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