TypeVisitor: use std::ops::ControlFlow instead of bool

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

@@ -71,6 +71,7 @@ use rustc_middle::ty::{
 };
 use rustc_span::{BytePos, DesugaringKind, Pos, Span};
 use rustc_target::spec::abi;
+use std::ops::ControlFlow;
 use std::{cmp, fmt};
 
 mod note;
@@ -1497,7 +1498,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         }
 
         impl<'tcx> ty::fold::TypeVisitor<'tcx> for OpaqueTypesVisitor<'tcx> {
-            fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
+            fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<()> {
                 if let Some((kind, def_id)) = TyCategory::from_ty(t) {
                     let span = self.tcx.def_span(def_id);
                     // Avoid cluttering the output when the "found" and error span overlap:

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs

@@ -15,6 +15,8 @@ use rustc_middle::ty::{self, AssocItemContainer, RegionKind, Ty, TypeFoldable, T
 use rustc_span::symbol::Ident;
 use rustc_span::{MultiSpan, Span};
 
+use std::ops::ControlFlow;
+
 impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
     /// Print the error message for lifetime errors when the return type is a static `impl Trait`,
     /// `dyn Trait` or if a method call on a trait object introduces a static requirement.
@@ -472,13 +474,13 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
 struct TraitObjectVisitor(Vec<DefId>);
 
 impl TypeVisitor<'_> for TraitObjectVisitor {
-    fn visit_ty(&mut self, t: Ty<'_>) -> bool {
+    fn visit_ty(&mut self, t: Ty<'_>) -> ControlFlow<()> {
         match t.kind() {
             ty::Dynamic(preds, RegionKind::ReStatic) => {
                 if let Some(def_id) = preds.principal_def_id() {
                     self.0.push(def_id);
                 }
-                false
+                ControlFlow::CONTINUE
             }
             _ => t.super_visit_with(self),
         }

compiler/rustc_infer/src/infer/nll_relate/mod.rs

@@ -30,6 +30,7 @@ use rustc_middle::ty::fold::{TypeFoldable, TypeVisitor};
 use rustc_middle::ty::relate::{self, Relate, RelateResult, TypeRelation};
 use rustc_middle::ty::{self, InferConst, Ty, TyCtxt};
 use std::fmt::Debug;
+use std::ops::ControlFlow;
 
 #[derive(PartialEq)]
 pub enum NormalizationStrategy {
@@ -740,15 +741,15 @@ struct ScopeInstantiator<'me, 'tcx> {
 }
 
 impl<'me, 'tcx> TypeVisitor<'tcx> for ScopeInstantiator<'me, 'tcx> {
-    fn visit_binder<T: TypeFoldable<'tcx>>(&mut self, t: &ty::Binder<T>) -> bool {
+    fn visit_binder<T: TypeFoldable<'tcx>>(&mut self, t: &ty::Binder<T>) -> ControlFlow<()> {
         self.target_index.shift_in(1);
         t.super_visit_with(self);
         self.target_index.shift_out(1);
 
-        false
+        ControlFlow::CONTINUE
     }
 
-    fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
+    fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<()> {
         let ScopeInstantiator { bound_region_scope, next_region, .. } = self;
 
         match r {
@@ -759,7 +760,7 @@ impl<'me, 'tcx> TypeVisitor<'tcx> for ScopeInstantiator<'me, 'tcx> {
             _ => {}
         }
 
-        false
+        ControlFlow::CONTINUE
     }
 }
 

compiler/rustc_infer/src/infer/resolve.rs

@@ -3,6 +3,8 @@ use super::{FixupError, FixupResult, InferCtxt, Span};
 use rustc_middle::ty::fold::{TypeFolder, TypeVisitor};
 use rustc_middle::ty::{self, Const, InferConst, Ty, TyCtxt, TypeFoldable};
 
+use std::ops::ControlFlow;
+
 ///////////////////////////////////////////////////////////////////////////
 // OPPORTUNISTIC VAR RESOLVER
 
