`main()` returning a type that implements `Termination` with an unsatisfied lifetime bound gives a linker error

[theemathas]

I tried this code:

use std::process::ExitCode;
use std::process::Termination;

trait IsStatic {}
impl<'a: 'static> IsStatic for &'a () {}

struct Thing;
impl Termination for Thing where for<'a> &'a (): IsStatic {
    fn report(self) -> ExitCode { panic!() }
}

fn main() -> Thing { Thing }

I expected a normal compiler error. Instead, I got the following:

error: linking with `cc` failed: exit status: 1
  |
  = note:  "cc" ....... <arguments omitted for brevity of this issue>
  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: rust-lld: error: undefined hidden symbol: std::rt::lang_start::h005004333204f9e0
          >>> referenced by playground.b3525d8026055c0f-cgu.0
          >>>               /playground/target/debug/deps/playground-65a1e30147052435.playground.b3525d8026055c0f-cgu.0.rcgu.o:(main)
          collect2: error: ld returned 1 exit status

Meta

Reproducible on the playground with version 1.93.0-nightly (2025-11-01 bd3ac0330018c23b111b)

[lcnr]

need to call infcx.check_regions here

rust/compiler/rustc_hir_analysis/src/check/entry.rs

Lines 125 to 148 in a417515

	if let Some(term_did) = tcx.lang_items().termination() {
	let return_ty = main_fnsig.output();
	let return_ty_span = main_fn_return_type_span(tcx, main_def_id).unwrap_or(main_span);
	let Some(return_ty) = return_ty.no_bound_vars() else {
	tcx.dcx().emit_err(errors::MainFunctionReturnTypeGeneric { span: return_ty_span });
	return;
	};
	let infcx = tcx.infer_ctxt().build(TypingMode::non_body_analysis());
	let cause = traits::ObligationCause::new(
	return_ty_span,
	main_diagnostics_def_id,
	ObligationCauseCode::MainFunctionType,
	);
	let ocx = traits::ObligationCtxt::new_with_diagnostics(&infcx);
	let norm_return_ty = ocx.normalize(&cause, param_env, return_ty);
	ocx.register_bound(cause, param_env, norm_return_ty, term_did);
	let errors = ocx.evaluate_obligations_error_on_ambiguity();
	if !errors.is_empty() {
	infcx.err_ctxt().report_fulfillment_errors(errors);
	error = true;
	}
	// now we can take the return type of the given main function
	expected_return_type = norm_return_ty;
	} else {

[lcnr]

I generally feel like we should clean up entry-fn wf checking to use the WfCheckingCtxt instead of manually creating its infcx + ocx

[bjorn3]

The only way to construct a WfCheckingCtxt outside of wfcheck.rs is using enter_wf_checking_ctxt, which doesn't allow specifying a ParamEnv and only works for local bodies.