compiler/rustc_traits/src/normalize_projection_ty.rs

   1 use rustc_infer::infer::canonical::{Canonical, QueryResponse};
   2 use rustc_infer::infer::TyCtxtInferExt;
   3 use rustc_infer::traits::TraitEngineExt as _;
   4 use rustc_middle::ty::query::Providers;
   5 use rustc_middle::ty::{ParamEnvAnd, TyCtxt};
   6 use rustc_trait_selection::infer::InferCtxtBuilderExt;
   7 use rustc_trait_selection::traits::query::{
   8     normalize::NormalizationResult, CanonicalProjectionGoal, NoSolution,
   9 };
  10 use rustc_trait_selection::traits::{self, ObligationCause, SelectionContext};
  11 use std::sync::atomic::Ordering;
  12
  13 pub(crate) fn provide(p: &mut Providers) {
  14     *p = Providers { normalize_projection_ty, ..*p };
  15 }
  16
  17 fn normalize_projection_ty<'tcx>(
  18     tcx: TyCtxt<'tcx>,
  19     goal: CanonicalProjectionGoal<'tcx>,
  20 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, NormalizationResult<'tcx>>>, NoSolution> {
  21     debug!("normalize_provider(goal={:#?})", goal);
  22
  23     tcx.sess.perf_stats.normalize_projection_ty.fetch_add(1, Ordering::Relaxed);
  24     tcx.infer_ctxt().enter_canonical_trait_query(
  25         &goal,
  26         |infcx, fulfill_cx, ParamEnvAnd { param_env, value: goal }| {
  27             let selcx = &mut SelectionContext::new(infcx);
  28             let cause = ObligationCause::dummy();
  29             let mut obligations = vec![];
  30             let answer = traits::normalize_projection_type(
  31                 selcx,
  32                 param_env,
  33                 goal,
  34                 cause,
  35                 0,
  36                 &mut obligations,
  37             );
  38             fulfill_cx.register_predicate_obligations(infcx, obligations);
  39             // FIXME(associated_const_equality): All users of normalize_projection_ty expected
  40             // a type, but there is the possibility it could've been a const now. Maybe change
  41             // it to a Term later?
  42             Ok(NormalizationResult { normalized_ty: answer.ty().unwrap() })
  43         },
  44     )
  45 }