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 /// ```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<'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_transmute_checks: RefCell<Vec<(Ty<'tcx>, Ty<'tcx>, Span)>>,
  54
  55     pub(super) deferred_asm_checks: RefCell<Vec<(&'tcx hir::InlineAsm<'tcx>, hir::HirId)>>,
  56
  57     pub(super) deferred_generator_interiors:
  58         RefCell<Vec<(hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
  59
  60     pub(super) body_id: Option<hir::BodyId>,
  61
  62     /// Whenever we introduce an adjustment from `!` into a type variable,
  63     /// we record that type variable here. This is later used to inform
  64     /// fallback. See the `fallback` module for details.
  65     pub(super) diverging_type_vars: RefCell<FxHashSet<Ty<'tcx>>>,
  66 }
  67
  68 impl<'a, 'tcx> Deref for Inherited<'a, 'tcx> {
  69     type Target = InferCtxt<'a, 'tcx>;
  70     fn deref(&self) -> &Self::Target {
  71         &self.infcx
  72     }
  73 }
  74
  75 /// A temporary returned by `Inherited::build(...)`. This is necessary
  76 /// for multiple `InferCtxt` to share the same `in_progress_typeck_results`
  77 /// without using `Rc` or something similar.
  78 pub struct InheritedBuilder<'tcx> {
  79     infcx: infer::InferCtxtBuilder<'tcx>,
  80     def_id: LocalDefId,
  81 }
  82
  83 impl<'tcx> Inherited<'_, 'tcx> {
  84     pub fn build(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> InheritedBuilder<'tcx> {
  85         let hir_owner = tcx.hir().local_def_id_to_hir_id(def_id).owner;
  86
  87         InheritedBuilder {
  88             infcx: tcx.infer_ctxt().with_fresh_in_progress_typeck_results(hir_owner),
  89             def_id,
  90         }
  91     }
  92 }
  93
  94 impl<'tcx> InheritedBuilder<'tcx> {
  95     pub fn enter<F, R>(&mut self, f: F) -> R
  96     where
  97         F: for<'a> FnOnce(Inherited<'a, 'tcx>) -> R,
  98     {
  99         let def_id = self.def_id;
 100         self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
 101     }
 102 }
 103
 104 impl<'a, 'tcx> Inherited<'a, 'tcx> {
 105     pub(super) fn new(infcx: InferCtxt<'a, 'tcx>, def_id: LocalDefId) -> Self {
 106         let tcx = infcx.tcx;
 107         let item_id = tcx.hir().local_def_id_to_hir_id(def_id);
 108         let body_id = tcx.hir().maybe_body_owned_by(item_id);
 109
 110         Inherited {
 111             typeck_results: MaybeInProgressTables {
 112                 maybe_typeck_results: infcx.in_progress_typeck_results,
 113             },
 114             infcx,
 115             fulfillment_cx: RefCell::new(<dyn TraitEngine<'_>>::new(tcx)),
 116             locals: RefCell::new(Default::default()),
 117             deferred_sized_obligations: RefCell::new(Vec::new()),
 118             deferred_call_resolutions: RefCell::new(Default::default()),
 119             deferred_cast_checks: RefCell::new(Vec::new()),
 120             deferred_transmute_checks: RefCell::new(Vec::new()),
 121             deferred_asm_checks: RefCell::new(Vec::new()),
 122             deferred_generator_interiors: RefCell::new(Vec::new()),
 123             diverging_type_vars: RefCell::new(Default::default()),
 124             body_id,
 125         }
 126     }
 127
 128     #[instrument(level = "debug", skip(self))]
 129     pub(super) fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
 130         if obligation.has_escaping_bound_vars() {
 131             span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}", obligation);
 132         }
 133         self.fulfillment_cx.borrow_mut().register_predicate_obligation(self, obligation);
 134     }
 135
 136     pub(super) fn register_predicates<I>(&self, obligations: I)
 137     where
 138         I: IntoIterator<Item = traits::PredicateObligation<'tcx>>,
 139     {
 140         for obligation in obligations {
 141             self.register_predicate(obligation);
 142         }
 143     }
 144
 145     pub(super) fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
 146         self.register_predicates(infer_ok.obligations);
 147         infer_ok.value
 148     }
 149
 150     pub(super) fn normalize_associated_types_in<T>(
 151         &self,
 152         span: Span,
 153         body_id: hir::HirId,
 154         param_env: ty::ParamEnv<'tcx>,
 155         value: T,
 156     ) -> T
 157     where
 158         T: TypeFoldable<'tcx>,
 159     {
 160         self.normalize_associated_types_in_with_cause(
 161             ObligationCause::misc(span, body_id),
 162             param_env,
 163             value,
 164         )
 165     }
 166
 167     pub(super) fn normalize_associated_types_in_with_cause<T>(
 168         &self,
 169         cause: ObligationCause<'tcx>,
 170         param_env: ty::ParamEnv<'tcx>,
 171         value: T,
 172     ) -> T
 173     where
 174         T: TypeFoldable<'tcx>,
 175     {
 176         let ok = self.partially_normalize_associated_types_in(cause, param_env, value);
 177         debug!(?ok);
 178         self.register_infer_ok_obligations(ok)
 179     }
 180 }