clang/test/SemaTemplate/pr52970.cpp

   1 // RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify %s
   2 // RUN: %clang_cc1 -fsyntax-only -std=c++14 -verify %s
   3 // RUN: %clang_cc1 -fsyntax-only -std=c++17 -verify %s
   4 // RUN: %clang_cc1 -fsyntax-only -std=c++20 -verify=cxx20 %s
   5 // expected-no-diagnostics
   6
   7 struct Incomplete;
   8 template <class T> struct Holder { T t; };
   9
  10 namespace DotFollowingFunctionName {
  11 struct Good {
  12   struct Nested {
  13     int b;
  14   } a;
  15 };
  16
  17 struct Bad {
  18   Holder<Incomplete> a();
  19 };
  20
  21 template <class T>
  22 constexpr auto f(T t) -> decltype((t.a.b, true)) { return true; }
  23 constexpr bool f(...) { return false; }
  24
  25 static_assert(DotFollowingFunctionName::f(Good{}), "");
  26 static_assert(!DotFollowingFunctionName::f(Bad{}), "");
  27
  28 #if __cplusplus >= 202002L
  29 template <class T>
  30 concept C = requires(T t) { t.a.b; };
  31   // cxx20-note@-1 {{because 't.a.b' would be invalid: reference to non-static member function must be called}}
  32
  33 static_assert(C<Good>);
  34 static_assert(!C<Bad>);
  35 static_assert(C<Bad>); // cxx20-error {{static assertion failed}}
  36   // cxx20-note@-1 {{because 'Bad' does not satisfy 'C'}}
  37 #endif
  38 } // namespace DotFollowingFunctionName
  39
  40 namespace DotFollowingPointer {
  41 struct Good {
  42   int begin();
  43 };
  44 using Bad = Holder<Incomplete> *;
  45
  46 template <class T>
  47 constexpr auto f(T t) -> decltype((t.begin(), true)) { return true; }
  48 constexpr bool f(...) { return false; }
  49
  50 static_assert(DotFollowingPointer::f(Good{}), "");
  51 static_assert(!DotFollowingPointer::f(Bad{}), "");
  52
  53 #if __cplusplus >= 202002L
  54 template <class T>
  55 concept C = requires(T t) { t.begin(); };
  56   // cxx20-note@-1 {{because 't.begin()' would be invalid: member reference type 'Holder<Incomplete> *' is a pointer}}
  57
  58 static_assert(C<Good>);
  59 static_assert(!C<Bad>);
  60 static_assert(C<Bad>); // cxx20-error {{static assertion failed}}
  61   // cxx20-note@-1 {{because 'Bad' (aka 'Holder<Incomplete> *') does not satisfy 'C'}}
  62 #endif
  63 } // namespace DotFollowingPointer