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     // When we process a call like `c()` where `c` is a closure type,
  39     // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
  40     // `FnOnce` closure. In that case, we defer full resolution of the
  41     // call until upvar inference can kick in and make the
  42     // decision. We keep these deferred resolutions grouped by the
  43     // def-id of the closure, so that once we decide, we can easily go
  44     // back and process them.
  45     pub(super) deferred_call_resolutions: RefCell<LocalDefIdMap<Vec<DeferredCallResolution<'tcx>>>>,
  46
  47     pub(super) deferred_cast_checks: RefCell<Vec<super::cast::CastCheck<'tcx>>>,
  48
  49     pub(super) deferred_transmute_checks: RefCell<Vec<(Ty<'tcx>, Ty<'tcx>, Span)>>,
  50
  51     pub(super) deferred_asm_checks: RefCell<Vec<(&'tcx hir::InlineAsm<'tcx>, hir::HirId)>>,
  52
  53     pub(super) deferred_generator_interiors:
  54         RefCell<Vec<(hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
  55
  56     pub(super) body_id: Option<hir::BodyId>,
  57
  58     /// Whenever we introduce an adjustment from `!` into a type variable,
  59     /// we record that type variable here. This is later used to inform
  60     /// fallback. See the `fallback` module for details.
  61     pub(super) diverging_type_vars: RefCell<FxHashSet<Ty<'tcx>>>,
  62 }
  63
  64 impl<'a, 'tcx> Deref for Inherited<'a, 'tcx> {
  65     type Target = InferCtxt<'a, 'tcx>;
  66     fn deref(&self) -> &Self::Target {
  67         &self.infcx
  68     }
  69 }
  70
  71 /// A temporary returned by `Inherited::build(...)`. This is necessary
  72 /// for multiple `InferCtxt` to share the same `in_progress_typeck_results`
  73 /// without using `Rc` or something similar.
  74 pub struct InheritedBuilder<'tcx> {
  75     infcx: infer::InferCtxtBuilder<'tcx>,
  76     def_id: LocalDefId,
  77 }
  78
  79 impl<'tcx> Inherited<'_, 'tcx> {
  80     pub fn build(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> InheritedBuilder<'tcx> {
  81         let hir_owner = tcx.hir().local_def_id_to_hir_id(def_id).owner;
  82
  83         InheritedBuilder {
  84             infcx: tcx
  85                 .infer_ctxt()
  86                 .ignoring_regions()
  87                 .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<'a, 'tcx> Inherited<'a, 'tcx> {
 104     fn new(infcx: InferCtxt<'a, 'tcx>, def_id: LocalDefId) -> Self {
 105         let tcx = infcx.tcx;
 106         let body_id = tcx.hir().maybe_body_owned_by(def_id);
 107         let typeck_results =
 108             infcx.in_progress_typeck_results.expect("building `FnCtxt` without typeck results");
 109
 110         Inherited {
 111             typeck_results,
 112             infcx,
 113             fulfillment_cx: RefCell::new(<dyn TraitEngine<'_>>::new(tcx)),
 114             locals: RefCell::new(Default::default()),
 115             deferred_call_resolutions: RefCell::new(Default::default()),
 116             deferred_cast_checks: RefCell::new(Vec::new()),
 117             deferred_transmute_checks: RefCell::new(Vec::new()),
 118             deferred_asm_checks: RefCell::new(Vec::new()),
 119             deferred_generator_interiors: RefCell::new(Vec::new()),
 120             diverging_type_vars: RefCell::new(Default::default()),
 121             body_id,
 122         }
 123     }
 124
 125     #[instrument(level = "debug", skip(self))]
 126     pub(super) fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
 127         if obligation.has_escaping_bound_vars() {
 128             span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}", obligation);
 129         }
 130         self.fulfillment_cx.borrow_mut().register_predicate_obligation(self, obligation);
 131     }
 132
 133     pub(super) fn register_predicates<I>(&self, obligations: I)
 134     where
 135         I: IntoIterator<Item = traits::PredicateObligation<'tcx>>,
 136     {
 137         for obligation in obligations {
 138             self.register_predicate(obligation);
 139         }
 140     }
 141
 142     pub(super) fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
 143         self.register_predicates(infer_ok.obligations);
 144         infer_ok.value
 145     }
 146
 147     pub(super) fn normalize_associated_types_in<T>(
 148         &self,
 149         span: Span,
 150         body_id: hir::HirId,
 151         param_env: ty::ParamEnv<'tcx>,
 152         value: T,
 153     ) -> T
 154     where
 155         T: TypeFoldable<'tcx>,
 156     {
 157         self.normalize_associated_types_in_with_cause(
 158             ObligationCause::misc(span, body_id),
 159             param_env,
 160             value,
 161         )
 162     }
 163
 164     pub(super) fn normalize_associated_types_in_with_cause<T>(
 165         &self,
 166         cause: ObligationCause<'tcx>,
 167         param_env: ty::ParamEnv<'tcx>,
 168         value: T,
 169     ) -> T
 170     where
 171         T: TypeFoldable<'tcx>,
 172     {
 173         let ok = self.partially_normalize_associated_types_in(cause, param_env, value);
 174         debug!(?ok);
 175         self.register_infer_ok_obligations(ok)
 176     }
 177 }