src/librustc_traits/normalize_projection_ty.rs

   1 use rustc::infer::canonical::{Canonical, QueryResponse};
   2 use rustc::traits::query::{normalize::NormalizationResult, CanonicalProjectionGoal, NoSolution};
   3 use rustc::traits::{self, ObligationCause, SelectionContext, TraitEngineExt};
   4 use rustc::ty::query::Providers;
   5 use rustc::ty::{ParamEnvAnd, TyCtxt};
   6 use rustc_hir as hir;
   7 use rustc_span::DUMMY_SP;
   8 use std::sync::atomic::Ordering;
   9
  10 crate fn provide(p: &mut Providers<'_>) {
  11     *p = Providers { normalize_projection_ty, ..*p };
  12 }
  13
  14 fn normalize_projection_ty<'tcx>(
  15     tcx: TyCtxt<'tcx>,
  16     goal: CanonicalProjectionGoal<'tcx>,
  17 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, NormalizationResult<'tcx>>>, NoSolution> {
  18     debug!("normalize_provider(goal={:#?})", goal);
  19
  20     tcx.sess.perf_stats.normalize_projection_ty.fetch_add(1, Ordering::Relaxed);
  21     tcx.infer_ctxt().enter_canonical_trait_query(
  22         &goal,
  23         |infcx, fulfill_cx, ParamEnvAnd { param_env, value: goal }| {
  24             let selcx = &mut SelectionContext::new(infcx);
  25             let cause = ObligationCause::misc(DUMMY_SP, hir::DUMMY_HIR_ID);
  26             let mut obligations = vec![];
  27             let answer = traits::normalize_projection_type(
  28                 selcx,
  29                 param_env,
  30                 goal,
  31                 cause,
  32                 0,
  33                 &mut obligations,
  34             );
  35             fulfill_cx.register_predicate_obligations(infcx, obligations);
  36             Ok(NormalizationResult { normalized_ty: answer })
  37         },
  38     )
  39 }