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