Rollup merge of rust-lang#108350 - compiler-errors:assoc-type-bound-dogfooding, r=oli-obk

matthiaskrgr · web-flow · commit d6077f895aa8 · 2023-02-23T06:18:07.000+01:00
Use associated type bounds in some places in the compiler

Use associated type bounds for some nested `impl Trait&lt;Assoc = impl Trait2&gt;` cases. I'm generally keen to introduce new lang features that are more mature into the compiler, but maybe let's see what others think?

Side-note: I was surprised that the only use-cases of nested impl trait in the compiler are just iterator related?!
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
@@ -1,6 +1,7 @@
 //! This query borrow-checks the MIR to (further) ensure it is not broken.
 
 #![allow(rustc::potential_query_instability)]
+#![feature(associated_type_bounds)]
 #![feature(box_patterns)]
 #![feature(let_chains)]
 #![feature(min_specialization)]
diff --git a/compiler/rustc_borrowck/src/type_check/canonical.rs b/compiler/rustc_borrowck/src/type_check/canonical.rs
@@ -117,7 +117,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
     pub(super) fn prove_predicates(
         &mut self,
-        predicates: impl IntoIterator<Item = impl ToPredicate<'tcx> + std::fmt::Debug>,
+        predicates: impl IntoIterator<Item: ToPredicate<'tcx> + std::fmt::Debug>,
         locations: Locations,
         category: ConstraintCategory<'tcx>,
     ) {
diff --git a/compiler/rustc_infer/src/infer/combine.rs b/compiler/rustc_infer/src/infer/combine.rs
@@ -478,10 +478,7 @@ impl<'infcx, 'tcx> CombineFields<'infcx, 'tcx> {
         self.obligations.extend(obligations.into_iter());
     }
 
-    pub fn register_predicates(
-        &mut self,
-        obligations: impl IntoIterator<Item = impl ToPredicate<'tcx>>,
-    ) {
+    pub fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ToPredicate<'tcx>>) {
         self.obligations.extend(obligations.into_iter().map(|to_pred| {
             Obligation::new(self.infcx.tcx, self.trace.cause.clone(), self.param_env, to_pred)
         }))
@@ -814,10 +811,7 @@ pub trait ObligationEmittingRelation<'tcx>: TypeRelation<'tcx> {
     /// Register predicates that must hold in order for this relation to hold. Uses
     /// a default obligation cause, [`ObligationEmittingRelation::register_obligations`] should
     /// be used if control over the obligaton causes is required.
-    fn register_predicates(
-        &mut self,
-        obligations: impl IntoIterator<Item = impl ToPredicate<'tcx>>,
-    );
+    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ToPredicate<'tcx>>);
 
     /// Register an obligation that both constants must be equal to each other.
     ///
diff --git a/compiler/rustc_infer/src/infer/equate.rs b/compiler/rustc_infer/src/infer/equate.rs
@@ -201,10 +201,7 @@ impl<'tcx> TypeRelation<'tcx> for Equate<'_, '_, 'tcx> {
 }
 
 impl<'tcx> ObligationEmittingRelation<'tcx> for Equate<'_, '_, 'tcx> {
-    fn register_predicates(
-        &mut self,
-        obligations: impl IntoIterator<Item = impl ty::ToPredicate<'tcx>>,
-    ) {
+    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {
         self.fields.register_predicates(obligations);
     }
 
diff --git a/compiler/rustc_infer/src/infer/glb.rs b/compiler/rustc_infer/src/infer/glb.rs
@@ -148,10 +148,7 @@ impl<'combine, 'infcx, 'tcx> LatticeDir<'infcx, 'tcx> for Glb<'combine, 'infcx,
 }
 
 impl<'tcx> ObligationEmittingRelation<'tcx> for Glb<'_, '_, 'tcx> {
-    fn register_predicates(
-        &mut self,
-        obligations: impl IntoIterator<Item = impl ty::ToPredicate<'tcx>>,
-    ) {
+    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {
         self.fields.register_predicates(obligations);
     }
 
diff --git a/compiler/rustc_infer/src/infer/lub.rs b/compiler/rustc_infer/src/infer/lub.rs
@@ -148,10 +148,7 @@ impl<'combine, 'infcx, 'tcx> LatticeDir<'infcx, 'tcx> for Lub<'combine, 'infcx,
 }
 
