Explicit object operator() copies movable temporaries

[Fedr]

This program

struct A {
    A() {}
    A(A&&) = default;
    void operator() (this A) {}
};

int main() {
    A{}.operator()(); // ok
    A{}();            // fails in Clang
}

is accepted by GCC and MSVC, but not in Clang, which tries to copy A in A{}();:

error: call to implicitly-deleted copy constructor of 'A'
    9 |     A{}();            // fails in Clang
      |     ^~~
<source>:3:5: note: copy constructor is implicitly deleted because 'A' has a user-declared move constructor
    3 |     A(A&&) = default;
      |     ^
<source>:4:28: note: passing argument to parameter here
    4 |     void operator() (this A) {}
      |               

Online demo: https://gcc.godbolt.org/z/YEKh8G71o

[MitalAshok]

Duplicate of #100341

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Fedor Chelnokov (Fedr)

This program ``` struct A { A() {} A(A&&) = default; void operator() (this A) {} };

int main() {
A{}.operator()(); // ok
A{}(); // fails in Clang
}

is accepted by GCC and MSVC, but not in Clang, which tries to copy `A` in `A{}();`:

error: call to implicitly-deleted copy constructor of 'A'
9 | A{}(); // fails in Clang
| ^~~
<source>:3:5: note: copy constructor is implicitly deleted because 'A' has a user-declared move constructor
3 | A(A&&) = default;
| ^
<source>:4:28: note: passing argument to parameter here
4 | void operator() (this A) {}
|

Online demo: https://gcc.godbolt.org/z/YEKh8G71o
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