compiler/rustc_hir_typeck/src/inherited.rs

   1 use super::callee::DeferredCallResolution;
   2
   3 use rustc_data_structures::fx::FxHashSet;
   4 use rustc_data_structures::sync::Lrc;
   5 use rustc_hir as hir;
   6 use rustc_hir::def_id::LocalDefId;
   7 use rustc_hir::HirIdMap;
   8 use rustc_infer::infer;
   9 use rustc_infer::infer::{DefiningAnchor, InferCtxt, InferOk, TyCtxtInferExt};
  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::traits::{
  15     self, ObligationCause, ObligationCtxt, TraitEngine, TraitEngineExt as _,
  16 };
  17
  18 use std::cell::RefCell;
  19 use std::ops::Deref;
  20
  21 /// Closures defined within the function. For example:
  22 /// ```ignore (illustrative)
  23 /// fn foo() {
  24 ///     bar(move|| { ... })
  25 /// }
  26 /// ```
  27 /// Here, the function `foo()` and the closure passed to
  28 /// `bar()` will each have their own `FnCtxt`, but they will
  29 /// share the inherited fields.
  30 pub struct Inherited<'tcx> {
  31     pub(super) infcx: InferCtxt<'tcx>,
  32
  33     pub(super) typeck_results: RefCell<ty::TypeckResults<'tcx>>,
  34
  35     pub(super) locals: RefCell<HirIdMap<super::LocalTy<'tcx>>>,
  36
  37     pub(super) fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
  38
  39     /// Some additional `Sized` obligations badly affect type inference.
  40     /// These obligations are added in a later stage of typeck.
  41     /// Removing these may also cause additional complications, see #101066.
  42     pub(super) deferred_sized_obligations:
  43         RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
  44
  45     /// When we process a call like `c()` where `c` is a closure type,
  46     /// we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
  47     /// `FnOnce` closure. In that case, we defer full resolution of the
  48     /// call until upvar inference can kick in and make the
  49     /// decision. We keep these deferred resolutions grouped by the
  50     /// def-id of the closure, so that once we decide, we can easily go
  51     /// back and process them.
  52     pub(super) deferred_call_resolutions: RefCell<LocalDefIdMap<Vec<DeferredCallResolution<'tcx>>>>,
  53
  54     pub(super) deferred_cast_checks: RefCell<Vec<super::cast::CastCheck<'tcx>>>,
  55
  56     pub(super) deferred_transmute_checks: RefCell<Vec<(Ty<'tcx>, Ty<'tcx>, hir::HirId)>>,
  57
  58     pub(super) deferred_asm_checks: RefCell<Vec<(&'tcx hir::InlineAsm<'tcx>, hir::HirId)>>,
  59
  60     pub(super) deferred_generator_interiors:
  61         RefCell<Vec<(hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
  62
  63     pub(super) body_id: Option<hir::BodyId>,
  64
  65     /// Whenever we introduce an adjustment from `!` into a type variable,
  66     /// we record that type variable here. This is later used to inform
  67     /// fallback. See the `fallback` module for details.
  68     pub(super) diverging_type_vars: RefCell<FxHashSet<Ty<'tcx>>>,
  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                 .with_normalize_fn_sig_for_diagnostic(Lrc::new(move |infcx, fn_sig| {
  97                     if fn_sig.has_escaping_bound_vars() {
  98                         return fn_sig;
  99                     }
 100                     infcx.probe(|_| {
 101                         let ocx = ObligationCtxt::new_in_snapshot(infcx);
 102                         let normalized_fn_sig = ocx.normalize(
 103                             &ObligationCause::dummy(),
 104                             // FIXME(compiler-errors): This is probably not the right param-env...
 105                             infcx.tcx.param_env(def_id),
 106                             fn_sig,
 107                         );
 108                         if ocx.select_all_or_error().is_empty() {
 109                             let normalized_fn_sig =
 110                                 infcx.resolve_vars_if_possible(normalized_fn_sig);
 111                             if !normalized_fn_sig.needs_infer() {
 112                                 return normalized_fn_sig;
 113                             }
 114                         }
 115                         fn_sig
 116                     })
 117                 })),
 118             def_id,
 119             typeck_results: RefCell::new(ty::TypeckResults::new(hir_owner)),
 120         }
 121     }
 122 }
 123
 124 impl<'tcx> InheritedBuilder<'tcx> {
 125     pub fn enter<F, R>(mut self, f: F) -> R
 126     where
 127         F: FnOnce(&Inherited<'tcx>) -> R,
 128     {
 129         let def_id = self.def_id;
 130         f(&Inherited::new(self.infcx.build(), def_id, self.typeck_results))
 131     }
 132 }
 133
 134 impl<'tcx> Inherited<'tcx> {
 135     fn new(
 136         infcx: InferCtxt<'tcx>,
 137         def_id: LocalDefId,
 138         typeck_results: RefCell<ty::TypeckResults<'tcx>>,
 139     ) -> Self {
 140         let tcx = infcx.tcx;
 141         let body_id = tcx.hir().maybe_body_owned_by(def_id);
 142
 143         Inherited {
 144             typeck_results,
 145             infcx,
 146             fulfillment_cx: RefCell::new(<dyn TraitEngine<'_>>::new(tcx)),
 147             locals: RefCell::new(Default::default()),
 148             deferred_sized_obligations: RefCell::new(Vec::new()),
 149             deferred_call_resolutions: RefCell::new(Default::default()),
 150             deferred_cast_checks: RefCell::new(Vec::new()),
 151             deferred_transmute_checks: RefCell::new(Vec::new()),
 152             deferred_asm_checks: RefCell::new(Vec::new()),
 153             deferred_generator_interiors: RefCell::new(Vec::new()),
 154             diverging_type_vars: RefCell::new(Default::default()),
 155             body_id,
 156         }
 157     }
 158
 159     #[instrument(level = "debug", skip(self))]
 160     pub(super) fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
 161         if obligation.has_escaping_bound_vars() {
 162             span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}", obligation);
 163         }
 164         self.fulfillment_cx.borrow_mut().register_predicate_obligation(self, obligation);
 165     }
 166
 167     pub(super) fn register_predicates<I>(&self, obligations: I)
 168     where
 169         I: IntoIterator<Item = traits::PredicateObligation<'tcx>>,
 170     {
 171         for obligation in obligations {
 172             self.register_predicate(obligation);
 173         }
 174     }
 175
 176     pub(super) fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
 177         self.register_predicates(infer_ok.obligations);
 178         infer_ok.value
 179     }
 180 }