 impl<'tcx> ObligationEmittingRelation<'tcx> for Lub<'_, '_, 'tcx> {
-    fn register_predicates(
-        &mut self,
-        obligations: impl IntoIterator<Item = impl ty::ToPredicate<'tcx>>,
-    ) {
+    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {
         self.fields.register_predicates(obligations);
     }
 
diff --git a/compiler/rustc_infer/src/infer/nll_relate/mod.rs b/compiler/rustc_infer/src/infer/nll_relate/mod.rs
@@ -763,10 +763,7 @@ impl<'tcx, D> ObligationEmittingRelation<'tcx> for TypeRelating<'_, 'tcx, D>
 where
     D: TypeRelatingDelegate<'tcx>,
 {
-    fn register_predicates(
-        &mut self,
-        obligations: impl IntoIterator<Item = impl ty::ToPredicate<'tcx>>,
-    ) {
+    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {
         self.delegate.register_obligations(
             obligations
                 .into_iter()
diff --git a/compiler/rustc_infer/src/infer/sub.rs b/compiler/rustc_infer/src/infer/sub.rs
@@ -228,10 +228,7 @@ impl<'tcx> TypeRelation<'tcx> for Sub<'_, '_, 'tcx> {
 }
 
 impl<'tcx> ObligationEmittingRelation<'tcx> for Sub<'_, '_, 'tcx> {
-    fn register_predicates(
-        &mut self,
-        obligations: impl IntoIterator<Item = impl ty::ToPredicate<'tcx>>,
-    ) {
+    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {
         self.fields.register_predicates(obligations);
     }
 
diff --git a/compiler/rustc_infer/src/lib.rs b/compiler/rustc_infer/src/lib.rs
@@ -13,6 +13,7 @@
 //! This API is completely unstable and subject to change.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
+#![feature(associated_type_bounds)]
 #![feature(box_patterns)]
 #![feature(control_flow_enum)]
 #![feature(extend_one)]
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
@@ -1856,7 +1856,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn mk_fn_def(
         self,
         def_id: DefId,
-        substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> Ty<'tcx> {
         let substs = self.check_substs(def_id, substs);
         self.mk_ty(FnDef(def_id, substs))
@@ -1866,7 +1866,7 @@ impl<'tcx> TyCtxt<'tcx> {
     fn check_substs(
         self,
         _def_id: DefId,
-        substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> SubstsRef<'tcx> {
         let substs = substs.into_iter().map(Into::into);
         #[cfg(debug_assertions)]
@@ -1901,7 +1901,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn mk_projection(
         self,
         item_def_id: DefId,
-        substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> Ty<'tcx> {
         self.mk_alias(ty::Projection, self.mk_alias_ty(item_def_id, substs))
     }
@@ -2293,7 +2293,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn mk_trait_ref(
         self,
         trait_def_id: DefId,
-        substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> ty::TraitRef<'tcx> {
         let substs = self.check_substs(trait_def_id, substs);
         ty::TraitRef { def_id: trait_def_id, substs, _use_mk_trait_ref_instead: () }
@@ -2302,7 +2302,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn mk_alias_ty(
         self,
         def_id: DefId,
-        substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> ty::AliasTy<'tcx> {
         let substs = self.check_substs(def_id, substs);
         ty::AliasTy { def_id, substs, _use_mk_alias_ty_instead: () }
@@ -2472,7 +2472,7 @@ impl<'tcx> TyCtxtAt<'tcx> {
     pub fn mk_trait_ref(
         self,
         trait_lang_item: LangItem,
-        substs: impl IntoIterator<Item = impl Into<ty::GenericArg<'tcx>>>,
+        substs: impl IntoIterator<Item: Into<ty::GenericArg<'tcx>>>,
     ) -> ty::TraitRef<'tcx> {
         let trait_def_id = self.require_lang_item(trait_lang_item, Some(self.span));
         self.tcx.mk_trait_ref(trait_def_id, substs)
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
@@ -568,7 +568,7 @@ impl<'tcx> GeneratorSubsts<'tcx> {
         self,
         def_id: DefId,
         tcx: TyCtxt<'tcx>,
-    ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
+    ) -> impl Iterator<Item: Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
         let layout = tcx.generator_layout(def_id).unwrap();
         layout.variant_fields.iter().map(move |variant| {
             variant.iter().map(move |field| {
diff --git a/compiler/rustc_mir_build/src/build/matches/test.rs b/compiler/rustc_mir_build/src/build/matches/test.rs
@@ -832,7 +832,7 @@ fn trait_method<'tcx>(
     tcx: TyCtxt<'tcx>,
     trait_def_id: DefId,
     method_name: Symbol,
-    substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+    substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
 ) -> ConstantKind<'tcx> {
     // The unhygienic comparison here is acceptable because this is only
     // used on known traits.
diff --git a/compiler/rustc_trait_selection/src/infer.rs b/compiler/rustc_trait_selection/src/infer.rs
@@ -42,7 +42,7 @@ pub trait InferCtxtExt<'tcx> {
     fn type_implements_trait(
         &self,
         trait_def_id: DefId,
-        params: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+        params: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
         param_env: ty::ParamEnv<'tcx>,
     ) -> traits::EvaluationResult;
 }
@@ -82,7 +82,7 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
     fn type_implements_trait(
         &self,
         trait_def_id: DefId,
-        params: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+        params: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
         param_env: ty::ParamEnv<'tcx>,
     ) -> traits::EvaluationResult {
         let trait_ref = self.tcx.mk_trait_ref(trait_def_id, params);
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/method_chain.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/method_chain.rs
@@ -98,7 +98,7 @@ impl<'tcx> ObligationEmittingRelation<'tcx> for CollectAllMismatches<'_, 'tcx> {
 
