GCCRS hangs indefinitely when processing macro with $meta:meta fragment

Summary

When compiling a Rust program containing a macro that matches the meta fragment specifier, GCCRS exceeds the processing time limit and is terminated with SIGKILL. The same code compiles successfully (with warnings) under rustc.

Reproducer

I tried this code:

macro_rules! check { ($meta:meta) => () }

check!(meta(a b c d));
check!(meta[a b c d]);
check!(meta { a b c d });
check!(meta);
check!(meta = 0);

fn main() {}

Does the code make use of any (1.49) nightly feature ?

• Nightly

Godbolt link

https://godbolt.org/z/448j6hdxG

Actual behavior

Compiler hangs indefinitely and is killed with SIGKILL (exit code 143).

Expected behavior

The code should compile successfully (possibly with warnings about unused main), or report clear errors if the macro usage is invalid.

GCC Version

14.2

Start by running the Rust reproducer from the issue through GCCRS and compare it with the linked Godbolt result. Trace the macro_rules meta-fragment handling; done means the cases terminate and either compile or emit clear diagnostics rather than being killed.