[BUG] Unable to call a member function on a heap object.

[guybrush77]

Describe the bug

Unable to call a member function on a heap object.

To Reproduce

I am presuming the following should work seamlessly:

// test.cpp2
foo : type = {
    print: (this) = std::cout << "Hello!\n";
}

main: () = {
    f := new<foo>;
    f*.print();
}

Transpiling works:

cppfront -version
cppfront compiler v0.2.1   Build 8910:1255

cppfront -p test.cpp2 
test.cpp2... ok (all Cpp2, passes safety checks)

Compiling fails:

clang++-15 -std=c++20 test.cpp
test.cpp2:8:17: error: use of undeclared identifier 'print'
CPP2_UFCS_0(print, (*cpp2::assert_not_null(std::move(f))));

[JohelEGP]

The error message is bad due to #439.
Here's what I get using Clang with #506:

Waarudo.cpp2:220:3: error: no matching function for call to object of type '(lambda at Waarudo.cpp2:220:3)'
  220 |   CPP2_UFCS(print)((*cpp2::assert_not_null(std::move(f))));
      |   ^~~~~~~~~~~~~~~~
/home/johel/root/include/cpp2util_macros.h:104:42: note: expanded from macro 'CPP2_UFCS'
  104 | #define CPP2_UFCS(...)                   CPP2_UFCS_(&,,__VA_ARGS__)
      |                                          ^~~~~~~~~~~~~~~~~~~~~~~~~~
/home/johel/root/include/cpp2util_macros.h:88:46: note: expanded from macro 'CPP2_UFCS_'
   88 | #define CPP2_UFCS_(LAMBDADEFCAPT,TEMPKW,...) \
      |                                              ^
   89 | [LAMBDADEFCAPT] CPP2_LAMBDA_NO_DISCARD (auto&& obj, auto&& ...params) CPP2_FORCE_INLINE_LAMBDA_CLANG \
      | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   90 |   noexcept(requires { requires requires { CPP2_FORWARD(obj).TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...); }; \
      |   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   91 |                       requires noexcept(CPP2_FORWARD(obj).TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...)); } \
      |                       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   92 |            || requires { requires !requires { CPP2_FORWARD(obj).TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...); }; \
      |            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   93 |                          requires noexcept(__VA_ARGS__(CPP2_FORWARD(obj), CPP2_FORWARD(params)...)); }) \
      |                          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   94 |     CPP2_FORCE_INLINE_LAMBDA -> decltype(auto) \
      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   95 |     requires requires { CPP2_FORWARD(obj).TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...); } \
      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   96 |              || requires { __VA_ARGS__(CPP2_FORWARD(obj), CPP2_FORWARD(params)...); } { \
      |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   97 |     if constexpr (requires{ CPP2_FORWARD(obj).TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...); }) { \
      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   98 |         return CPP2_FORWARD(obj).TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...); \
      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   99 |     } else { \
      |     ~~~~~~~~~~
  100 |         return __VA_ARGS__(CPP2_FORWARD(obj), CPP2_FORWARD(params)...); \
      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  101 |     } \
      |     ~~~
Waarudo.cpp2:220:3: note: candidate template ignored: constraints not satisfied [with obj:auto = std::__1::unique_ptr<foo> (&)(), params:auto = <>]
/home/johel/root/include/cpp2util_macros.h:104:42: note: expanded from macro 'CPP2_UFCS'
  104 | #define CPP2_UFCS(...)                   CPP2_UFCS_(&,,__VA_ARGS__)
      |                                          ^
/home/johel/root/include/cpp2util_macros.h:88:46: note: expanded from macro 'CPP2_UFCS_'
   88 | #define CPP2_UFCS_(LAMBDADEFCAPT,TEMPKW,...) \
      |                                              ^
Waarudo.cpp2:220:3: note: because 'std::forward<decltype(obj)>(obj).print(std::forward<decltype(params)>(params)...)' would be invalid: member reference base type 'std::__1::unique_ptr<foo> ()' is not a structure or union
/home/johel/root/include/cpp2util_macros.h:104:42: note: expanded from macro 'CPP2_UFCS'
  104 | #define CPP2_UFCS(...)                   CPP2_UFCS_(&,,__VA_ARGS__)
      |                                          ^
/home/johel/root/include/cpp2util_macros.h:95:42: note: expanded from macro 'CPP2_UFCS_'
   95 |     requires requires { CPP2_FORWARD(obj).TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...); } \
      |                                          ^
Waarudo.cpp2:220:13: note: and 'print(std::forward<decltype(obj)>(obj), std::forward<decltype(params)>(params)...)' would be invalid: no matching function for call to 'print'
  220 |   CPP2_UFCS(print)((*cpp2::assert_not_null(std::move(f))));
      |             ^
1 error generated.

new<foo> lowers to the template-id cpp2_new<foo>, which is a function pointer.
What you want to use instead is new<foo>().

[guybrush77]

@JohelEGP Thanks, that makes sense. I will close this bug.

[JohelEGP]

Maybe new<foo> should reference a callable object of non-copyable type.
Then this bug could have been prevented.
But something like :(_) = {}(new<foo>) would still work.