src/librustc_traits/normalize_projection_ty.rs

   1 use rustc::hir;
   2 use rustc::infer::canonical::{Canonical, QueryResponse};
   3 use rustc::traits::query::{normalize::NormalizationResult, CanonicalProjectionGoal, NoSolution};
   4 use rustc::traits::{self, ObligationCause, SelectionContext, TraitEngineExt};
   5 use rustc::ty::query::Providers;
   6 use rustc::ty::{ParamEnvAnd, TyCtxt};
   7 use std::sync::atomic::Ordering;
   8 use syntax_pos::DUMMY_SP;
   9
  10 crate fn provide(p: &mut Providers<'_>) {
  11     *p = Providers {
  12         normalize_projection_ty,
  13         ..*p
  14     };
  15 }
  16
  17 fn normalize_projection_ty<'tcx>(
  18     tcx: TyCtxt<'_, 'tcx, '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
  24         .perf_stats
  25         .normalize_projection_ty
  26         .fetch_add(1, Ordering::Relaxed);
  27     tcx.infer_ctxt().enter_canonical_trait_query(
  28         &goal,
  29         |infcx,
  30          fulfill_cx,
  31          ParamEnvAnd {
  32              param_env,
  33              value: goal,
  34          }| {
  35             let selcx = &mut SelectionContext::new(infcx);
  36             let cause = ObligationCause::misc(DUMMY_SP, hir::DUMMY_HIR_ID);
  37             let mut obligations = vec![];
  38             let answer = traits::normalize_projection_type(
  39                 selcx,
  40                 param_env,
  41                 goal,
  42                 cause,
  43                 0,
  44                 &mut obligations,
  45             );
  46             fulfill_cx.register_predicate_obligations(infcx, obligations);
  47             Ok(NormalizationResult {
  48                 normalized_ty: answer,
  49             })
  50         },
  51     )
  52 }