Summary

It seems like recursive macros aren't being expanded correctly. Notably, the issue seems to go away if the metavariable isn't an ident.

Reproducer

I tried this code:

#![allow(path_statements)]

macro_rules! array_impl_default {
    {$t:ident} => {
        $t;
        array_impl_default!{}
    };
    {} => {};
}

pub fn foo() {
    let x = 12;
    array_impl_default! {x}
}

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

• Nightly

Godbolt link

https://godbolt.org/z/Mbd1cdYhb

Actual behavior

An infinite loop

Expected behavior

Compiles

GCC Version

85ec714