Clang++ fails to match template template parameters as function arguments

[PiliLatiesa]

Clang++ trunk started rejecting the following testcase (adapted from https://eel.is/c++draft/temp#arg.template-example-3). Clang 19 accepts it. It's a recent regression.

template <template <class, class...> class TT, class T1, class... Rest>
void f(TT<T1, Rest...> const &) {}

template <typename T1> struct A {};

int main()
{ 
  A<int> a;
  f(a);   // bogus "no matching function for call to 'f'"
}

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (PiliLatiesa)

Clang++ trunk started rejecting the following testcase (adapted from https://eel.is/c++draft/temp#arg.template-example-3). Clang 19 accepts it. It's a recent regression.

template <template <class, class...> class TT, class T1, class... Rest>
void f(TT<T1, Rest...> const &) {}

template <typename T1> struct A {};

int main()
{ 
  A<int> a;
  f(a);   // bogus "no matching function for call to 'f'"
}

[zyn0217]

@mizvekov Is it also related to #96023?

[cor3ntin]

Yes #96023 (comment)

[mizvekov]

This will be fixed by #111457