rustc_traits/
evaluate_obligation.rs

1use rustc_infer::infer::TyCtxtInferExt;
2use rustc_middle::query::Providers;
3use rustc_middle::ty::{ParamEnvAnd, TyCtxt};
4use rustc_span::DUMMY_SP;
5use rustc_trait_selection::traits::query::CanonicalPredicateGoal;
6use rustc_trait_selection::traits::{
7    EvaluationResult, Obligation, ObligationCause, OverflowError, SelectionContext, TraitQueryMode,
8};
9use tracing::debug;
10
11pub(crate) fn provide(p: &mut Providers) {
12    *p = Providers { evaluate_obligation, ..*p };
13}
14
15fn evaluate_obligation<'tcx>(
16    tcx: TyCtxt<'tcx>,
17    canonical_goal: CanonicalPredicateGoal<'tcx>,
18) -> Result<EvaluationResult, OverflowError> {
19    assert!(!tcx.next_trait_solver_globally());
20    debug!("evaluate_obligation(canonical_goal={:#?})", canonical_goal);
21    let (ref infcx, goal, _canonical_inference_vars) =
22        tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &canonical_goal);
23    debug!("evaluate_obligation: goal={:#?}", goal);
24    let ParamEnvAnd { param_env, value: predicate } = goal;
25
26    let mut selcx = SelectionContext::with_query_mode(infcx, TraitQueryMode::Canonical);
27    let obligation = Obligation::new(tcx, ObligationCause::dummy(), param_env, predicate);
28
29    selcx.evaluate_root_obligation(&obligation)
30}