clang/test/SemaTemplate/cxx2a-constraint-exprs.cpp

   1 // RUN:  %clang_cc1 -std=c++2a -verify %s
   2
   3 // Make sure constraint expressions are unevaluated before being substituted
   4 // into during satisfaction checking.
   5
   6 template<typename T> constexpr bool f = T::value;
   7 // expected-error@-1 4{{type}}
   8
   9 namespace unevaluated {
  10   template<typename T> concept Foo = false && f<int>;
  11   bool k = Foo<int>;
  12   template<typename T> requires false && f<int> struct S {};
  13   // expected-note@-1{{because}}
  14   using s = S<int>; // expected-error {{constraints not satisfied}}
  15   template<typename T> void foo() requires false && f<int> { };
  16   // expected-note@-1{{because}} expected-note@-1{{candidate template ignored}}
  17   int a = (foo<int>(), 0); // expected-error{{no matching function}}
  18   template<typename T> void bar() requires requires { requires false && f<int>; } { };
  19   // expected-note@-1{{because}} expected-note@-1{{candidate template ignored}}
  20   int b = (bar<int>(), 0); // expected-error{{no matching function}}
  21   template<typename T> struct M { static void foo() requires false && f<int> { }; };
  22   // expected-note@-1{{because}}
  23   int c = (M<int>::foo(), 0);
  24   // expected-error@-1{{invalid reference to function 'foo': constraints not satisfied}}
  25 }
  26
  27 namespace constant_evaluated {
  28   template<typename T> requires f<int[0]> struct S {};
  29   // expected-note@-1{{in instantiation of}} expected-note@-1{{while substituting}}
  30   using s = S<int>;
  31   // expected-note@-1 {{while checking}}
  32   template<typename T> void foo() requires f<int[1]> { };
  33   // expected-note@-1{{in instantiation}} expected-note@-1{{while substituting}} \
  34      expected-note@-1{{candidate template ignored}}
  35   int a = (foo<int>(), 0);
  36   // expected-note@-1 {{while checking}} expected-error@-1{{no matching function}} \
  37      expected-note@-1 {{in instantiation}}
  38   template<typename T> void bar() requires requires { requires f<int[2]>; } { };
  39   // expected-note@-1{{in instantiation}} \
  40      expected-note@-1{{while substituting}} \
  41      expected-note@-1 {{while checking the satisfaction of nested requirement}}
  42   int b = (bar<int>(), 0);
  43   template<typename T> struct M { static void foo() requires f<int[3]> { }; };
  44   // expected-note@-1{{in instantiation}} expected-note@-1{{while substituting}}
  45   int c = (M<int>::foo(), 0);
  46   // expected-note@-1 {{while checking}}
  47 }