fast_reject: remove StripReferences

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -26,7 +26,7 @@ use rustc_middle::mir::interpret;
 use rustc_middle::thir;
 use rustc_middle::traits::specialization_graph;
 use rustc_middle::ty::codec::TyEncoder;
-use rustc_middle::ty::fast_reject::{self, SimplifiedType, SimplifyParams, StripReferences};
+use rustc_middle::ty::fast_reject::{self, SimplifiedType, SimplifyParams};
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{self, SymbolName, Ty, TyCtxt};
 use rustc_serialize::{opaque, Encodable, Encoder};
@@ -2066,7 +2066,6 @@ impl<'tcx, 'v> ItemLikeVisitor<'v> for ImplsVisitor<'tcx> {
                         self.tcx,
                         trait_ref.self_ty(),
                         SimplifyParams::No,
-                        StripReferences::No,
                     );
 
                     self.impls

compiler/rustc_middle/src/ty/fast_reject.rs

@@ -54,12 +54,6 @@ pub enum SimplifyParams {
     No,
 }
 
-#[derive(PartialEq, Eq, Debug, Clone, Copy)]
-pub enum StripReferences {
-    Yes,
-    No,
-}
-
 /// Tries to simplify a type by only returning the outermost injective¹ layer, if one exists.
 ///
 /// The idea is to get something simple that we can use to quickly decide if two types could unify,
@@ -73,8 +67,6 @@ pub enum StripReferences {
 /// When using `SimplifyParams::Yes`, we still return a simplified type for params and projections²,
 /// the reasoning for this can be seen at the places doing this.
 ///
-/// For diagnostics we strip references with `StripReferences::Yes`. This is currently the best
-/// way to skip some unhelpful suggestions.
 ///
 /// ¹ meaning that if two outermost layers are different, then the whole types are also different.
 /// ² FIXME(@lcnr): this seems like it can actually end up being unsound with the way it's used during
@@ -87,7 +79,6 @@ pub fn simplify_type(
     tcx: TyCtxt<'_>,
     ty: Ty<'_>,
     can_simplify_params: SimplifyParams,
-    strip_references: StripReferences,
 ) -> Option<SimplifiedType> {
     match *ty.kind() {
         ty::Bool => Some(BoolSimplifiedType),
@@ -106,16 +97,7 @@ pub fn simplify_type(
             }
             _ => Some(MarkerTraitObjectSimplifiedType),
         },
-        ty::Ref(_, ty, mutbl) => {
+        ty::Ref(_, _, mutbl) => Some(RefSimplifiedType(mutbl)),
-            if strip_references == StripReferences::Yes {
-                // For diagnostics, when recommending similar impls we want to
-                // recommend impls even when there is a reference mismatch,
-                // so we treat &T and T equivalently in that case.
-                simplify_type(tcx, ty, can_simplify_params, strip_references)
-            } else {
-                Some(RefSimplifiedType(mutbl))
-            }
-        }
         ty::FnDef(def_id, _) | ty::Closure(def_id, _) => Some(ClosureSimplifiedType(def_id)),
         ty::Generator(def_id, _, _) => Some(GeneratorSimplifiedType(def_id)),
         ty::GeneratorWitness(ref tys) => {

