1 // RUN: %clang_cc1 -std=c++2a -verify %s
2 
3 // When forming and checking satisfaction of atomic constraints, we will
4 // substitute still-dependent template arguments into an expression, and later
5 // substitute into the result. This creates some unique situations; check that
6 // they work.
7 
8 namespace SubstIntoResolvedTypeTemplateArg {
9   template<int, class> struct X {};
10 
11   template<class T> concept A = true;
12   template<class T> concept B = sizeof(T) != 0;
13   template<class T> concept C = B<X<1, T>>;
14 
15   int f(A auto); // expected-note {{candidate}}
16   int f(C auto); // expected-note {{candidate}}
17   int k1 = f(0); // expected-error {{ambiguous}}
18 
19   template<class T> concept D = A<T> && B<X<1, T>>;
20   int f(D auto);
21   int k2 = f(0); // ok
22 
23   // The atomic constraint formed from B<X<(int)'\1', T>> is identical to the
24   // one formed from C, even though the template arguments are written as
25   // different expressions; the "equivalent" rules are used rather than the
26   // "identical" rules when matching template arguments in concept-ids.
27   template<class T> concept E = A<T> && B<X<(int)'\1', T>>;
28   int g(C auto);
29   int g(E auto); // expected-note {{candidate}}
30   int k3 = g(0);
31 
32   int g(D auto); // expected-note {{candidate}}
33   int k4 = g(0); // expected-error {{ambiguous}}
34 }
35