Stop passing traitref/traitpredicate by ref

compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs

@@ -537,7 +537,7 @@ impl<T> Trait<T> for X {
         for pred in hir_generics.bounds_for_param(def_id) {
             if self.constrain_generic_bound_associated_type_structured_suggestion(
                 diag,
-                &trait_ref,
+                trait_ref,
                 pred.bounds,
                 assoc,
                 assoc_args,
@@ -706,7 +706,7 @@ fn foo(&self) -> Self::T { String::new() }
 
             self.constrain_generic_bound_associated_type_structured_suggestion(
                 diag,
-                &trait_ref,
+                trait_ref,
                 opaque_hir_ty.bounds,
                 assoc,
                 assoc_args,
@@ -860,7 +860,7 @@ fn foo(&self) -> Self::T { String::new() }
     fn constrain_generic_bound_associated_type_structured_suggestion(
         &self,
         diag: &mut Diag<'_>,
-        trait_ref: &ty::TraitRef<'tcx>,
+        trait_ref: ty::TraitRef<'tcx>,
         bounds: hir::GenericBounds<'_>,
         assoc: ty::AssocItem,
         assoc_args: &[ty::GenericArg<'tcx>],

compiler/rustc_infer/src/traits/util.rs

@@ -285,8 +285,7 @@ impl<'tcx, O: Elaboratable<'tcx>> Elaborator<'tcx, O> {
                 let obligations =
                     predicates.predicates.iter().enumerate().map(|(index, &(clause, span))| {
                         elaboratable.child_with_derived_cause(
-                            clause
-                                .instantiate_supertrait(tcx, &bound_clause.rebind(data.trait_ref)),
+                            clause.instantiate_supertrait(tcx, bound_clause.rebind(data.trait_ref)),
                             span,
                             bound_clause.rebind(data),
                             index,

compiler/rustc_middle/src/traits/util.rs

@@ -37,7 +37,7 @@ impl<'tcx> Elaborator<'tcx> {
         let super_predicates =
             self.tcx.super_predicates_of(trait_ref.def_id()).predicates.iter().filter_map(
                 |&(pred, _)| {
-                    let clause = pred.instantiate_supertrait(self.tcx, &trait_ref);
+                    let clause = pred.instantiate_supertrait(self.tcx, trait_ref);
                     self.visited.insert(clause).then_some(clause)
                 },
             );

compiler/rustc_middle/src/ty/predicate.rs

@@ -313,7 +313,7 @@ impl<'tcx> Clause<'tcx> {
     pub fn instantiate_supertrait(
         self,
         tcx: TyCtxt<'tcx>,
-        trait_ref: &ty::PolyTraitRef<'tcx>,
+        trait_ref: ty::PolyTraitRef<'tcx>,
     ) -> Clause<'tcx> {
         // The interaction between HRTB and supertraits is not entirely
         // obvious. Let me walk you (and myself) through an example.

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -3597,7 +3597,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         &self,
         obligation: &PredicateObligation<'tcx>,
         err: &mut Diag<'_>,
-        trait_ref: &ty::PolyTraitRef<'tcx>,
+        trait_ref: ty::PolyTraitRef<'tcx>,
     ) {
         let rhs_span = match obligation.cause.code() {
             ObligationCauseCode::BinOp { rhs_span: Some(span), rhs_is_lit, .. } if *rhs_is_lit => {
@@ -4822,7 +4822,7 @@ impl<'a, 'hir> hir::intravisit::Visitor<'hir> for ReplaceImplTraitVisitor<'a> {
 pub(super) fn get_explanation_based_on_obligation<'tcx>(
     tcx: TyCtxt<'tcx>,
     obligation: &PredicateObligation<'tcx>,
-    trait_predicate: &ty::PolyTraitPredicate<'tcx>,
+    trait_predicate: ty::PolyTraitPredicate<'tcx>,
     pre_message: String,
 ) -> String {
     if let ObligationCauseCode::MainFunctionType = obligation.cause.code() {

compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs

@@ -530,7 +530,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                         };
 
