src/librustc_traits/chalk_context/unify.rs

   1 use rustc::infer::nll_relate::{NormalizationStrategy, TypeRelating, TypeRelatingDelegate};
   2 use rustc::infer::{InferCtxt, RegionVariableOrigin};
   3 use rustc::traits::{DomainGoal, Environment, Goal, InEnvironment};
   4 use rustc::ty;
   5 use rustc::ty::relate::{Relate, RelateResult, TypeRelation};
   6 use rustc_span::DUMMY_SP;
   7
   8 crate struct UnificationResult<'tcx> {
   9     crate goals: Vec<InEnvironment<'tcx, Goal<'tcx>>>,
  10     crate constraints: Vec<super::RegionConstraint<'tcx>>,
  11 }
  12
  13 crate fn unify<'me, 'tcx, T: Relate<'tcx>>(
  14     infcx: &'me InferCtxt<'me, 'tcx>,
  15     environment: Environment<'tcx>,
  16     variance: ty::Variance,
  17     a: &T,
  18     b: &T,
  19 ) -> RelateResult<'tcx, UnificationResult<'tcx>> {
  20     debug!(
  21         "unify(
  22         a = {:?},
  23         b = {:?},
  24         environment = {:?},
  25     )",
  26         a, b, environment
  27     );
  28
  29     let mut delegate = ChalkTypeRelatingDelegate::new(infcx, environment);
  30
  31     TypeRelating::new(infcx, &mut delegate, variance).relate(a, b)?;
  32
  33     debug!("unify: goals = {:?}, constraints = {:?}", delegate.goals, delegate.constraints);
  34
  35     Ok(UnificationResult { goals: delegate.goals, constraints: delegate.constraints })
  36 }
  37
  38 struct ChalkTypeRelatingDelegate<'me, 'tcx> {
  39     infcx: &'me InferCtxt<'me, 'tcx>,
  40     environment: Environment<'tcx>,
  41     goals: Vec<InEnvironment<'tcx, Goal<'tcx>>>,
  42     constraints: Vec<super::RegionConstraint<'tcx>>,
  43 }
  44
  45 impl ChalkTypeRelatingDelegate<'me, 'tcx> {
  46     fn new(infcx: &'me InferCtxt<'me, 'tcx>, environment: Environment<'tcx>) -> Self {
  47         Self { infcx, environment, goals: Vec::new(), constraints: Vec::new() }
  48     }
  49 }
  50
  51 impl TypeRelatingDelegate<'tcx> for &mut ChalkTypeRelatingDelegate<'_, 'tcx> {
  52     fn create_next_universe(&mut self) -> ty::UniverseIndex {
  53         self.infcx.create_next_universe()
  54     }
  55
  56     fn next_existential_region_var(&mut self, _was_placeholder: bool) -> ty::Region<'tcx> {
  57         self.infcx.next_region_var(RegionVariableOrigin::MiscVariable(DUMMY_SP))
  58     }
  59
  60     fn next_placeholder_region(&mut self, placeholder: ty::PlaceholderRegion) -> ty::Region<'tcx> {
  61         self.infcx.tcx.mk_region(ty::RePlaceholder(placeholder))
  62     }
  63
  64     fn generalize_existential(&mut self, universe: ty::UniverseIndex) -> ty::Region<'tcx> {
  65         self.infcx
  66             .next_region_var_in_universe(RegionVariableOrigin::MiscVariable(DUMMY_SP), universe)
  67     }
  68
  69     fn push_outlives(&mut self, sup: ty::Region<'tcx>, sub: ty::Region<'tcx>) {
  70         self.constraints.push(ty::OutlivesPredicate(sup.into(), sub));
  71     }
  72
  73     fn push_domain_goal(&mut self, domain_goal: DomainGoal<'tcx>) {
  74         let goal = self.environment.with(self.infcx.tcx.mk_goal(domain_goal.into_goal()));
  75         self.goals.push(goal);
  76     }
  77
  78     fn normalization() -> NormalizationStrategy {
  79         NormalizationStrategy::Lazy
  80     }
  81
  82     fn forbid_inference_vars() -> bool {
  83         false
  84     }
  85 }