1 files changed, 209 insertions, 0 deletions
diff --git a/compiler/rustc_hir_analysis/src/check/inherited.rs b/compiler/rustc_hir_analysis/src/check/inherited.rs
new file mode 100644
index 00000000000..37c830d4e38
--- /dev/null
+++ b/compiler/rustc_hir_analysis/src/check/inherited.rs
@@ -0,0 +1,209 @@
+use super::callee::DeferredCallResolution;
+
+use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::sync::Lrc;
+use rustc_hir as hir;
+use rustc_hir::def_id::LocalDefId;
+use rustc_hir::HirIdMap;
+use rustc_infer::infer;
+use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
+use rustc_middle::ty::fold::TypeFoldable;
+use rustc_middle::ty::visit::TypeVisitable;
+use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_span::def_id::LocalDefIdMap;
+use rustc_span::{self, Span};
+use rustc_trait_selection::infer::InferCtxtExt as _;
+use rustc_trait_selection::traits::{
+    self, ObligationCause, ObligationCtxt, TraitEngine, TraitEngineExt as _,
+};
+
+use std::cell::RefCell;
+use std::ops::Deref;
+
+/// Closures defined within the function. For example:
+/// ```ignore (illustrative)
+/// fn foo() {
+///     bar(move|| { ... })
+/// }
+/// ```
+/// Here, the function `foo()` and the closure passed to
+/// `bar()` will each have their own `FnCtxt`, but they will
+/// share the inherited fields.
+pub struct Inherited<'a, 'tcx> {
+    pub(super) infcx: InferCtxt<'a, 'tcx>,
+
+    pub(super) typeck_results: &'a RefCell<ty::TypeckResults<'tcx>>,
+
+    pub(super) locals: RefCell<HirIdMap<super::LocalTy<'tcx>>>,
+
+    pub(super) fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
+
+    // Some additional `Sized` obligations badly affect type inference.
+    // These obligations are added in a later stage of typeck.
+    // Removing these may also cause additional complications, see #101066.
+    pub(super) deferred_sized_obligations:
+        RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
+
+    // When we process a call like `c()` where `c` is a closure type,
+    // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
+    // `FnOnce` closure. In that case, we defer full resolution of the
+    // call until upvar inference can kick in and make the
+    // decision. We keep these deferred resolutions grouped by the
+    // def-id of the closure, so that once we decide, we can easily go
+    // back and process them.
+    pub(super) deferred_call_resolutions: RefCell<LocalDefIdMap<Vec<DeferredCallResolution<'tcx>>>>,
+
+    pub(super) deferred_cast_checks: RefCell<Vec<super::cast::CastCheck<'tcx>>>,
+
+    pub(super) deferred_transmute_checks: RefCell<Vec<(Ty<'tcx>, Ty<'tcx>, Span)>>,
+
+    pub(super) deferred_asm_checks: RefCell<Vec<(&'tcx hir::InlineAsm<'tcx>, hir::HirId)>>,
+
+    pub(super) deferred_generator_interiors:
+        RefCell<Vec<(hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
+
+    pub(super) body_id: Option<hir::BodyId>,
+
+    /// Whenever we introduce an adjustment from `!` into a type variable,
+    /// we record that type variable here. This is later used to inform
+    /// fallback. See the `fallback` module for details.
+    pub(super) diverging_type_vars: RefCell<FxHashSet<Ty<'tcx>>>,
+}
+
+impl<'a, 'tcx> Deref for Inherited<'a, 'tcx> {
+    type Target = InferCtxt<'a, 'tcx>;
+    fn deref(&self) -> &Self::Target {
+        &self.infcx
+    }
+}
+
+/// A temporary returned by `Inherited::build(...)`. This is necessary
+/// for multiple `InferCtxt` to share the same `in_progress_typeck_results`
+/// without using `Rc` or something similar.
