[Bug c++/126414] New: ICE after adding explicit `this` on a hidden friend

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126414

            Bug ID: 126414
           Summary: ICE after adding explicit `this` on a hidden friend
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hanicka at hanicka dot net
  Target Milestone: ---

Following code crashes GCC starting from 14 (first version with explicit `this`
support) to current latest daily build of GCC (at CE).

```c++
struct foo {
        friend void bar(this foo) { }
};

void call_me_baby() {
    foo f;
        bar(f); // crash here, because of `this` on the friend void bar(this
foo)
}
```

in commit `7149f5ebd52eee6ad29a06f6d46c4142d0eccf46` it crashes with following
backtrace:

```
0x2b51d78 diagnostics::context::diagnostic_impl(rich_location*,
diagnostics::metadata const*, diagnostics::option_id, char const*,
__va_list_tag (*) [1], diagnostics::kind)
        ???:0
0x2b469bb internal_error(char const*, ...)
        ???:0
0xb760b7 build_new_function_call(tree_node*, vec<tree_node*, va_gc,
vl_embed>**, int)
        ???:0
0xe3585d finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool,
bool, int)
        ???:0
0xd92323 c_parse_file()
        ???:0
0xf25519 c_common_parse_file()
        ???:0
/cefs/a9/a9f609f4e529fe4607279f68_gcc-trunk-20260726/bin/../libexec/gcc/x86_64-linux-gnu/17.0.0/cc1plus
-quiet -imultiarch x86_64-linux-gnu -iprefix
/cefs/a9/a9f609f4e529fe4607279f68_gcc-trunk-20260726/bin/../lib/gcc/x86_64-linux-gnu/17.0.0/
-D_GNU_SOURCE <source> -quiet -dumpdir /app/ -dumpbase output.cpp -dumpbase-ext
.cpp -masm=intel -mtune=generic -march=x86-64 -g -O3 -std=c++23
-fdiagnostics-color=always -fno-verbose-asm -freport-bug -o /app/output.s
```

https://compiler-explorer.com/z/r698dsMfh