compiler/rustc_hir_typeck/src/inherited.rs

   1 use super::callee::DeferredCallResolution;
   2
   3 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
   4 use rustc_hir as hir;
   5 use rustc_hir::def_id::LocalDefId;
   6 use rustc_hir::HirIdMap;
   7 use rustc_infer::infer;
   8 use rustc_infer::infer::{DefiningAnchor, InferCtxt, InferOk, TyCtxtInferExt};
   9 use rustc_middle::ty::visit::TypeVisitable;
  10 use rustc_middle::ty::{self, Ty, TyCtxt};
  11 use rustc_span::def_id::LocalDefIdMap;
  12 use rustc_span::{self, Span};
  13 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
  14 use rustc_trait_selection::traits::{self, PredicateObligation, TraitEngine, TraitEngineExt as _};
  15
  16 use std::cell::RefCell;
  17 use std::ops::Deref;
  18
  19 /// Closures defined within the function. For example:
  20 /// ```ignore (illustrative)
  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<'tcx> {
  29     pub(super) infcx: InferCtxt<'tcx>,
  30
  31     pub(super) typeck_results: RefCell<ty::TypeckResults<'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     /// Removing these may also cause additional complications, see #101066.
  40     pub(super) deferred_sized_obligations:
  41         RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
  42
  43     /// When we process a call like `c()` where `c` is a closure type,
  44     /// we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
  45     /// `FnOnce` closure. In that case, we defer full resolution of the
  46     /// call until upvar inference can kick in and make the
  47     /// decision. We keep these deferred resolutions grouped by the
  48     /// def-id of the closure, so that once we decide, we can easily go
  49     /// back and process them.
  50     pub(super) deferred_call_resolutions: RefCell<LocalDefIdMap<Vec<DeferredCallResolution<'tcx>>>>,
  51
  52     pub(super) deferred_cast_checks: RefCell<Vec<super::cast::CastCheck<'tcx>>>,
  53
  54     pub(super) deferred_transmute_checks: RefCell<Vec<(Ty<'tcx>, Ty<'tcx>, hir::HirId)>>,
  55
  56     pub(super) deferred_asm_checks: RefCell<Vec<(&'tcx hir::InlineAsm<'tcx>, hir::HirId)>>,
  57
  58     pub(super) deferred_generator_interiors:
  59         RefCell<Vec<(LocalDefId, hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
  60
  61     pub(super) body_id: Option<hir::BodyId>,
  62
  63     /// Whenever we introduce an adjustment from `!` into a type variable,
  64     /// we record that type variable here. This is later used to inform
  65     /// fallback. See the `fallback` module for details.
  66     pub(super) diverging_type_vars: RefCell<FxHashSet<Ty<'tcx>>>,
  67
  68     pub(super) infer_var_info: RefCell<FxHashMap<ty::TyVid, ty::InferVarInfo>>,
  69 }
  70
  71 impl<'tcx> Deref for Inherited<'tcx> {
  72     type Target = InferCtxt<'tcx>;
  73     fn deref(&self) -> &Self::Target {
  74         &self.infcx
  75     }
  76 }
  77
  78 /// A temporary returned by `Inherited::build(...)`. This is necessary
  79 /// for multiple `InferCtxt` to share the same `typeck_results`
  80 /// without using `Rc` or something similar.
