src/librustc_traits/normalize_projection_ty.rs

   1 use rustc::ty::query::Providers;
   2 use rustc::ty::{ParamEnvAnd, TyCtxt};
   3 use rustc_hir as hir;
   4 use rustc_infer::infer::canonical::{Canonical, QueryResponse};
   5 use rustc_infer::infer::TyCtxtInferExt;
   6 use rustc_infer::traits::TraitEngineExt as _;
   7 use rustc_span::DUMMY_SP;
   8 use rustc_trait_selection::infer::InferCtxtBuilderExt;
   9 use rustc_trait_selection::traits::query::{
  10     normalize::NormalizationResult, CanonicalProjectionGoal, NoSolution,
  11 };
  12 use rustc_trait_selection::traits::{self, ObligationCause, SelectionContext};
  13 use std::sync::atomic::Ordering;
  14
  15 crate fn provide(p: &mut Providers<'_>) {
  16     *p = Providers { normalize_projection_ty, ..*p };
  17 }
  18
  19 fn normalize_projection_ty<'tcx>(
  20     tcx: TyCtxt<'tcx>,
  21     goal: CanonicalProjectionGoal<'tcx>,
  22 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, NormalizationResult<'tcx>>>, NoSolution> {
  23     debug!("normalize_provider(goal={:#?})", goal);
  24
  25     tcx.sess.perf_stats.normalize_projection_ty.fetch_add(1, Ordering::Relaxed);
  26     tcx.infer_ctxt().enter_canonical_trait_query(
  27         &goal,
  28         |infcx, fulfill_cx, ParamEnvAnd { param_env, value: goal }| {
  29             let selcx = &mut SelectionContext::new(infcx);
  30             let cause = ObligationCause::misc(DUMMY_SP, hir::DUMMY_HIR_ID);
  31             let mut obligations = vec![];
  32             let answer = traits::normalize_projection_type(
  33                 selcx,
  34                 param_env,
  35                 goal,
  36                 cause,
  37                 0,
  38                 &mut obligations,
  39             );
  40             fulfill_cx.register_predicate_obligations(infcx, obligations);
  41             Ok(NormalizationResult { normalized_ty: answer })
  42         },
  43     )
  44 }