+pub struct InheritedBuilder<'tcx> {
+    infcx: infer::InferCtxtBuilder<'tcx>,
+    def_id: LocalDefId,
+}
+
+impl<'tcx> Inherited<'_, 'tcx> {
+    pub fn build(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> InheritedBuilder<'tcx> {
+        let hir_owner = tcx.hir().local_def_id_to_hir_id(def_id).owner;
+
+        InheritedBuilder {
+            infcx: tcx
+                .infer_ctxt()
+                .ignoring_regions()
+                .with_fresh_in_progress_typeck_results(hir_owner)
+                .with_normalize_fn_sig_for_diagnostic(Lrc::new(move |infcx, fn_sig| {
+                    if fn_sig.has_escaping_bound_vars() {
+                        return fn_sig;
+                    }
+                    infcx.probe(|_| {
+                        let ocx = ObligationCtxt::new_in_snapshot(infcx);
+                        let normalized_fn_sig = ocx.normalize(
+                            ObligationCause::dummy(),
+                            // FIXME(compiler-errors): This is probably not the right param-env...
+                            infcx.tcx.param_env(def_id),
+                            fn_sig,
+                        );
+                        if ocx.select_all_or_error().is_empty() {
+                            let normalized_fn_sig =
+                                infcx.resolve_vars_if_possible(normalized_fn_sig);
+                            if !normalized_fn_sig.needs_infer() {
+                                return normalized_fn_sig;
+                            }
+                        }
+                        fn_sig
+                    })
+                })),
+            def_id,
+        }
+    }
+}
+
+impl<'tcx> InheritedBuilder<'tcx> {
+    pub fn enter<F, R>(&mut self, f: F) -> R
+    where
+        F: for<'a> FnOnce(Inherited<'a, 'tcx>) -> R,
+    {
+        let def_id = self.def_id;
+        self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
+    }
+}
+
+impl<'a, 'tcx> Inherited<'a, 'tcx> {
+    fn new(infcx: InferCtxt<'a, 'tcx>, def_id: LocalDefId) -> Self {
+        let tcx = infcx.tcx;
+        let body_id = tcx.hir().maybe_body_owned_by(def_id);
+        let typeck_results =
+            infcx.in_progress_typeck_results.expect("building `FnCtxt` without typeck results");
+
+        Inherited {
+            typeck_results,
+            infcx,
+            fulfillment_cx: RefCell::new(<dyn TraitEngine<'_>>::new(tcx)),
+            locals: RefCell::new(Default::default()),
+            deferred_sized_obligations: RefCell::new(Vec::new()),
+            deferred_call_resolutions: RefCell::new(Default::default()),
+            deferred_cast_checks: RefCell::new(Vec::new()),
+            deferred_transmute_checks: RefCell::new(Vec::new()),
+            deferred_asm_checks: RefCell::new(Vec::new()),
+            deferred_generator_interiors: RefCell::new(Vec::new()),
+            diverging_type_vars: RefCell::new(Default::default()),
+            body_id,
+        }
+    }
+
+    #[instrument(level = "debug", skip(self))]
+    pub(super) fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
+        if obligation.has_escaping_bound_vars() {
+            span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}", obligation);
+        }
+        self.fulfillment_cx.borrow_mut().register_predicate_obligation(self, obligation);
+    }
+
+    pub(super) fn register_predicates<I>(&self, obligations: I)
+    where
+        I: IntoIterator<Item = traits::PredicateObligation<'tcx>>,
+    {
+        for obligation in obligations {
+            self.register_predicate(obligation);
+        }
+    }
+
+    pub(super) fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
+        self.register_predicates(infer_ok.obligations);
+        infer_ok.value
+    }
+
+    pub(super) fn normalize_associated_types_in<T>(
+        &self,
+        span: Span,
+        body_id: hir::HirId,
+        param_env: ty::ParamEnv<'tcx>,
+        value: T,
+    ) -> T
+    where
+        T: TypeFoldable<'tcx>,
+    {
+        self.normalize_associated_types_in_with_cause(
+            ObligationCause::misc(span, body_id),
+            param_env,
+            value,
+        )
+    }
+
+    pub(super) fn normalize_associated_types_in_with_cause<T>(
+        &self,
+        cause: ObligationCause<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        value: T,
+    ) -> T
+    where
+        T: TypeFoldable<'tcx>,
+    {
+        let ok = self.partially_normalize_associated_types_in(cause, param_env, value);
+        debug!(?ok);
+        self.register_infer_ok_obligations(ok)
+    }
+}