  81 pub struct InheritedBuilder<'tcx> {
  82     infcx: infer::InferCtxtBuilder<'tcx>,
  83     def_id: LocalDefId,
  84     typeck_results: RefCell<ty::TypeckResults<'tcx>>,
  85 }
  86
  87 impl<'tcx> Inherited<'tcx> {
  88     pub fn build(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> InheritedBuilder<'tcx> {
  89         let hir_owner = tcx.hir().local_def_id_to_hir_id(def_id).owner;
  90
  91         InheritedBuilder {
  92             infcx: tcx
  93                 .infer_ctxt()
  94                 .ignoring_regions()
  95                 .with_opaque_type_inference(DefiningAnchor::Bind(hir_owner.def_id)),
  96             def_id,
  97             typeck_results: RefCell::new(ty::TypeckResults::new(hir_owner)),
  98         }
  99     }
 100 }
 101
 102 impl<'tcx> InheritedBuilder<'tcx> {
 103     pub fn enter<F, R>(mut self, f: F) -> R
 104     where
 105         F: FnOnce(&Inherited<'tcx>) -> R,
 106     {
 107         let def_id = self.def_id;
 108         f(&Inherited::new(self.infcx.build(), def_id, self.typeck_results))
 109     }
 110 }
 111
 112 impl<'tcx> Inherited<'tcx> {
 113     fn new(
 114         infcx: InferCtxt<'tcx>,
 115         def_id: LocalDefId,
 116         typeck_results: RefCell<ty::TypeckResults<'tcx>>,
 117     ) -> Self {
 118         let tcx = infcx.tcx;
 119         let body_id = tcx.hir().maybe_body_owned_by(def_id);
 120
 121         Inherited {
 122             typeck_results,
 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_transmute_checks: RefCell::new(Vec::new()),
 130             deferred_asm_checks: RefCell::new(Vec::new()),
 131             deferred_generator_interiors: RefCell::new(Vec::new()),
 132             diverging_type_vars: RefCell::new(Default::default()),
 133             body_id,
 134             infer_var_info: RefCell::new(Default::default()),
 135         }
 136     }
 137
 138     #[instrument(level = "debug", skip(self))]
 139     pub(super) fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
 140         if obligation.has_escaping_bound_vars() {
 141             span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}", obligation);
 142         }
 143
 144         self.update_infer_var_info(&obligation);
 145
 146         self.fulfillment_cx.borrow_mut().register_predicate_obligation(self, obligation);
 147     }
 148
 149     pub(super) fn register_predicates<I>(&self, obligations: I)
 150     where
 151         I: IntoIterator<Item = traits::PredicateObligation<'tcx>>,
 152     {
 153         for obligation in obligations {
 154             self.register_predicate(obligation);
 155         }
 156     }
 157
 158     pub(super) fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
 159         self.register_predicates(infer_ok.obligations);
 160         infer_ok.value
 161     }
 162
 163     pub fn update_infer_var_info(&self, obligation: &PredicateObligation<'tcx>) {
 164         let infer_var_info = &mut self.infer_var_info.borrow_mut();
 165
 166         // (*) binder skipped
 167         if let ty::PredicateKind::Clause(ty::Clause::Trait(tpred)) = obligation.predicate.kind().skip_binder()
 168             && let Some(ty) = self.shallow_resolve(tpred.self_ty()).ty_vid().map(|t| self.root_var(t))
 169             && self.tcx.lang_items().sized_trait().map_or(false, |st| st != tpred.trait_ref.def_id)
 170         {
 171             let new_self_ty = self.tcx.types.unit;
 172
 173             // Then construct a new obligation with Self = () added
 174             // to the ParamEnv, and see if it holds.
 175             let o = obligation.with(self.tcx,
 176                 obligation
 177                     .predicate
 178                     .kind()
 179                     .rebind(
 180                         // (*) binder moved here
 181                         ty::PredicateKind::Clause(ty::Clause::Trait(tpred.with_self_ty(self.tcx, new_self_ty)))
 182                     ),
 183             );
 184             // Don't report overflow errors. Otherwise equivalent to may_hold.
 185             if let Ok(result) = self.probe(|_| self.evaluate_obligation(&o)) && result.may_apply() {
 186                 infer_var_info.entry(ty).or_default().self_in_trait = true;
 187             }
 188         }
 189
 190         if let ty::PredicateKind::Clause(ty::Clause::Projection(predicate)) =
 191             obligation.predicate.kind().skip_binder()
 192         {
 193             // If the projection predicate (Foo::Bar == X) has X as a non-TyVid,
 194             // we need to make it into one.
 195             if let Some(vid) = predicate.term.ty().and_then(|ty| ty.ty_vid()) {
 196                 debug!("infer_var_info: {:?}.output = true", vid);
 197                 infer_var_info.entry(vid).or_default().output = true;
 198             }
 199         }
 200     }
 201 }