@@ -121,7 +123,7 @@ impl<'a, 'tcx> UnresolvedTypeFinder<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> TypeVisitor<'tcx> for UnresolvedTypeFinder<'a, 'tcx> {
-    fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
+    fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<()> {
         let t = self.infcx.shallow_resolve(t);
         if t.has_infer_types() {
             if let ty::Infer(infer_ty) = *t.kind() {
@@ -143,15 +145,15 @@ impl<'a, 'tcx> TypeVisitor<'tcx> for UnresolvedTypeFinder<'a, 'tcx> {
                     None
                 };
                 self.first_unresolved = Some((t, ty_var_span));
-                true // Halt visiting.
+                ControlFlow::BREAK
             } else {
                 // Otherwise, visit its contents.
                 t.super_visit_with(self)
             }
         } else {
             // All type variables in inference types must already be resolved,
             // - no need to visit the contents, continue visiting.
-            false
+            ControlFlow::CONTINUE
         }
     }
 }

compiler/rustc_infer/src/lib.rs

@@ -22,6 +22,7 @@
 #![feature(never_type)]
 #![feature(or_patterns)]
 #![feature(in_band_lifetimes)]
+#![feature(control_flow_enum)]
 #![recursion_limit = "512"] // For rustdoc
 
 #[macro_use]

compiler/rustc_infer/src/traits/structural_impls.rs

@@ -4,6 +4,7 @@ use rustc_middle::ty;
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
 
 use std::fmt;
+use std::ops::ControlFlow;
 
 // Structural impls for the structs in `traits`.
 
@@ -68,7 +69,7 @@ impl<'tcx, O: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::Obligation<'tcx
         }
     }
 
-    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<()> {
         self.predicate.visit_with(visitor)
     }
 }

compiler/rustc_lint/src/lib.rs

@@ -37,6 +37,7 @@
 #![feature(or_patterns)]
 #![feature(half_open_range_patterns)]
 #![feature(exclusive_range_pattern)]
+#![feature(control_flow_enum)]
 #![recursion_limit = "256"]
 
 #[macro_use]

compiler/rustc_lint/src/types.rs

@@ -18,6 +18,7 @@ use rustc_target::abi::{Integer, LayoutOf, TagEncoding, VariantIdx, Variants};
 use rustc_target::spec::abi::Abi as SpecAbi;
 
 use std::cmp;
+use std::ops::ControlFlow;
 use tracing::debug;
 
 declare_lint! {
@@ -1135,11 +1136,11 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         };
 
         impl<'a, 'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueTypes<'a, 'tcx> {
-            fn visit_ty(&mut self, ty: Ty<'tcx>) -> bool {
+            fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<()> {
                 match ty.kind() {
                     ty::Opaque(..) => {
                         self.ty = Some(ty);
-                        true
+                        ControlFlow::BREAK
                     }
                     // Consider opaque types within projections FFI-safe if they do not normalize
                     // to more opaque types.
@@ -1148,7 +1149,11 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
 
                         // If `ty` is a opaque type directly then `super_visit_with` won't invoke
                         // this function again.
-                        if ty.has_opaque_types() { self.visit_ty(ty) } else { false }
+                        if ty.has_opaque_types() {
+                            self.visit_ty(ty)
+                        } else {
+                            ControlFlow::CONTINUE
+                        }
                     }
                     _ => ty.super_visit_with(self),
                 }

compiler/rustc_macros/src/type_foldable.rs

@@ -15,8 +15,12 @@ pub fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::
             }
         })
     });
-    let body_visit = s.fold(false, |acc, bind| {
-        quote! { #acc || ::rustc_middle::ty::fold::TypeFoldable::visit_with(#bind, __folder) }
+
+    let body_visit = s.fold(quote!(), |acc, bind| {
+        quote! {
+            #acc
+            ::rustc_middle::ty::fold::TypeFoldable::visit_with(#bind, __folder)?;
+        }
     });
 