                         let err_msg = self.get_standard_error_message(
-                            &main_trait_predicate,
+                            main_trait_predicate,
                             message,
                             predicate_is_const,
                             append_const_msg,
@@ -601,7 +601,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                         let explanation = get_explanation_based_on_obligation(
                             self.tcx,
                             &obligation,
-                            &main_trait_predicate,
+                            trait_predicate,
                             pre_message,
                         );
 
@@ -652,7 +652,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
 
                         let UnsatisfiedConst(unsatisfied_const) = self
                             .maybe_add_note_for_unsatisfied_const(
-                                &trait_predicate,
+                                trait_predicate,
                                 &mut err,
                                 span,
                             );
@@ -669,7 +669,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                             err.span_label(tcx.def_span(body), s);
                         }
 
-                        self.suggest_floating_point_literal(&obligation, &mut err, &main_trait_ref);
+                        self.suggest_floating_point_literal(&obligation, &mut err, main_trait_ref);
                         self.suggest_dereferencing_index(&obligation, &mut err, trait_predicate);
                         suggested |= self.suggest_dereferences(&obligation, &mut err, trait_predicate);
                         suggested |= self.suggest_fn_call(&obligation, &mut err, trait_predicate);
@@ -704,7 +704,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                             span,
                             trait_predicate,
                         );
-                        self.note_version_mismatch(&mut err, &main_trait_ref);
+                        self.note_version_mismatch(&mut err, main_trait_ref);
                         self.suggest_remove_await(&obligation, &mut err);
                         self.suggest_derive(&obligation, &mut err, trait_predicate);
 
@@ -752,7 +752,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
 
                         self.try_to_add_help_message(
                             &obligation,
-                            &main_trait_predicate,
+                            main_trait_predicate,
                             &mut err,
                             span,
                             is_fn_trait,
@@ -2224,11 +2224,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
     /// If the `Self` type of the unsatisfied trait `trait_ref` implements a trait
     /// with the same path as `trait_ref`, a help message about
     /// a probable version mismatch is added to `err`
-    fn note_version_mismatch(
-        &self,
-        err: &mut Diag<'_>,
-        trait_ref: &ty::PolyTraitRef<'tcx>,
-    ) -> bool {
+    fn note_version_mismatch(&self, err: &mut Diag<'_>, trait_ref: ty::PolyTraitRef<'tcx>) -> bool {
         let get_trait_impls = |trait_def_id| {
             let mut trait_impls = vec![];
             self.tcx.for_each_relevant_impl(
@@ -3032,7 +3028,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
 
     fn get_standard_error_message(
         &self,
-        trait_predicate: &ty::PolyTraitPredicate<'tcx>,
+        trait_predicate: ty::PolyTraitPredicate<'tcx>,
         message: Option<String>,
         predicate_is_const: bool,
         append_const_msg: Option<AppendConstMessage>,
@@ -3203,7 +3199,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
     fn try_to_add_help_message(
         &self,
         obligation: &PredicateObligation<'tcx>,
-        trait_predicate: &ty::PolyTraitPredicate<'tcx>,
+        trait_predicate: ty::PolyTraitPredicate<'tcx>,
         err: &mut Diag<'_>,
         span: Span,
         is_fn_trait: bool,
@@ -3235,7 +3231,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 params,
             );
         } else if !trait_predicate.has_non_region_infer()
-            && self.predicate_can_apply(obligation.param_env, *trait_predicate)
+            && self.predicate_can_apply(obligation.param_env, trait_predicate)
         {
             // If a where-clause may be useful, remind the
             // user that they can add it.
@@ -3246,7 +3242,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             // which is somewhat confusing.
             self.suggest_restricting_param_bound(
                 err,
-                *trait_predicate,
+                trait_predicate,
                 None,
                 obligation.cause.body_id,
             );
@@ -3261,7 +3257,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             );
         } else if !suggested && !unsatisfied_const {
             // Can't show anything else useful, try to find similar impls.
-            let impl_candidates = self.find_similar_impl_candidates(*trait_predicate);
+            let impl_candidates = self.find_similar_impl_candidates(trait_predicate);
             if !self.report_similar_impl_candidates(
                 &impl_candidates,
                 trait_predicate.to_poly_trait_ref(),
@@ -3272,7 +3268,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             ) {
                 self.report_similar_impl_candidates_for_root_obligation(
                     obligation,
-                    *trait_predicate,
+                    trait_predicate,
                     body_def_id,
                     err,
                 );
@@ -3346,7 +3342,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
 
