compiler/rustc_typeck/src/check/inherited.rs

   1 use super::callee::DeferredCallResolution;
   2 use super::MaybeInProgressTables;
   3
   4 use rustc_data_structures::fx::FxHashSet;
   5 use rustc_hir as hir;
   6 use rustc_hir::def_id::{DefIdMap, LocalDefId};
   7 use rustc_hir::HirIdMap;
   8 use rustc_infer::infer;
   9 use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
  10 use rustc_middle::ty::fold::TypeFoldable;
  11 use rustc_middle::ty::{self, Ty, TyCtxt};
  12 use rustc_span::{self, Span};
  13 use rustc_trait_selection::infer::InferCtxtExt as _;
  14 use rustc_trait_selection::traits::{self, ObligationCause, TraitEngine, TraitEngineExt};
  15
  16 use std::cell::RefCell;
  17 use std::ops::Deref;
  18
  19 /// Closures defined within the function. For example:
  20 ///
  21 ///     fn foo() {
  22 ///         bar(move|| { ... })
  23 ///     }
  24 ///
  25 /// Here, the function `foo()` and the closure passed to
  26 /// `bar()` will each have their own `FnCtxt`, but they will
  27 /// share the inherited fields.
  28 pub struct Inherited<'a, 'tcx> {
  29     pub(super) infcx: InferCtxt<'a, 'tcx>,
  30
  31     pub(super) typeck_results: super::MaybeInProgressTables<'a, 'tcx>,
  32
  33     pub(super) locals: RefCell<HirIdMap<super::LocalTy<'tcx>>>,
  34
  35     pub(super) fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
  36
  37     // Some additional `Sized` obligations badly affect type inference.
  38     // These obligations are added in a later stage of typeck.
  39     pub(super) deferred_sized_obligations:
  40         RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
  41
  42     // When we process a call like `c()` where `c` is a closure type,
  43     // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
  44     // `FnOnce` closure. In that case, we defer full resolution of the
  45     // call until upvar inference can kick in and make the
  46     // decision. We keep these deferred resolutions grouped by the
  47     // def-id of the closure, so that once we decide, we can easily go
  48     // back and process them.
  49     pub(super) deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'tcx>>>>,
  50
  51     pub(super) deferred_cast_checks: RefCell<Vec<super::cast::CastCheck<'tcx>>>,
  52
  53     pub(super) deferred_generator_interiors:
  54         RefCell<Vec<(hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
  55
  56     /// Reports whether this is in a const context.
  57     pub(super) constness: hir::Constness,
  58
  59     pub(super) body_id: Option<hir::BodyId>,
  60
  61     /// Whenever we introduce an adjustment from `!` into a type variable,
  62     /// we record that type variable here. This is later used to inform
  63     /// fallback. See the `fallback` module for details.
  64     pub(super) diverging_type_vars: RefCell<FxHashSet<Ty<'tcx>>>,
  65 }
  66
  67 impl<'a, 'tcx> Deref for Inherited<'a, 'tcx> {
  68     type Target = InferCtxt<'a, 'tcx>;
  69     fn deref(&self) -> &Self::Target {
  70         &self.infcx
  71     }
  72 }
  73
  74 /// Helper type of a temporary returned by `Inherited::build(...)`.
  75 /// Necessary because we can't write the following bound:
  76 /// `F: for<'b, 'tcx> where 'tcx FnOnce(Inherited<'b, 'tcx>)`.
  77 pub struct InheritedBuilder<'tcx> {
  78     infcx: infer::InferCtxtBuilder<'tcx>,
  79     def_id: LocalDefId,
  80 }
  81
  82 impl Inherited<'_, 'tcx> {
  83     pub fn build(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> InheritedBuilder<'tcx> {
  84         let hir_owner = tcx.hir().local_def_id_to_hir_id(def_id).owner;
  85
  86         InheritedBuilder {
  87             infcx: tcx.infer_ctxt().with_fresh_in_progress_typeck_results(hir_owner),
  88             def_id,
  89         }
  90     }
  91 }
  92
  93 impl<'tcx> InheritedBuilder<'tcx> {
  94     pub fn enter<F, R>(&mut self, f: F) -> R
  95     where
  96         F: for<'a> FnOnce(Inherited<'a, 'tcx>) -> R,
  97     {
  98         let def_id = self.def_id;
  99         self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
 100     }
 101 }
 102
 103 impl Inherited<'a, 'tcx> {
 104     pub(super) fn new(infcx: InferCtxt<'a, 'tcx>, def_id: LocalDefId) -> Self {
 105         let tcx = infcx.tcx;
 106         let item_id = tcx.hir().local_def_id_to_hir_id(def_id);
 107         Self::with_constness(infcx, def_id, tcx.hir().get(item_id).constness_for_typeck())
 108     }
 109
 110     pub(super) fn with_constness(
 111         infcx: InferCtxt<'a, 'tcx>,
 112         def_id: LocalDefId,
 113         constness: hir::Constness,
 114     ) -> Self {
 115         let tcx = infcx.tcx;
 116         let item_id = tcx.hir().local_def_id_to_hir_id(def_id);
 117         let body_id = tcx.hir().maybe_body_owned_by(item_id);
 118
 119         Inherited {
 120             typeck_results: MaybeInProgressTables {
 121                 maybe_typeck_results: infcx.in_progress_typeck_results,
 122             },
 123             infcx,
 124             fulfillment_cx: RefCell::new(<dyn TraitEngine<'_>>::new(tcx)),
 125             locals: RefCell::new(Default::default()),
 126             deferred_sized_obligations: RefCell::new(Vec::new()),
 127             deferred_call_resolutions: RefCell::new(Default::default()),
 128             deferred_cast_checks: RefCell::new(Vec::new()),
 129             deferred_generator_interiors: RefCell::new(Vec::new()),
 130             diverging_type_vars: RefCell::new(Default::default()),
 131             constness,
 132             body_id,
 133         }
 134     }
 135
 136     pub(super) fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
 137         debug!("register_predicate({:?})", obligation);
 138         if obligation.has_escaping_bound_vars() {
 139             span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}", obligation);
 140         }
 141         self.fulfillment_cx.borrow_mut().register_predicate_obligation(self, obligation);
 142     }
 143
 144     pub(super) fn register_predicates<I>(&self, obligations: I)
 145     where
 146         I: IntoIterator<Item = traits::PredicateObligation<'tcx>>,
 147     {
 148         for obligation in obligations {
 149             self.register_predicate(obligation);
 150         }
 151     }
 152
 153     pub(super) fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
 154         self.register_predicates(infer_ok.obligations);
 155         infer_ok.value
 156     }
 157
 158     pub(super) fn normalize_associated_types_in<T>(
 159         &self,
 160         span: Span,
 161         body_id: hir::HirId,
 162         param_env: ty::ParamEnv<'tcx>,
 163         value: T,
 164     ) -> T
 165     where
 166         T: TypeFoldable<'tcx>,
 167     {
 168         self.normalize_associated_types_in_with_cause(
 169             ObligationCause::misc(span, body_id),
 170             param_env,
 171             value,
 172         )
 173     }
 174
 175     pub(super) fn normalize_associated_types_in_with_cause<T>(
 176         &self,
 177         cause: ObligationCause<'tcx>,
 178         param_env: ty::ParamEnv<'tcx>,
 179         value: T,
 180     ) -> T
 181     where
 182         T: TypeFoldable<'tcx>,
 183     {
 184         let ok = self.partially_normalize_associated_types_in(cause, param_env, value);
 185         debug!(?ok);
 186         self.register_infer_ok_obligations(ok)
 187     }
 188 }