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