compiler/rustc_typeck/src/check/inherited.rs

   1 use super::callee::DeferredCallResolution;
   2
   3 use rustc_data_structures::fx::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::{InferCtxt, InferOk, TyCtxtInferExt};
   9 use rustc_middle::ty::fold::TypeFoldable;
  10 use rustc_middle::ty::visit::TypeVisitable;
  11 use rustc_middle::ty::{self, Ty, TyCtxt};
  12 use rustc_span::def_id::LocalDefIdMap;
  13 use rustc_span::{self, Span};
  14 use rustc_trait_selection::infer::InferCtxtExt as _;
  15 use rustc_trait_selection::traits::{self, ObligationCause, TraitEngine, TraitEngineExt};
  16
  17 use std::cell::RefCell;
  18 use std::ops::Deref;
  19
  20 /// Closures defined within the function. For example:
  21 /// ```ignore (illustrative)
  22 /// fn foo() {
  23 ///     bar(move|| { ... })
  24 /// }
  25 /// ```
  26 /// Here, the function `foo()` and the closure passed to
  27 /// `bar()` will each have their own `FnCtxt`, but they will
  28 /// share the inherited fields.
  29 pub struct Inherited<'a, 'tcx> {
  30     pub(super) infcx: InferCtxt<'a, 'tcx>,
  31
  32     pub(super) typeck_results: &'a RefCell<ty::TypeckResults<'tcx>>,
  33
  34     pub(super) locals: RefCell<HirIdMap<super::LocalTy<'tcx>>>,
  35
  36     pub(super) fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
  37
  38     // Some additional `Sized` obligations badly affect type inference.
  39     // These obligations are added in a later stage of typeck.
  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>, Span)>>,
  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<(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
  69 impl<'a, 'tcx> Deref for Inherited<'a, 'tcx> {
  70     type Target = InferCtxt<'a, 'tcx>;
  71     fn deref(&self) -> &Self::Target {
  72         &self.infcx
  73     }
  74 }
  75
  76 /// A temporary returned by `Inherited::build(...)`. This is necessary
  77 /// for multiple `InferCtxt` to share the same `in_progress_typeck_results`
  78 /// without using `Rc` or something similar.
  79 pub struct InheritedBuilder<'tcx> {
  80     infcx: infer::InferCtxtBuilder<'tcx>,
  81     def_id: LocalDefId,
  82 }
  83
  84 impl<'tcx> Inherited<'_, 'tcx> {
  85     pub fn build(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> InheritedBuilder<'tcx> {
  86         let hir_owner = tcx.hir().local_def_id_to_hir_id(def_id).owner;
  87
  88         InheritedBuilder {
  89             infcx: tcx
  90                 .infer_ctxt()
  91                 .ignoring_regions()
  92                 .with_fresh_in_progress_typeck_results(hir_owner),
  93             def_id,
  94         }
  95     }
  96 }
  97
  98 impl<'tcx> InheritedBuilder<'tcx> {
  99     pub fn enter<F, R>(&mut self, f: F) -> R
 100     where
 101         F: for<'a> FnOnce(Inherited<'a, 'tcx>) -> R,
 102     {
 103         let def_id = self.def_id;
 104         self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
 105     }
 106 }
 107
 108 impl<'a, 'tcx> Inherited<'a, 'tcx> {
 109     fn new(infcx: InferCtxt<'a, 'tcx>, def_id: LocalDefId) -> Self {
 110         let tcx = infcx.tcx;
 111         let body_id = tcx.hir().maybe_body_owned_by(def_id);
 112         let typeck_results =
 113             infcx.in_progress_typeck_results.expect("building `FnCtxt` without typeck results");
 114
 115         Inherited {
 116             typeck_results,
 117             infcx,
 118             fulfillment_cx: RefCell::new(<dyn TraitEngine<'_>>::new(tcx)),
 119             locals: RefCell::new(Default::default()),
 120             deferred_sized_obligations: RefCell::new(Vec::new()),
 121             deferred_call_resolutions: RefCell::new(Default::default()),
 122             deferred_cast_checks: RefCell::new(Vec::new()),
 123             deferred_transmute_checks: RefCell::new(Vec::new()),
 124             deferred_asm_checks: RefCell::new(Vec::new()),
 125             deferred_generator_interiors: RefCell::new(Vec::new()),
 126             diverging_type_vars: RefCell::new(Default::default()),
 127             body_id,
 128         }
 129     }
 130
 131     #[instrument(level = "debug", skip(self))]
 132     pub(super) fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
 133         if obligation.has_escaping_bound_vars() {
 134             span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}", obligation);
 135         }
 136         self.fulfillment_cx.borrow_mut().register_predicate_obligation(self, obligation);
 137     }
 138
 139     pub(super) fn register_predicates<I>(&self, obligations: I)
 140     where
 141         I: IntoIterator<Item = traits::PredicateObligation<'tcx>>,
 142     {
 143         for obligation in obligations {
 144             self.register_predicate(obligation);
 145         }
 146     }
 147
 148     pub(super) fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
 149         self.register_predicates(infer_ok.obligations);
 150         infer_ok.value
 151     }
 152
 153     pub(super) fn normalize_associated_types_in<T>(
 154         &self,
 155         span: Span,
 156         body_id: hir::HirId,
 157         param_env: ty::ParamEnv<'tcx>,
 158         value: T,
 159     ) -> T
 160     where
 161         T: TypeFoldable<'tcx>,
 162     {
 163         self.normalize_associated_types_in_with_cause(
 164             ObligationCause::misc(span, body_id),
 165             param_env,
 166             value,
 167         )
 168     }
 169
 170     pub(super) fn normalize_associated_types_in_with_cause<T>(
 171         &self,
 172         cause: ObligationCause<'tcx>,
 173         param_env: ty::ParamEnv<'tcx>,
 174         value: T,
 175     ) -> T
 176     where
 177         T: TypeFoldable<'tcx>,
 178     {
 179         let ok = self.partially_normalize_associated_types_in(cause, param_env, value);
 180         debug!(?ok);
 181         self.register_infer_ok_obligations(ok)
 182     }
 183 }