     s.bound_impl(
@@ -32,8 +36,9 @@ pub fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::
             fn super_visit_with<__F: ::rustc_middle::ty::fold::TypeVisitor<'tcx>>(
                 &self,
                 __folder: &mut __F
-            ) -> bool {
+            ) -> ::std::ops::ControlFlow<()> {
                 match *self { #body_visit }
+                ::std::ops::ControlFlow::CONTINUE
             }
         },
     )

compiler/rustc_middle/src/lib.rs

@@ -49,6 +49,7 @@
 #![feature(int_error_matching)]
 #![feature(half_open_range_patterns)]
 #![feature(exclusive_range_pattern)]
+#![feature(control_flow_enum)]
 #![recursion_limit = "512"]
 
 #[macro_use]

compiler/rustc_middle/src/macros.rs

@@ -62,9 +62,9 @@ macro_rules! CloneTypeFoldableImpls {
                 fn super_visit_with<F: $crate::ty::fold::TypeVisitor<$tcx>>(
                     &self,
                     _: &mut F)
-                    -> bool
+                    -> ::std::ops::ControlFlow<()>
                 {
-                    false
+                    ::std::ops::ControlFlow::CONTINUE
                 }
             }
         )+
@@ -105,7 +105,7 @@ macro_rules! EnumTypeFoldableImpl {
             fn super_visit_with<V: $crate::ty::fold::TypeVisitor<$tcx>>(
                 &self,
                 visitor: &mut V,
-            ) -> bool {
+            ) -> ::std::ops::ControlFlow<()> {
                 EnumTypeFoldableImpl!(@VisitVariants(self, visitor) input($($variants)*) output())
             }
         }
@@ -179,9 +179,10 @@ macro_rules! EnumTypeFoldableImpl {
                 input($($input)*)
                 output(
                     $variant ( $($variant_arg),* ) => {
-                        false $(|| $crate::ty::fold::TypeFoldable::visit_with(
+                        $($crate::ty::fold::TypeFoldable::visit_with(
                             $variant_arg, $visitor
-                        ))*
+                        )?;)*
+                        ::std::ops::ControlFlow::CONTINUE
                     }
                     $($output)*
                 )
@@ -196,9 +197,10 @@ macro_rules! EnumTypeFoldableImpl {
                 input($($input)*)
                 output(
                     $variant { $($variant_arg),* } => {
-                        false $(|| $crate::ty::fold::TypeFoldable::visit_with(
+                        $($crate::ty::fold::TypeFoldable::visit_with(
                             $variant_arg, $visitor
-                        ))*
+                        )?;)*
+                        ::std::ops::ControlFlow::CONTINUE
                     }
                     $($output)*
                 )
@@ -212,7 +214,7 @@ macro_rules! EnumTypeFoldableImpl {
             @VisitVariants($this, $visitor)
                 input($($input)*)
                 output(
-                    $variant => { false }
+                    $variant => { ::std::ops::ControlFlow::CONTINUE }
                     $($output)*
                 )
         )

compiler/rustc_middle/src/mir/mod.rs

@@ -32,7 +32,7 @@ use rustc_target::abi;
 use rustc_target::asm::InlineAsmRegOrRegClass;
 use std::borrow::Cow;
 use std::fmt::{self, Debug, Display, Formatter, Write};
-use std::ops::{Index, IndexMut};
+use std::ops::{ControlFlow, Index, IndexMut};
 use std::slice;
 use std::{iter, mem, option};
 
@@ -2489,7 +2489,7 @@ impl<'tcx> TypeFoldable<'tcx> for UserTypeProjection {
         UserTypeProjection { base, projs }
     }
 
-    fn super_visit_with<Vs: TypeVisitor<'tcx>>(&self, visitor: &mut Vs) -> bool {
+    fn super_visit_with<Vs: TypeVisitor<'tcx>>(&self, visitor: &mut Vs) -> ControlFlow<()> {
         self.base.visit_with(visitor)
         // Note: there's nothing in `self.proj` to visit.
     }