compiler/rustc_middle/src/ty/trait_def.rs

@@ -1,5 +1,5 @@
 use crate::traits::specialization_graph;
-use crate::ty::fast_reject::{self, SimplifiedType, SimplifyParams, StripReferences};
+use crate::ty::fast_reject::{self, SimplifiedType, SimplifyParams};
 use crate::ty::fold::TypeFoldable;
 use crate::ty::{Ident, Ty, TyCtxt};
 use rustc_hir as hir;
@@ -150,9 +150,7 @@ impl<'tcx> TyCtxt<'tcx> {
         self_ty: Ty<'tcx>,
     ) -> impl Iterator<Item = DefId> + 'tcx {
         let impls = self.trait_impls_of(def_id);
-        if let Some(simp) =
+        if let Some(simp) = fast_reject::simplify_type(self, self_ty, SimplifyParams::No) {
-            fast_reject::simplify_type(self, self_ty, SimplifyParams::No, StripReferences::No)
-        {
             if let Some(impls) = impls.non_blanket_impls.get(&simp) {
                 return impls.iter().copied();
             }
@@ -189,9 +187,7 @@ impl<'tcx> TyCtxt<'tcx> {
         // whose outer level is not a parameter or projection. Especially for things like
         // `T: Clone` this is incredibly useful as we would otherwise look at all the impls
         // of `Clone` for `Option<T>`, `Vec<T>`, `ConcreteType` and so on.
-        if let Some(simp) =
+        if let Some(simp) = fast_reject::simplify_type(self, self_ty, SimplifyParams::Yes) {
-            fast_reject::simplify_type(self, self_ty, SimplifyParams::Yes, StripReferences::No)
-        {
             if let Some(impls) = impls.non_blanket_impls.get(&simp) {
                 for &impl_def_id in impls {
                     if let result @ Some(_) = f(impl_def_id) {
@@ -251,7 +247,7 @@ pub(super) fn trait_impls_of_provider(tcx: TyCtxt<'_>, trait_id: DefId) -> Trait
         }
 
         if let Some(simplified_self_ty) =
-            fast_reject::simplify_type(tcx, impl_self_ty, SimplifyParams::No, StripReferences::No)
+            fast_reject::simplify_type(tcx, impl_self_ty, SimplifyParams::No)
         {
             impls.non_blanket_impls.entry(simplified_self_ty).or_default().push(impl_def_id);
         } else {

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -15,7 +15,7 @@ use crate::traits::{
 };
 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 use rustc_middle::traits::specialization_graph::OverlapMode;
-use rustc_middle::ty::fast_reject::{self, SimplifyParams, StripReferences};
+use rustc_middle::ty::fast_reject::{self, SimplifyParams};
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::subst::Subst;
 use rustc_middle::ty::{self, Ty, TyCtxt};
@@ -82,8 +82,8 @@ where
         impl2_ref.iter().flat_map(|tref| tref.substs.types()),
     )
     .any(|(ty1, ty2)| {
-        let t1 = fast_reject::simplify_type(tcx, ty1, SimplifyParams::No, StripReferences::No);
+        let t1 = fast_reject::simplify_type(tcx, ty1, SimplifyParams::No);
-        let t2 = fast_reject::simplify_type(tcx, ty2, SimplifyParams::No, StripReferences::No);
+        let t2 = fast_reject::simplify_type(tcx, ty2, SimplifyParams::No);
 
         if let (Some(t1), Some(t2)) = (t1, t2) {
             // Simplified successfully

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -36,7 +36,7 @@ use rustc_infer::infer::LateBoundRegionConversionTime;
 use rustc_middle::dep_graph::{DepKind, DepNodeIndex};
 use rustc_middle::mir::interpret::ErrorHandled;
 use rustc_middle::thir::abstract_const::NotConstEvaluatable;
-use rustc_middle::ty::fast_reject::{self, SimplifyParams, StripReferences};
+use rustc_middle::ty::fast_reject::{self, SimplifyParams};
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::relate::TypeRelation;
 use rustc_middle::ty::subst::{GenericArgKind, Subst, SubstsRef};
@@ -2172,14 +2172,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                             self.tcx(),
                             obligation_ty,
                             SimplifyParams::Yes,
-                            StripReferences::No,
-                        );
-                        let simplified_impl_ty = fast_reject::simplify_type(
-                            self.tcx(),
-                            impl_ty,
-                            SimplifyParams::No,
-                            StripReferences::No,
                         );
+                        let simplified_impl_ty =
+                            fast_reject::simplify_type(self.tcx(), impl_ty, SimplifyParams::No);
 
