CWG3003: Naming a deducible template for class template argument deduction

[Endilll]

Clang crashes on the following code (https://godbolt.org/z/KcoqrEME7) since 19.1.0:

template <typename T> struct A { A(T); };

template <typename T, template <typename> class TT = A>
using Alias = TT<T>;

template <typename T>
using Alias2 = Alias<T>;

void h() { Alias2 a(42); }
void h2() { Alias a(42); }

From cplusplus/CWG#670, https://cplusplus.github.io/CWG/issues/3003.html.

[llvmbot]

@llvm/issue-subscribers-c-17

Author: Vlad Serebrennikov (Endilll)

Clang crashes on the following code (https://godbolt.org/z/KcoqrEME7) since 19.1.0: ```cpp template <typename T> struct A { A(T); };

template <typename T, template <typename> class TT = A>
using Alias = TT<T>;

template <typename T>
using Alias2 = Alias<T>;

void h() { Alias2 a(42); }
void h2() { Alias a(42); }

From https://github.com/cplusplus/CWG/issues/670, https://cplusplus.github.io/CWG/issues/3003.html.
</details>

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Vlad Serebrennikov (Endilll)

Clang crashes on the following code (https://godbolt.org/z/KcoqrEME7) since 19.1.0: ```cpp template <typename T> struct A { A(T); };

template <typename T, template <typename> class TT = A>
using Alias = TT<T>;

template <typename T>
using Alias2 = Alias<T>;

void h() { Alias2 a(42); }
void h2() { Alias a(42); }

From https://github.com/cplusplus/CWG/issues/670, https://cplusplus.github.io/CWG/issues/3003.html.
</details>

[cor3ntin]

@mizvekov