A type-transforming builtin in a friend template's requires-clause is lost when the enclosing class template is instantiated

[jonatanlinden]

Issue Summary

A friend function template defined in a class template, whose requires-clause applies a type-transforming builtin such as __remove_cvref(T) to the friend's own template parameter, never sees the builtin applied. When the function is called with an lvalue, T is deduced as a reference type, the constraint is evaluated with the reference still on, __is_base_of is false, and no candidate matches. The code is rejected with "error: no operator "!" matches these operands".
With an rvalue operand the code is accepted.

Reproducing Source Code

template <class> struct C {
  template <typename T>
  requires __is_base_of(C, __remove_cvref(T))
  friend int operator!(T &&) { return 0; }
};
struct D : C<int> {} d;
int x = !d;

Command-line Options

cpfe --c++20 --no_code_gen repro.cpp

Type of Issue

[Front End] This code SHOULD compile with these options.

Additional Details

Also doesn't compile with:

cpfe --c++20 --clang --clang_version=180000 --no_code_gen repro.cpp
cpfe --c++20 --g++ --gnu_version=130000 --no_code_gen repro.cpp

clang and GCC both accept the code. https://godbolt.org/z/EcE5fG6ET

The pattern comes from libc++'s __range_adaptor_closure, so arr | std::views::reverse fails to compile with EDG.

The full diagnostic produced is:

"repro.cpp", line 10: error: no operator "!" matches these operands
            operand types are: ! D
  int x = !d;   // T deduced as D& from the lvalue; __remove_cvref(D&) is D
          ^
"repro.cpp", line 7: note: substituting "<D &>" for function template "operator!" failed constraints
    friend int operator!(T &&) { return 0; }
               ^
Note: atomic constraint evaluates to false

Reproducing (Standard) Configuration(s)

linux-gcc-debug

Reproducing (Non-standard) Configuration

No response

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