[Bug c++/111079] New: Failing to reject a defaulted/deleted local function definition if it is a friend of a local class

[janschultke at googlemail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111079

            Bug ID: 111079
           Summary: Failing to reject a defaulted/deleted local function
                    definition if it is a friend of a local class
           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: ---

## Code to Reproduce A (https://godbolt.org/z/ar34vn5dT)

void foo() {
    struct A;
    bool operator ==(const A&, const A&);
    struct A { 
        friend bool operator ==(const A&, const A&);
    };
    bool operator ==(const A&, const A&) = default;
}

## Code to Reproduce B (https://godbolt.org/z/sdo9fhacb)

void foo() {
    struct A;
    bool bar(const A&, const A&);
    struct A { 
        friend bool bar(const A&, const A&);
    };
    bool bar(const A&, const A&) = delete;
}

## Expected Output

Compiler error.

## Actual Output

<source>: In function 'void foo()':
<source>:7:40: warning: declaration of 'bool operator==(const foo()::A&, const
foo()::A&)' has 'extern' and is initialized
    7 |     bool operator ==(const A&, const A&) = default;
      | 

## Explanation

According to [dcl.fct.def.general] p2:
> A function shall be defined only in namespace or class scope.

There is a definition of `operator==` at block scope, which is obviously
invalid. Operator overloads are also considered functions
([over.oper.general]), so they should be subject to the same rules.