                         simplified_obligation_ty.is_some()
                             && simplified_impl_ty.is_some()

compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs

@@ -2,7 +2,7 @@ use super::OverlapError;
 
 use crate::traits;
 use rustc_hir::def_id::DefId;
-use rustc_middle::ty::fast_reject::{self, SimplifiedType, SimplifyParams, StripReferences};
+use rustc_middle::ty::fast_reject::{self, SimplifiedType, SimplifyParams};
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{self, TyCtxt, TypeFoldable};
 
@@ -49,12 +49,7 @@ impl ChildrenExt<'_> for Children {
     /// Insert an impl into this set of children without comparing to any existing impls.
     fn insert_blindly(&mut self, tcx: TyCtxt<'_>, impl_def_id: DefId) {
         let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
-        if let Some(st) = fast_reject::simplify_type(
+        if let Some(st) = fast_reject::simplify_type(tcx, trait_ref.self_ty(), SimplifyParams::No) {
-            tcx,
-            trait_ref.self_ty(),
-            SimplifyParams::No,
-            StripReferences::No,
-        ) {
             debug!("insert_blindly: impl_def_id={:?} st={:?}", impl_def_id, st);
             self.non_blanket_impls.entry(st).or_default().push(impl_def_id)
         } else {
@@ -69,12 +64,7 @@ impl ChildrenExt<'_> for Children {
     fn remove_existing(&mut self, tcx: TyCtxt<'_>, impl_def_id: DefId) {
         let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
         let vec: &mut Vec<DefId>;
-        if let Some(st) = fast_reject::simplify_type(
+        if let Some(st) = fast_reject::simplify_type(tcx, trait_ref.self_ty(), SimplifyParams::No) {
-            tcx,
-            trait_ref.self_ty(),
-            SimplifyParams::No,
-            StripReferences::No,
-        ) {
             debug!("remove_existing: impl_def_id={:?} st={:?}", impl_def_id, st);
             vec = self.non_blanket_impls.get_mut(&st).unwrap();
         } else {
@@ -322,12 +312,7 @@ impl GraphExt for Graph {
 
         let mut parent = trait_def_id;
         let mut last_lint = None;
-        let simplified = fast_reject::simplify_type(
+        let simplified = fast_reject::simplify_type(tcx, trait_ref.self_ty(), SimplifyParams::No);
-            tcx,
-            trait_ref.self_ty(),
-            SimplifyParams::No,
-            StripReferences::No,
-        );
 
         // Descend the specialization tree, where `parent` is the current parent node.
         loop {

compiler/rustc_typeck/src/check/method/suggest.rs

@@ -9,7 +9,7 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{ExprKind, Node, QPath};
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
-use rustc_middle::ty::fast_reject::{simplify_type, SimplifyParams, StripReferences};
+use rustc_middle::ty::fast_reject::{simplify_type, SimplifyParams};
 use rustc_middle::ty::print::with_crate_prefix;
 use rustc_middle::ty::{self, DefIdTree, ToPredicate, Ty, TyCtxt, TypeFoldable};
 use rustc_span::lev_distance;
@@ -1748,8 +1748,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // FIXME: Even though negative bounds are not implemented, we could maybe handle
                 // cases where a positive bound implies a negative impl.
                 (candidates, Vec::new())
-            } else if let Some(simp_rcvr_ty) =
+            } else if let Some(simp_rcvr_ty) = simplify_type(self.tcx, rcvr_ty, SimplifyParams::Yes)
-                simplify_type(self.tcx, rcvr_ty, SimplifyParams::Yes, StripReferences::No)
             {
                 let mut potential_candidates = Vec::new();
                 let mut explicitly_negative = Vec::new();
@@ -1763,12 +1762,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         })
                         .any(|imp_did| {
                             let imp = self.tcx.impl_trait_ref(imp_did).unwrap();
-                            let imp_simp = simplify_type(
+                            let imp_simp =
-                                self.tcx,
+                                simplify_type(self.tcx, imp.self_ty(), SimplifyParams::Yes);
-                                imp.self_ty(),
-                                SimplifyParams::Yes,
-                                StripReferences::No,
-                            );
                             imp_simp.map_or(false, |s| s == simp_rcvr_ty)
                         })
                     {