     fn maybe_add_note_for_unsatisfied_const(
         &self,
-        _trait_predicate: &ty::PolyTraitPredicate<'tcx>,
+        _trait_predicate: ty::PolyTraitPredicate<'tcx>,
         _err: &mut Diag<'_>,
         _span: Span,
     ) -> UnsatisfiedConst {

compiler/rustc_trait_selection/src/traits/object_safety.rs

@@ -194,7 +194,7 @@ fn predicates_reference_self(
     predicates
         .predicates
         .iter()
-        .map(|&(predicate, sp)| (predicate.instantiate_supertrait(tcx, &trait_ref), sp))
+        .map(|&(predicate, sp)| (predicate.instantiate_supertrait(tcx, trait_ref), sp))
         .filter_map(|predicate| predicate_references_self(tcx, predicate))
         .collect()
 }

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

@@ -1866,7 +1866,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         // the param_env so that it can be given the lowest priority. See
         // #50825 for the motivation for this.
         let is_global =
-            |cand: &ty::PolyTraitPredicate<'tcx>| cand.is_global() && !cand.has_bound_vars();
+            |cand: ty::PolyTraitPredicate<'tcx>| cand.is_global() && !cand.has_bound_vars();
 
         // (*) Prefer `BuiltinCandidate { has_nested: false }`, `PointeeCandidate`,
         // `DiscriminantKindCandidate`, `ConstDestructCandidate`
@@ -1909,7 +1909,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
             }
 
             (
-                ParamCandidate(ref other_cand),
+                ParamCandidate(other_cand),
                 ImplCandidate(..)
                 | AutoImplCandidate
                 | ClosureCandidate { .. }
@@ -1934,12 +1934,12 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 //
                 // Global bounds from the where clause should be ignored
                 // here (see issue #50825).
-                DropVictim::drop_if(!is_global(other_cand))
+                DropVictim::drop_if(!is_global(*other_cand))
             }
-            (ObjectCandidate(_) | ProjectionCandidate(_), ParamCandidate(ref victim_cand)) => {
+            (ObjectCandidate(_) | ProjectionCandidate(_), ParamCandidate(victim_cand)) => {
                 // Prefer these to a global where-clause bound
                 // (see issue #50825).
-                if is_global(victim_cand) { DropVictim::Yes } else { DropVictim::No }
+                if is_global(*victim_cand) { DropVictim::Yes } else { DropVictim::No }
             }
             (
                 ImplCandidate(_)
@@ -1957,12 +1957,12 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 | TraitUpcastingUnsizeCandidate(_)
                 | BuiltinCandidate { has_nested: true }
                 | TraitAliasCandidate,
-                ParamCandidate(ref victim_cand),
+                ParamCandidate(victim_cand),
             ) => {
                 // Prefer these to a global where-clause bound
                 // (see issue #50825).
                 DropVictim::drop_if(
-                    is_global(victim_cand) && other.evaluation.must_apply_modulo_regions(),
+                    is_global(*victim_cand) && other.evaluation.must_apply_modulo_regions(),
                 )
             }
 

compiler/rustc_trait_selection/src/traits/util.rs

@@ -132,7 +132,7 @@ impl<'tcx> TraitAliasExpander<'tcx> {
         debug!(?predicates);
 
