[BUG] [Clang] UFCS on identifier also declared at type scope fails

[JohelEGP]

Title: [Clang] UFCS on shared identifier between types in non-this member function.

Description:

The type of this and the unrelated type share f.
In a non-this member function,
UFCS on f with the unrelated type breaks Clang.
GCC and MSVC work, so it may be a Clang bug: https://compiler-explorer.com/z/vEEovohd3.

Minimal reproducer (https://cpp2.godbolt.org/z/qWjx6Pav7):

t: type = {
  f: (this) = { }
}
u: type = {
  f: (this) = { }
  g: (inout self: u) = {
    a: t = ();
    a.f();
  }
}
main: () = { }

Commands:

cppfront main.cpp2
clang++17 -std=c++23 -stdlib=libc++ -lc++abi -pedantic-errors -Wall -Wextra -Wconversion -I . main.cpp

Expected result: A working program.

Actual result and error:

Cpp2 lowered to Cpp1:

//=== Cpp2 type declarations ====================================================


#include "cpp2util.h"

class t;
  

class u;
  

//=== Cpp2 type definitions and function declarations ===========================

class t {
  public: auto f() const -> void;

  public: t() = default;
  public: t(t const&) = delete; /* No 'that' constructor, suppress copy */
  public: auto operator=(t const&) -> void = delete;
};
class u {
  public: auto f() const -> void;
  public: static auto g(u& self) -> void;
    
  public: u() = default;
  public: u(u const&) = delete; /* No 'that' constructor, suppress copy */
  public: auto operator=(u const&) -> void = delete;


};
auto main() -> int;


//=== Cpp2 function definitions =================================================


  auto t::f() const -> void{}

  auto u::f() const -> void{}
  auto u::g(u& self) -> void{
    t a {}; 
    CPP2_UFCS_0(f, std::move(a));
  }

auto main() -> int{}

Output:

main.cpp2:8:17: error: call to non-static member function without an object argument
    8 |     CPP2_UFCS_0(f, std::move(a));
      |                 ^
raw.githubusercontent.com/hsutter/cppfront/main/include/cpp2util.h:727:16: note: expanded from macro 'CPP2_UFCS_0'
  727 |         return FUNCNAME(CPP2_FORWARD(obj)); \
      |                ^~~~~~~~
1 error generated.

[JohelEGP]

May be related to llvm/llvm-project#58872.

[JohelEGP]

You don't actually need to involve other types (https://cpp2.godbolt.org/z/qo6PErbYq, https://compiler-explorer.com/z/EeMsaj1ca):

t: @struct type = {
  f: (this) = { }
  g: (x) = x.f();
}
main: () = { }

//=== Cpp2 type declarations ====================================================


#include "cpp2util.h"

class t;
  

//=== Cpp2 type definitions and function declarations ===========================

class t {
  public: auto f() const -> void;
  public: static auto g(auto const& x) -> void;
};
auto main() -> int;


//=== Cpp2 function definitions =================================================


  auto t::f() const -> void{}
  auto t::g(auto const& x) -> void { CPP2_UFCS_0(f, x);  }

auto main() -> int{}

main.cpp2:3:50: error: call to non-static member function without an object argument
    3 |   auto t::g(auto const& x) -> void { CPP2_UFCS_0(f, x);  }
      |                                                  ^
raw.githubusercontent.com/hsutter/cppfront/main/include/cpp2util.h:701:16: note: expanded from macro 'CPP2_UFCS_0'
  701 |         return FUNCNAME(CPP2_FORWARD(obj)); \
      |                ^~~~~~~~
1 error generated.

[JakeShirley]

Hitting this with Apple Clang 14.0