     fn register_predicates(
         &mut self,
-        _obligations: impl IntoIterator<Item = impl ty::ToPredicate<'tcx>>,
+        _obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>,
     ) {
         // FIXME(deferred_projection_equality)
     }
diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs
@@ -239,7 +239,7 @@ pub fn predicate_for_trait_def<'tcx>(
     cause: ObligationCause<'tcx>,
     trait_def_id: DefId,
     recursion_depth: usize,
-    params: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+    params: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
 ) -> PredicateObligation<'tcx> {
     let trait_ref = tcx.mk_trait_ref(trait_def_id, params);
     predicate_for_trait_ref(tcx, cause, param_env, trait_ref, recursion_depth)

Original file line number	Diff line number	Diff line change
`@@ -201,10 +201,7 @@ impl<'tcx> TypeRelation<'tcx> for Equate<'_, '_, 'tcx> {`
`201`	`201`	`}`
`202`	`202`
`203`	`203`	`impl<'tcx> ObligationEmittingRelation<'tcx> for Equate<'_, '_, 'tcx> {`
`204`		`- fn register_predicates(`
`205`		`- &mut self,`
`206`		`- obligations: impl IntoIterator<Item = impl ty::ToPredicate<'tcx>>,`
`207`		`- ) {`
	`204`	`+ fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {`
`208`	`205`	`self.fields.register_predicates(obligations);`
`209`	`206`	`}`
`210`	`207`
Original file line number	Diff line number	Diff line change
`@@ -148,10 +148,7 @@ impl<'combine, 'infcx, 'tcx> LatticeDir<'infcx, 'tcx> for Glb<'combine, 'infcx,`
`148`	`148`	`}`
`149`	`149`
`150`	`150`	`impl<'tcx> ObligationEmittingRelation<'tcx> for Glb<'_, '_, 'tcx> {`
`151`		`- fn register_predicates(`
`152`		`- &mut self,`
`153`		`- obligations: impl IntoIterator<Item = impl ty::ToPredicate<'tcx>>,`
`154`		`- ) {`
	`151`	`+ fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {`
`155`	`152`	`self.fields.register_predicates(obligations);`
`156`	`153`	`}`
`157`	`154`
Original file line number	Diff line number	Diff line change
`@@ -228,10 +228,7 @@ impl<'tcx> TypeRelation<'tcx> for Sub<'_, '_, 'tcx> {`
`228`	`228`	`}`
`229`	`229`
`230`	`230`	`impl<'tcx> ObligationEmittingRelation<'tcx> for Sub<'_, '_, 'tcx> {`
`231`		`- fn register_predicates(`
`232`		`- &mut self,`
`233`		`- obligations: impl IntoIterator<Item = impl ty::ToPredicate<'tcx>>,`
`234`		`- ) {`
	`231`	`+ fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {`
`235`	`232`	`self.fields.register_predicates(obligations);`
`236`	`233`	`}`
`237`	`234`