1 files changed, 177 insertions, 0 deletions
diff --git a/compiler/rustc_trait_selection/src/infer.rs b/compiler/rustc_trait_selection/src/infer.rs
new file mode 100644
index 000000000..9d30374f8
--- /dev/null
+++ b/compiler/rustc_trait_selection/src/infer.rs
@@ -0,0 +1,177 @@
+use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
+use crate::traits::{self, TraitEngine, TraitEngineExt};
+
+use rustc_hir::def_id::DefId;
+use rustc_hir::lang_items::LangItem;
+use rustc_infer::traits::ObligationCause;
+use rustc_middle::arena::ArenaAllocatable;
+use rustc_middle::infer::canonical::{Canonical, CanonicalizedQueryResponse, QueryResponse};
+use rustc_middle::traits::query::Fallible;
+use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::ToPredicate;
+use rustc_middle::ty::{self, Ty, TypeFoldable, TypeVisitable};
+use rustc_span::{Span, DUMMY_SP};
+
+use std::fmt::Debug;
+
+pub use rustc_infer::infer::*;
+
+pub trait InferCtxtExt<'tcx> {
+    fn type_is_copy_modulo_regions(
+        &self,
+        param_env: ty::ParamEnv<'tcx>,
+        ty: Ty<'tcx>,
+        span: Span,
+    ) -> bool;
+
+    fn partially_normalize_associated_types_in<T>(
+        &self,
+        cause: ObligationCause<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        value: T,
+    ) -> InferOk<'tcx, T>
+    where
+        T: TypeFoldable<'tcx>;
+
+    /// Check whether a `ty` implements given trait(trait_def_id).
+    /// The inputs are:
+    ///
+    /// - the def-id of the trait
+    /// - the self type
+    /// - the *other* type parameters of the trait, excluding the self-type
+    /// - the parameter environment
+    ///
+    /// Invokes `evaluate_obligation`, so in the event that evaluating
+    /// `Ty: Trait` causes overflow, EvaluatedToRecur (or EvaluatedToUnknown)
+    /// will be returned.
+    fn type_implements_trait(
+        &self,
+        trait_def_id: DefId,
+        ty: Ty<'tcx>,
+        params: SubstsRef<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+    ) -> traits::EvaluationResult;
+}
+impl<'cx, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'cx, 'tcx> {
+    fn type_is_copy_modulo_regions(
+        &self,
+        param_env: ty::ParamEnv<'tcx>,
+        ty: Ty<'tcx>,
+        span: Span,
+    ) -> bool {
+        let ty = self.resolve_vars_if_possible(ty);
+
+        if !(param_env, ty).needs_infer() {
+            return ty.is_copy_modulo_regions(self.tcx.at(span), param_env);
+        }
+
+        let copy_def_id = self.tcx.require_lang_item(LangItem::Copy, None);
+
+        // This can get called from typeck (by euv), and `moves_by_default`
+        // rightly refuses to work with inference variables, but
+        // moves_by_default has a cache, which we want to use in other
+        // cases.
+        traits::type_known_to_meet_bound_modulo_regions(self, param_env, ty, copy_def_id, span)
+    }
+
+    /// Normalizes associated types in `value`, potentially returning
+    /// new obligations that must further be processed.
+    fn partially_normalize_associated_types_in<T>(
+        &self,
+        cause: ObligationCause<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        value: T,
+    ) -> InferOk<'tcx, T>
+    where
+        T: TypeFoldable<'tcx>,
+    {
+        debug!("partially_normalize_associated_types_in(value={:?})", value);
+        let mut selcx = traits::SelectionContext::new(self);
+        let traits::Normalized { value, obligations } =
+            traits::normalize(&mut selcx, param_env, cause, value);
+        debug!(
+            "partially_normalize_associated_types_in: result={:?} predicates={:?}",
+            value, obligations
+        );
+        InferOk { value, obligations }
+    }
+
+    fn type_implements_trait(
+        &self,
+        trait_def_id: DefId,
+        ty: Ty<'tcx>,
+        params: SubstsRef<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+    ) -> traits::EvaluationResult {
+        debug!(
+            "type_implements_trait: trait_def_id={:?}, type={:?}, params={:?}, param_env={:?}",
+            trait_def_id, ty, params, param_env
+        );
+
+        let trait_ref =
+            ty::TraitRef { def_id: trait_def_id, substs: self.tcx.mk_substs_trait(ty, params) };
+
+        let obligation = traits::Obligation {
+            cause: traits::ObligationCause::dummy(),
+            param_env,
+            recursion_depth: 0,
+            predicate: ty::Binder::dummy(trait_ref).without_const().to_predicate(self.tcx),
+        };
+        self.evaluate_obligation(&obligation).unwrap_or(traits::EvaluationResult::EvaluatedToErr)
+    }
+}
+
+pub trait InferCtxtBuilderExt<'tcx> {
+    fn enter_canonical_trait_query<K, R>(
+        &mut self,
+        canonical_key: &Canonical<'tcx, K>,
+        operation: impl FnOnce(&InferCtxt<'_, 'tcx>, &mut dyn TraitEngine<'tcx>, K) -> Fallible<R>,
+    ) -> Fallible<CanonicalizedQueryResponse<'tcx, R>>
+    where
+        K: TypeFoldable<'tcx>,
+        R: Debug + TypeFoldable<'tcx>,
+        Canonical<'tcx, QueryResponse<'tcx, R>>: ArenaAllocatable<'tcx>;
+}
+
+impl<'tcx> InferCtxtBuilderExt<'tcx> for InferCtxtBuilder<'tcx> {
+    /// The "main method" for a canonicalized trait query. Given the
+    /// canonical key `canonical_key`, this method will create a new
+    /// inference context, instantiate the key, and run your operation
+    /// `op`. The operation should yield up a result (of type `R`) as
+    /// well as a set of trait obligations that must be fully
+    /// satisfied. These obligations will be processed and the
+    /// canonical result created.
+    ///
+    /// Returns `NoSolution` in the event of any error.
+    ///
+    /// (It might be mildly nicer to implement this on `TyCtxt`, and
+    /// not `InferCtxtBuilder`, but that is a bit tricky right now.
+    /// In part because we would need a `for<'tcx>` sort of
+    /// bound for the closure and in part because it is convenient to
+    /// have `'tcx` be free on this function so that we can talk about
+    /// `K: TypeFoldable<'tcx>`.)
+    fn enter_canonical_trait_query<K, R>(
+        &mut self,
+        canonical_key: &Canonical<'tcx, K>,
+        operation: impl FnOnce(&InferCtxt<'_, 'tcx>, &mut dyn TraitEngine<'tcx>, K) -> Fallible<R>,
+    ) -> Fallible<CanonicalizedQueryResponse<'tcx, R>>
+    where
+        K: TypeFoldable<'tcx>,
+        R: Debug + TypeFoldable<'tcx>,
+        Canonical<'tcx, QueryResponse<'tcx, R>>: ArenaAllocatable<'tcx>,
+    {
+        self.enter_with_canonical(
+            DUMMY_SP,
+            canonical_key,
+            |ref infcx, key, canonical_inference_vars| {
+                let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
+                let value = operation(infcx, &mut *fulfill_cx, key)?;
+                infcx.make_canonicalized_query_response(
+                    canonical_inference_vars,
+                    value,
+                    &mut *fulfill_cx,
+                )
+            },
+        )
+    }
+}