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::fold::TypeFoldable;
  11 use rustc_middle::ty::visit::TypeVisitable;
  12 use rustc_middle::ty::{self, Ty, TyCtxt};
  13 use rustc_span::def_id::LocalDefIdMap;
  14 use rustc_span::{self, Span};
  15 use rustc_trait_selection::infer::InferCtxtExt as _;
  16 use rustc_trait_selection::traits::{
  17     self, ObligationCause, ObligationCtxt, TraitEngine, TraitEngineExt as _,
  18 };
  19
  20 use std::cell::RefCell;
  21 use std::ops::Deref;
  22
  23 /// Closures defined within the function. For example:
  24 /// ```ignore (illustrative)
  25 /// fn foo() {
  26 ///     bar(move|| { ... })
  27 /// }
  28 /// ```
  29 /// Here, the function `foo()` and the closure passed to
  30 /// `bar()` will each have their own `FnCtxt`, but they will
  31 /// share the inherited fields.
  32 pub struct Inherited<'tcx> {
  33     pub(super) infcx: InferCtxt<'tcx>,
  34
  35     pub(super) typeck_results: RefCell<ty::TypeckResults<'tcx>>,
  36
  37     pub(super) locals: RefCell<HirIdMap<super::LocalTy<'tcx>>>,
  38
  39     pub(super) fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
  40
  41     // Some additional `Sized` obligations badly affect type inference.
  42     // These obligations are added in a later stage of typeck.
  43     // Removing these may also cause additional complications, see #101066.
  44     pub(super) deferred_sized_obligations:
  45         RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
  46
  47     // When we process a call like `c()` where `c` is a closure type,
  48     // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
  49     // `FnOnce` closure. In that case, we defer full resolution of the
  50     // call until upvar inference can kick in and make the
  51     // decision. We keep these deferred resolutions grouped by the
  52     // def-id of the closure, so that once we decide, we can easily go
  53     // back and process them.
  54     pub(super) deferred_call_resolutions: RefCell<LocalDefIdMap<Vec<DeferredCallResolution<'tcx>>>>,
  55
  56     pub(super) deferred_cast_checks: RefCell<Vec<super::cast::CastCheck<'tcx>>>,
  57
  58     pub(super) deferred_transmute_checks: RefCell<Vec<(Ty<'tcx>, Ty<'tcx>, hir::HirId)>>,
  59
  60     pub(super) deferred_asm_checks: RefCell<Vec<(&'tcx hir::InlineAsm<'tcx>, hir::HirId)>>,
  61
  62     pub(super) deferred_generator_interiors:
  63         RefCell<Vec<(hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
  64
  65     pub(super) body_id: Option<hir::BodyId>,
  66
  67     /// Whenever we introduce an adjustment from `!` into a type variable,
  68     /// we record that type variable here. This is later used to inform
  69     /// fallback. See the `fallback` module for details.
  70     pub(super) diverging_type_vars: RefCell<FxHashSet<Ty<'tcx>>>,
  71 }
  72
  73 impl<'tcx> Deref for Inherited<'tcx> {
  74     type Target = InferCtxt<'tcx>;
  75     fn deref(&self) -> &Self::Target {
  76         &self.infcx
  77     }
  78 }
  79
  80 /// A temporary returned by `Inherited::build(...)`. This is necessary
  81 /// for multiple `InferCtxt` to share the same `typeck_results`
  82 /// without using `Rc` or something similar.
  83 pub struct InheritedBuilder<'tcx> {
  84     infcx: infer::InferCtxtBuilder<'tcx>,
  85     def_id: LocalDefId,
  86     typeck_results: RefCell<ty::TypeckResults<'tcx>>,
  87 }
  88
  89 impl<'tcx> Inherited<'tcx> {
  90     pub fn build(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> InheritedBuilder<'tcx> {
  91         let hir_owner = tcx.hir().local_def_id_to_hir_id(def_id).owner;
  92
  93         InheritedBuilder {
  94             infcx: tcx
  95                 .infer_ctxt()
  96                 .ignoring_regions()
  97                 .with_opaque_type_inference(DefiningAnchor::Bind(hir_owner.def_id))
  98                 .with_normalize_fn_sig_for_diagnostic(Lrc::new(move |infcx, fn_sig| {
  99                     if fn_sig.has_escaping_bound_vars() {
 100                         return fn_sig;
 101                     }
 102                     infcx.probe(|_| {
 103                         let ocx = ObligationCtxt::new_in_snapshot(infcx);
 104                         let normalized_fn_sig = ocx.normalize(
 105                             ObligationCause::dummy(),
 106                             // FIXME(compiler-errors): This is probably not the right param-env...