         let items = predicates.predicates.iter().rev().filter_map(|(pred, span)| {
-            pred.instantiate_supertrait(tcx, &trait_ref)
+            pred.instantiate_supertrait(tcx, trait_ref)
                 .as_trait_clause()
                 .map(|trait_ref| item.clone_and_push(trait_ref.map_bound(|t| t.trait_ref), *span))
         });

compiler/rustc_trait_selection/src/traits/vtable.rs

@@ -125,7 +125,7 @@ fn prepare_vtable_segments_inner<'tcx, T>(
                 .predicates
                 .into_iter()
                 .filter_map(move |(pred, _)| {
-                    pred.instantiate_supertrait(tcx, &inner_most_trait_ref).as_trait_clause()
+                    pred.instantiate_supertrait(tcx, inner_most_trait_ref).as_trait_clause()
                 });
 
             // Find an unvisited supertrait

tests/ui/auto-traits/typeck-default-trait-impl-precedence.stderr

@@ -2,7 +2,7 @@ error[E0277]: the trait bound `&'static u32: Defaulted` is not satisfied
   --> $DIR/typeck-default-trait-impl-precedence.rs:19:20
    |
 LL |     is_defaulted::<&'static u32>();
-   |                    ^^^^^^^^^^^^ the trait `Defaulted` is not implemented for `&'static u32`, which is required by `&'static u32: Defaulted`
+   |                    ^^^^^^^^^^^^ the trait `Signed` is not implemented for `u32`, which is required by `&'static u32: Defaulted`
    |
 note: required for `&'static u32` to implement `Defaulted`
   --> $DIR/typeck-default-trait-impl-precedence.rs:10:19

tests/ui/generic-associated-types/assume-gat-normalization-for-nested-goals.next.stderr

@@ -2,7 +2,7 @@ error[E0277]: the trait bound `i32: Baz<Self>` is not satisfied
   --> $DIR/assume-gat-normalization-for-nested-goals.rs:9:30
    |
 LL |     type Bar<T>: Baz<Self> = i32;
-   |                              ^^^ the trait `Eq<i32>` is not implemented for `i32`, which is required by `i32: Baz<Self>`
+   |                              ^^^ the trait `Eq<i32>` is not implemented for `<Self as Foo>::Bar<()>`, which is required by `i32: Baz<Self>`
    |
 note: required for `i32` to implement `Baz<Self>`
   --> $DIR/assume-gat-normalization-for-nested-goals.rs:16:23
@@ -14,10 +14,10 @@ note: required by a bound in `Foo::Bar`
    |
 LL |     type Bar<T>: Baz<Self> = i32;
    |                  ^^^^^^^^^ required by this bound in `Foo::Bar`
-help: consider further restricting the associated type
+help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
    |
-LL | trait Foo where <Self as Foo>::Bar<()>: Eq<i32> {
-   |           +++++++++++++++++++++++++++++++++++++
+LL | trait Foo where i32: Baz<Self> {
+   |           ++++++++++++++++++++
 
