compiler/rustc_typeck/src/check/inherited.rs

   1 use super::callee::DeferredCallResolution;
   2 use super::MaybeInProgressTables;
   3
   4 use rustc_hir as hir;
   5 use rustc_hir::def_id::{DefIdMap, LocalDefId};
   6 use rustc_hir::HirIdMap;
   7 use rustc_infer::infer;
   8 use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
   9 use rustc_middle::ty::fold::TypeFoldable;
  10 use rustc_middle::ty::{self, Ty, TyCtxt};
  11 use rustc_span::{self, Span};
  12 use rustc_trait_selection::infer::InferCtxtExt as _;
  13 use rustc_trait_selection::traits::{self, ObligationCause, TraitEngine, TraitEngineExt};
  14
  15 use std::cell::RefCell;
  16 use std::ops::Deref;
  17
  18 /// Closures defined within the function. For example:
  19 ///
  20 ///     fn foo() {
  21 ///         bar(move|| { ... })
  22 ///     }
  23 ///
  24 /// Here, the function `foo()` and the closure passed to
  25 /// `bar()` will each have their own `FnCtxt`, but they will
  26 /// share the inherited fields.
  27 pub struct Inherited<'a, 'tcx> {
  28     pub(super) infcx: InferCtxt<'a, 'tcx>,
  29
  30     pub(super) typeck_results: super::MaybeInProgressTables<'a, 'tcx>,
  31
  32     pub(super) locals: RefCell<HirIdMap<super::LocalTy<'tcx>>>,
  33
  34     pub(super) fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
  35
  36     // Some additional `Sized` obligations badly affect type inference.
  37     // These obligations are added in a later stage of typeck.
  38     pub(super) deferred_sized_obligations:
  39         RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
  40
  41     // When we process a call like `c()` where `c` is a closure type,
  42     // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
  43     // `FnOnce` closure. In that case, we defer full resolution of the
  44     // call until upvar inference can kick in and make the
  45     // decision. We keep these deferred resolutions grouped by the
  46     // def-id of the closure, so that once we decide, we can easily go
  47     // back and process them.
  48     pub(super) deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'tcx>>>>,
  49
  50     pub(super) deferred_cast_checks: RefCell<Vec<super::cast::CastCheck<'tcx>>>,
  51
  52     pub(super) deferred_generator_interiors:
  53         RefCell<Vec<(hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
  54
  55     /// Reports whether this is in a const context.
  56     pub(super) constness: hir::Constness,
  57
  58     pub(super) body_id: Option<hir::BodyId>,
  59 }
  60
  61 impl<'a, 'tcx> Deref for Inherited<'a, 'tcx> {
  62     type Target = InferCtxt<'a, 'tcx>;
  63     fn deref(&self) -> &Self::Target {
  64         &self.infcx
  65     }
  66 }
  67
  68 /// Helper type of a temporary returned by `Inherited::build(...)`.
  69 /// Necessary because we can't write the following bound:
  70 /// `F: for<'b, 'tcx> where 'tcx FnOnce(Inherited<'b, 'tcx>)`.
  71 pub struct InheritedBuilder<'tcx> {
  72     infcx: infer::InferCtxtBuilder<'tcx>,
  73     def_id: LocalDefId,
  74 }
  75
  76 impl Inherited<'_, 'tcx> {
  77     pub fn build(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> InheritedBuilder<'tcx> {
  78         let hir_owner = tcx.hir().local_def_id_to_hir_id(def_id).owner;
  79
  80         InheritedBuilder {
  81             infcx: tcx.infer_ctxt().with_fresh_in_progress_typeck_results(hir_owner),
  82             def_id,
  83         }
  84     }
  85 }
  86
  87 impl<'tcx> InheritedBuilder<'tcx> {
  88     pub fn enter<F, R>(&mut self, f: F) -> R
  89     where
  90         F: for<'a> FnOnce(Inherited<'a, 'tcx>) -> R,
  91     {
  92         let def_id = self.def_id;
  93         self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
  94     }
  95 }
  96
  97 impl Inherited<'a, 'tcx> {
  98     pub(super) fn new(infcx: InferCtxt<'a, 'tcx>, def_id: LocalDefId) -> Self {
  99         let tcx = infcx.tcx;
 100         let item_id = tcx.hir().local_def_id_to_hir_id(def_id);
 101         Self::with_constness(infcx, def_id, tcx.hir().get(item_id).constness())
 102     }
 103
 104     pub(super) fn with_constness(infcx: InferCtxt<'a, 'tcx>, def_id: LocalDefId, constness: hir::Constness) -> Self {
 105         let tcx = infcx.tcx;
 106         let item_id = tcx.hir().local_def_id_to_hir_id(def_id);
 107         let body_id = tcx.hir().maybe_body_owned_by(item_id);
 108
 109         Inherited {
 110             typeck_results: MaybeInProgressTables {
 111                 maybe_typeck_results: infcx.in_progress_typeck_results,
 112             },
 113             infcx,
 114             fulfillment_cx: RefCell::new(<dyn TraitEngine<'_>>::new(tcx)),
 115             locals: RefCell::new(Default::default()),
 116             deferred_sized_obligations: RefCell::new(Vec::new()),
 117             deferred_call_resolutions: RefCell::new(Default::default()),
 118             deferred_cast_checks: RefCell::new(Vec::new()),
 119             deferred_generator_interiors: RefCell::new(Vec::new()),
 120             constness,
 121             body_id,
 122         }
 123     }
 124
 125     #[instrument(level = "debug", skip(self))]
 126     fn transform_predicate(&self, p: &mut ty::Predicate<'tcx>) {
 127         // Don't transform non-const bounds into const bounds,
 128         // but transform const bounds to non-const when we are
 129         // not in a const context.
 130         if let hir::Constness::NotConst = self.constness {
 131             let kind = p.kind();
 132             if let ty::PredicateKind::Trait(pred) = kind.as_ref().skip_binder() {
 133                 let mut pred = *pred;
 134                 pred.constness = hir::Constness::NotConst;
 135                 *p = kind.rebind(ty::PredicateKind::Trait(pred)).to_predicate(self.tcx);
 136             }
 137         }
 138     }
 139
 140     pub(super) fn register_predicate(&self, mut obligation: traits::PredicateObligation<'tcx>) {
 141         debug!("register_predicate({:?})", obligation);
 142         self.transform_predicate(&mut obligation.predicate);
 143         if obligation.has_escaping_bound_vars() {
 144             span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}", 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(super) fn normalize_associated_types_in<T>(
 164         &self,
 165         span: Span,
 166         body_id: hir::HirId,
 167         param_env: ty::ParamEnv<'tcx>,
 168         value: T,
 169     ) -> T
 170     where
 171         T: TypeFoldable<'tcx>,
 172     {
 173         self.normalize_associated_types_in_with_cause(
 174             ObligationCause::misc(span, body_id),
 175             param_env,
 176             value,
 177         )
 178     }
 179
 180     pub(super) fn normalize_associated_types_in_with_cause<T>(
 181         &self,
 182         cause: ObligationCause<'tcx>,
 183         param_env: ty::ParamEnv<'tcx>,
 184         value: T,
 185     ) -> T
 186     where
 187         T: TypeFoldable<'tcx>,
 188     {
 189         let ok = self.partially_normalize_associated_types_in(cause, param_env, value);
 190         debug!(?ok);
 191         self.register_infer_ok_obligations(ok)
 192     }
 193 }