 107                             infcx.tcx.param_env(def_id),
 108                             fn_sig,
 109                         );
 110                         if ocx.select_all_or_error().is_empty() {
 111                             let normalized_fn_sig =
 112                                 infcx.resolve_vars_if_possible(normalized_fn_sig);
 113                             if !normalized_fn_sig.needs_infer() {
 114                                 return normalized_fn_sig;
 115                             }
 116                         }
 117                         fn_sig
 118                     })
 119                 })),
 120             def_id,
 121             typeck_results: RefCell::new(ty::TypeckResults::new(hir_owner)),
 122         }
 123     }
 124 }
 125
 126 impl<'tcx> InheritedBuilder<'tcx> {
 127     pub fn enter<F, R>(mut self, f: F) -> R
 128     where
 129         F: FnOnce(&Inherited<'tcx>) -> R,
 130     {
 131         let def_id = self.def_id;
 132         f(&Inherited::new(self.infcx.build(), def_id, self.typeck_results))
 133     }
 134 }
 135
 136 impl<'tcx> Inherited<'tcx> {
 137     fn new(
 138         infcx: InferCtxt<'tcx>,
 139         def_id: LocalDefId,
 140         typeck_results: RefCell<ty::TypeckResults<'tcx>>,
 141     ) -> Self {
 142         let tcx = infcx.tcx;
 143         let body_id = tcx.hir().maybe_body_owned_by(def_id);
 144
 145         Inherited {
 146             typeck_results,
 147             infcx,
 148             fulfillment_cx: RefCell::new(<dyn TraitEngine<'_>>::new(tcx)),
 149             locals: RefCell::new(Default::default()),
 150             deferred_sized_obligations: RefCell::new(Vec::new()),
 151             deferred_call_resolutions: RefCell::new(Default::default()),
 152             deferred_cast_checks: RefCell::new(Vec::new()),
 153             deferred_transmute_checks: RefCell::new(Vec::new()),
 154             deferred_asm_checks: RefCell::new(Vec::new()),
 155             deferred_generator_interiors: RefCell::new(Vec::new()),
 156             diverging_type_vars: RefCell::new(Default::default()),
 157             body_id,
 158         }
 159     }
 160
 161     #[instrument(level = "debug", skip(self))]
 162     pub(super) fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
 163         if obligation.has_escaping_bound_vars() {
 164             span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}", obligation);
 165         }
 166         self.fulfillment_cx.borrow_mut().register_predicate_obligation(self, obligation);
 167     }
 168
 169     pub(super) fn register_predicates<I>(&self, obligations: I)
 170     where
 171         I: IntoIterator<Item = traits::PredicateObligation<'tcx>>,
 172     {
 173         for obligation in obligations {
 174             self.register_predicate(obligation);
 175         }
 176     }
 177
 178     pub(super) fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
 179         self.register_predicates(infer_ok.obligations);
 180         infer_ok.value
 181     }
 182
 183     pub(super) fn normalize_associated_types_in<T>(
 184         &self,
 185         span: Span,
 186         body_id: hir::HirId,
 187         param_env: ty::ParamEnv<'tcx>,
 188         value: T,
 189     ) -> T
 190     where
 191         T: TypeFoldable<'tcx>,
 192     {
 193         self.normalize_associated_types_in_with_cause(
 194             ObligationCause::misc(span, body_id),
 195             param_env,
 196             value,
 197         )
 198     }
 199
 200     pub(super) fn normalize_associated_types_in_with_cause<T>(
 201         &self,
 202         cause: ObligationCause<'tcx>,
 203         param_env: ty::ParamEnv<'tcx>,
 204         value: T,
 205     ) -> T
 206     where
 207         T: TypeFoldable<'tcx>,
 208     {
 209         let ok = self.partially_normalize_associated_types_in(cause, param_env, value);
 210         debug!(?ok);
 211         self.register_infer_ok_obligations(ok)
 212     }
 213 }