 error: aborting due to 1 previous error
 

tests/ui/impl-trait/nested_impl_trait.stderr

@@ -42,29 +42,67 @@ LL | fn bad_in_fn_syntax(x: fn() -> impl Into<impl Debug>) {}
    |
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
+error[E0391]: cycle detected when computing type of `bad_in_ret_position::{opaque#0}`
+  --> $DIR/nested_impl_trait.rs:6:46
+   |
+LL | fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
+   |                                              ^^^^^^^^^^^^^^^^^^^^^
+   |
+note: ...which requires computing type of opaque `bad_in_ret_position::{opaque#0}`...
+  --> $DIR/nested_impl_trait.rs:6:46
+   |
+LL | fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
+   |                                              ^^^^^^^^^^^^^^^^^^^^^
+note: ...which requires type-checking `bad_in_ret_position`...
+  --> $DIR/nested_impl_trait.rs:6:1
+   |
+LL | fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: ...which again requires computing type of `bad_in_ret_position::{opaque#0}`, completing the cycle
+note: cycle used when checking that `bad_in_ret_position::{opaque#0}` is well-formed
+  --> $DIR/nested_impl_trait.rs:6:46
+   |
+LL | fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
+   |                                              ^^^^^^^^^^^^^^^^^^^^^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
+
 error[E0277]: the trait bound `impl Into<u32>: Into<impl Debug>` is not satisfied
   --> $DIR/nested_impl_trait.rs:6:46
    |
 LL | fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
    |                                              ^^^^^^^^^^^^^^^^^^^^^ the trait `Debug` is not implemented for `impl Into<u32>`
+
+error[E0391]: cycle detected when computing type of `<impl at $DIR/nested_impl_trait.rs:18:1: 18:7>::bad::{opaque#0}`
+  --> $DIR/nested_impl_trait.rs:19:34
+   |
+LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
+   |                                  ^^^^^^^^^^^^^^^^^^^^^
    |
-help: consider further restricting this bound
+note: ...which requires computing type of opaque `<impl at $DIR/nested_impl_trait.rs:18:1: 18:7>::bad::{opaque#0}`...
+  --> $DIR/nested_impl_trait.rs:19:34
+   |
+LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
+   |                                  ^^^^^^^^^^^^^^^^^^^^^
+note: ...which requires type-checking `<impl at $DIR/nested_impl_trait.rs:18:1: 18:7>::bad`...
+  --> $DIR/nested_impl_trait.rs:19:5
    |
-LL | fn bad_in_ret_position(x: impl Into<u32> + std::fmt::Debug) -> impl Into<impl Debug> { x }
-   |                                          +++++++++++++++++
+LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: ...which again requires computing type of `<impl at $DIR/nested_impl_trait.rs:18:1: 18:7>::bad::{opaque#0}`, completing the cycle
+note: cycle used when checking that `<impl at $DIR/nested_impl_trait.rs:18:1: 18:7>::bad::{opaque#0}` is well-formed
+  --> $DIR/nested_impl_trait.rs:19:34
+   |
+LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
+   |                                  ^^^^^^^^^^^^^^^^^^^^^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
 
 error[E0277]: the trait bound `impl Into<u32>: Into<impl Debug>` is not satisfied
   --> $DIR/nested_impl_trait.rs:19:34
    |
 LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
    |                                  ^^^^^^^^^^^^^^^^^^^^^ the trait `Debug` is not implemented for `impl Into<u32>`
-   |
-help: consider further restricting this bound
-   |
-LL |     fn bad(x: impl Into<u32> + std::fmt::Debug) -> impl Into<impl Debug> { x }
-   |                              +++++++++++++++++
 
-error: aborting due to 7 previous errors
+error: aborting due to 9 previous errors
 
-Some errors have detailed explanations: E0277, E0562, E0666.
+Some errors have detailed explanations: E0277, E0391, E0562, E0666.
 For more information about an error, try `rustc --explain E0277`.

tests/ui/kindck/kindck-send-object.stderr

@@ -4,7 +4,7 @@ error[E0277]: `&'static (dyn Dummy + 'static)` cannot be sent between threads sa
 LL |     assert_send::<&'static (dyn Dummy + 'static)>();
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `&'static (dyn Dummy + 'static)` cannot be sent between threads safely
    |
-   = help: the trait `Sync` is not implemented for `&'static (dyn Dummy + 'static)`, which is required by `&'static (dyn Dummy + 'static): Send`
+   = help: the trait `Sync` is not implemented for `(dyn Dummy + 'static)`, which is required by `&'static (dyn Dummy + 'static): Send`
    = note: required for `&'static (dyn Dummy + 'static)` to implement `Send`
 note: required by a bound in `assert_send`
   --> $DIR/kindck-send-object.rs:5:18