA { };
+
+template <typename T> requires !0
+enum A<T>::E : int { E0 };
+
+template <typename T> requires !0
+int A<T>::x = 0;
+
+template <typename T> requires !0
+template <typename> requires true
+void A<T>::Mfoo() { }
+
+template <typename T> requires !0
+template <typename> requires true
+struct A<T>::M { };
+
+template <typename T> requires !0
+template <typename> requires true
+int A<T>::Mx = 0;
+
+
+template <typename T> requires true
+int x = 0;
+
+template <typename T> requires true
+using Q = A<T>;
+
+struct C {
+  template <typename> requires true
+  void Mfoo();
+
+  template <typename> requires true
+  struct M;
+
+  template <typename> requires true
+  static int Mx;
+
+  template <typename T> requires true
+  using MQ = M<T>;
+};
+
+template <typename> requires true
+void C::Mfoo() { }
+
+template <typename> requires true
+struct C::M { };
+
+template <typename> requires true
+int C::Mx = 0;