[Clang] nontrivial use of std::source_location::current() in a default argument fails

[pdimov]

The following

#include <source_location>

#define BOOST_CURRENT_LOCATION_PTR \
    []( char const* fn ) \
    { \
        static constexpr std::source_location loc = std::source_location::current(); \
        return &loc; \
    }( std::source_location::current().function_name() )

auto f( std::source_location const* loc = BOOST_CURRENT_LOCATION_PTR )
{
    return loc;
}

auto g()
{
    return f();
}

fails (for Clang trunk and Clang 17, with both libstdc++ and libc++) with

error: cannot take address of consteval function 'current' outside of an immediate invocation

(https://godbolt.org/z/jqqxq6njh)

GCC, MSVC accept.

The example is simplified to the point of doing not much at all, but it started out as something doing useful things. :-)

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Peter Dimov (pdimov)

The following ``` #include <source_location>

#define BOOST_CURRENT_LOCATION_PTR
[]( char const* fn )
{
static constexpr std::source_location loc = std::source_location::current();
return &loc;
}( std::source_location::current().function_name() )

auto f( std::source_location const* loc = BOOST_CURRENT_LOCATION_PTR )
{
return loc;
}

auto g()
{
return f();
}

fails (for Clang trunk and Clang 17, with both libstdc++ and libc++) with

error: cannot take address of consteval function 'current' outside of an immediate invocation

(https://godbolt.org/z/jqqxq6njh)

GCC, MSVC accept.

The example is simplified to the point of doing not much at all, but it started out as something doing useful things. :-)
</details>

[shafik]

CC @cor3ntin

[cor3ntin]

Given

consteval const char* ce() {
    return "Hello";
}
auto f2(const char* loc = []( char const* fn )
    { return fn; }  ( ce() ) ) // #1
{
    return loc;
}

auto g() {
    return f2();
}

ImmediateCallVisitor files to visit the call to ce #1. I am really puzzled as to why