explicit tail calls: hang in const eval of recursive call

[matthiaskrgr]

I tried this code:

#![expect(incomplete_features)]
#![feature(explicit_tail_calls)]

pub const fn f() {
    become g();
}

const fn g() {
    become g();
}

const _: () = f();

fn main() {}

It seems there is no output here until I ctrl+c this.
perf top shows some activity in _RNvMs_NtNtCs69nEItziXW1_16rustc_const_eval9interpret4callINtNtB6_12eval_context8InterpCxNtNtNtB8_10const_eval7machine18CompileTimeMachineE16init_stac

Meta

rustc --version --verbose:

rustc 1.90.0-nightly (adcb3d3b4 2025-07-31)
binary: rustc
commit-hash: adcb3d3b4cd3b7c4cde642f3ed537037f293738e
commit-date: 2025-07-31
host: x86_64-unknown-linux-gnu
release: 1.90.0-nightly
LLVM version: 20.1.8

[matthiaskrgr]

^Cerror[E0080]: compilation was interrupted
  --> a.rs:12:15
   |
12 | const _: () = f();
   |               ^^^ evaluation of `_` failed inside this call
   |
note: inside `g`
  --> a.rs:9:5
   |
 9 |     become g();
   |     ^^^^^^^^^^ the failure occurred here

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0080`.

[WaffleLapkin]

Thanks for reporting this!