[Bug c++/113274] New: Memoization in template parameters is overly aggressive; false memoization for const pointers

["janschultke at googlemail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113274

            Bug ID: 113274
           Summary: Memoization in template parameters is overly
                    aggressive; false memoization for const pointers
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: janschultke at googlemail dot com
  Target Milestone: ---

## Minimal Reproducible Example (https://godbolt.org/z/Y7Kr9o546)

template <auto>
struct A {
    static constexpr bool value = false;
};

template <auto p>
  requires __is_same(decltype(p), int*)
struct A<p> {
    static constexpr bool value = false;
};

int x = 0;
//static_assert( A<&x>::value );
static_assert( A<const_cast<const int*>(&x)>::value == false );

## Explanation

Uncommenting the first static_assert causes compilation failure of the second
static_assert.
This should definitely not happen, as the following instantiations should be
distinct:

- A<(int*) &x>
- A<(const int*) &x>

GCC aggressively memoizes the first instantiation in A<&x>, which results in
the subsequent A<(const int*)&x>::value being identical, even though it should
not be.