Syntax error for overloaded operator[] in 32-bit address space

[ararmine]

x86-64 clang 19.1.0 issues a compilation error for the following example:

1. cat ex.cpp

struct value {
      public:
        operator int() const;
        struct value &operator[](const char * __ptr32 _param_1);
};

extern struct value *new_value();

int json_send_error(int status)
{
  struct value * v = new_value();
  (void)(*v)["error"];
  return 0;
}

2. clang ex.cpp -fms-extensions -S

ex.cpp:13:13: error: use of overloaded operator '[]' is ambiguous (with operand types 'struct value' and 'const char[6]')
   13 |   (void)(*v)["error"];
      |         ~~~~^~~~~~~~
ex.cpp:5:23: note: candidate function
    5 |         struct value &operator[](const char * __ptr32 _param_1);
      |                       ^
ex.cpp:13:13: note: built-in candidate operator[](long, const char *)
   13 |   (void)(*v)["error"];
      |             ^
1 error generated.

https://godbolt.org/z/dbvEGfz13

x64 MSVC v.19 compiles successfully https://godbolt.org/z/qWc584f5f

[ararmine]

In SemaOverload.cpp there is a function:

/// Helper function for adjusting address spaces for the pointer or reference
/// operands of builtin operators depending on the argument.
static QualType AdjustAddressSpaceForBuiltinOperandType(Sema &S, QualType T,
                                                        Expr *Arg) {
  return S.Context.getAddrSpaceQualType(T, Arg->getType().getAddressSpace());
}

which is called when creating built-in assignment operators. I tried to call it also when creating built-in operator[] and it worked.
Could this be an acceptable solution?

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (ararmine)

**x86-64 clang 19.1.0** issues a compilation error for the following example: 1. cat ex.cpp ``` struct value { public: operator int() const; struct value &operator[](const char * __ptr32 _param_1); };

extern struct value *new_value();

int json_send_error(int status)
{
struct value * v = new_value();
(void)(*v)["error"];
return 0;
}

2. clang ex.c -fms-extensions -S

ex.cpp:13:13: error: use of overloaded operator '[]' is ambiguous (with operand types 'struct value' and 'const char[6]')
13 | (void)(*v)["error"];
| ~~~~^~~~~~~~
ex.xpp:5:23: note: candidate function
5 | struct value &operator[](const char * __ptr32 _param_1);
| ^
ex.cpp:13:13: note: built-in candidate operator[](long, const char *)
13 | (void)(*v)["error"];
| ^
1 error generated.

https://godbolt.org/z/dbvEGfz13

**x64 MSVC v.19** compiles successfully https://godbolt.org/z/qWc584f5f 
</details>

[efriedma-quic]

Note MSVC gives exactly the same error if you pass /std:c++20. I'd like some explanation for why the standard version is relevant before we start making changes here.