src/librustc_traits/normalize_projection_ty.rs

   1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use rustc::infer::canonical::{Canonical, QueryResponse};
  12 use rustc::traits::query::{normalize::NormalizationResult, CanonicalProjectionGoal, NoSolution};
  13 use rustc::traits::{self, ObligationCause, SelectionContext, TraitEngineExt};
  14 use rustc::ty::query::Providers;
  15 use rustc::ty::{ParamEnvAnd, TyCtxt};
  16 use rustc_data_structures::sync::Lrc;
  17 use std::sync::atomic::Ordering;
  18 use syntax::ast::DUMMY_NODE_ID;
  19 use syntax_pos::DUMMY_SP;
  20
  21 crate fn provide(p: &mut Providers) {
  22     *p = Providers {
  23         normalize_projection_ty,
  24         ..*p
  25     };
  26 }
  27
  28 fn normalize_projection_ty<'tcx>(
  29     tcx: TyCtxt<'_, 'tcx, 'tcx>,
  30     goal: CanonicalProjectionGoal<'tcx>,
  31 ) -> Result<Lrc<Canonical<'tcx, QueryResponse<'tcx, NormalizationResult<'tcx>>>>, NoSolution> {
  32     debug!("normalize_provider(goal={:#?})", goal);
  33
  34     tcx.sess
  35         .perf_stats
  36         .normalize_projection_ty
  37         .fetch_add(1, Ordering::Relaxed);
  38     tcx.infer_ctxt().enter_canonical_trait_query(
  39         &goal,
  40         |infcx,
  41          fulfill_cx,
  42          ParamEnvAnd {
  43              param_env,
  44              value: goal,
  45          }| {
  46             let selcx = &mut SelectionContext::new(infcx);
  47             let cause = ObligationCause::misc(DUMMY_SP, DUMMY_NODE_ID);
  48             let mut obligations = vec![];
  49             let answer = traits::normalize_projection_type(
  50                 selcx,
  51                 param_env,
  52                 goal,
  53                 cause,
  54                 0,
  55                 &mut obligations,
  56             );
  57             fulfill_cx.register_predicate_obligations(infcx, obligations);
  58             Ok(NormalizationResult {
  59                 normalized_ty: answer,
  60             })
  61         },
  62     )
  63 }