Rename TypeFolderFallible to FallibleTypeFolder

compiler/rustc_infer/src/infer/resolve.rs

 use super::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use super::{FixupError, FixupResult, InferCtxt, Span};
 use rustc_middle::mir;
-use rustc_middle::ty::fold::{TypeFolder, TypeFolderFallible, TypeVisitor};
+use rustc_middle::ty::fold::{FallibleTypeFolder, TypeFolder, TypeVisitor};
 use rustc_middle::ty::{self, Const, InferConst, Ty, TyCtxt, TypeFoldable};
 
 use std::ops::ControlFlow;
@@ -192,7 +192,7 @@ fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
     }
 }
 
-impl<'a, 'tcx> TypeFolderFallible<'tcx> for FullTypeResolver<'a, 'tcx> {
+impl<'a, 'tcx> FallibleTypeFolder<'tcx> for FullTypeResolver<'a, 'tcx> {
     fn try_fold_ty(&mut self, t: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> {
         if !t.needs_infer() {
             Ok(t) // micro-optimize -- if there is nothing in this type that this fold affects...

compiler/rustc_infer/src/traits/structural_impls.rs

 use crate::traits;
 use crate::traits::project::Normalized;
 use rustc_middle::ty;
-use rustc_middle::ty::fold::{TypeFoldable, TypeFolderFallible, TypeVisitor};
+use rustc_middle::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeVisitor};
 
 use std::fmt;
 use std::ops::ControlFlow;
@@ -60,7 +60,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 // TypeFoldable implementations.
 
 impl<'tcx, O: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::Obligation<'tcx, O> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {

compiler/rustc_macros/src/type_foldable.rs

@@ -25,7 +25,7 @@ pub fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::
     s.bound_impl(
         quote!(::rustc_middle::ty::fold::TypeFoldable<'tcx>),
         quote! {
-            fn try_super_fold_with<__F: ::rustc_middle::ty::fold::TypeFolderFallible<'tcx>>(
+            fn try_super_fold_with<__F: ::rustc_middle::ty::fold::FallibleTypeFolder<'tcx>>(
                 self,
                 __folder: &mut __F
             ) -> Result<Self, __F::Error> {

compiler/rustc_middle/src/macros.rs

@@ -52,7 +52,7 @@ fn lift_to_tcx(self, _: $crate::ty::TyCtxt<$tcx>) -> Option<Self> {
     (for <$tcx:lifetime> { $($ty:ty,)+ }) => {
         $(
             impl<$tcx> $crate::ty::fold::TypeFoldable<$tcx> for $ty {
-                fn try_super_fold_with<F: $crate::ty::fold::TypeFolderFallible<$tcx>>(
+                fn try_super_fold_with<F: $crate::ty::fold::FallibleTypeFolder<$tcx>>(
                     self,
                     _: &mut F
                 ) -> ::std::result::Result<$ty, F::Error> {
@@ -95,7 +95,7 @@ fn super_visit_with<F: $crate::ty::fold::TypeVisitor<$tcx>>(
         impl<$($p),*> $crate::ty::fold::TypeFoldable<$tcx> for $s
             $(where $($wc)*)*
         {
-            fn try_super_fold_with<V: $crate::ty::fold::TypeFolderFallible<$tcx>>(
+            fn try_super_fold_with<V: $crate::ty::fold::FallibleTypeFolder<$tcx>>(
                 self,
                 folder: &mut V,
             ) -> ::std::result::Result<Self, V::Error> {

compiler/rustc_middle/src/mir/mod.rs

@@ -7,7 +7,7 @@
 use crate::mir::visit::MirVisitable;
 use crate::ty::adjustment::PointerCast;
 use crate::ty::codec::{TyDecoder, TyEncoder};
-use crate::ty::fold::{TypeFoldable, TypeFolderFallible, TypeVisitor};
+use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeVisitor};
 use crate::ty::print::{FmtPrinter, Printer};
 use crate::ty::subst::{Subst, SubstsRef};
 use crate::ty::{self, List, Ty, TyCtxt};
@@ -2760,7 +2760,7 @@ pub(crate) fn variant(
 TrivialTypeFoldableAndLiftImpls! { ProjectionKind, }
 
 impl<'tcx> TypeFoldable<'tcx> for UserTypeProjection {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {

compiler/rustc_middle/src/mir/type_foldable.rs

@@ -16,7 +16,7 @@
 }
 
 impl<'tcx> TypeFoldable<'tcx> for Terminator<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -148,7 +148,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx> TypeFoldable<'tcx> for GeneratorKind {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(self, _: &mut F) -> Result<Self, F::Error> {
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(self, _: &mut F) -> Result<Self, F::Error> {
         Ok(self)
     }
 
@@ -158,7 +158,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _: &mut V) -> ControlFlow<V::Br
 }
 
 impl<'tcx> TypeFoldable<'tcx> for Place<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -175,7 +175,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<PlaceElem<'tcx>> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -188,7 +188,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx> TypeFoldable<'tcx> for Rvalue<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -292,7 +292,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx> TypeFoldable<'tcx> for Operand<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -312,7 +312,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx> TypeFoldable<'tcx> for PlaceElem<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -345,7 +345,7 @@ fn super_visit_with<Vs: TypeVisitor<'tcx>>(
 }
 
 impl<'tcx> TypeFoldable<'tcx> for Field {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(self, _: &mut F) -> Result<Self, F::Error> {
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(self, _: &mut F) -> Result<Self, F::Error> {
         Ok(self)
     }
     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _: &mut V) -> ControlFlow<V::BreakTy> {
@@ -354,7 +354,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _: &mut V) -> ControlFlow<V::Br
 }
 
 impl<'tcx> TypeFoldable<'tcx> for GeneratorSavedLocal {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(self, _: &mut F) -> Result<Self, F::Error> {
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(self, _: &mut F) -> Result<Self, F::Error> {
         Ok(self)
     }
     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _: &mut V) -> ControlFlow<V::BreakTy> {
@@ -363,7 +363,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _: &mut V) -> ControlFlow<V::Br
 }
 
 impl<'tcx, R: Idx, C: Idx> TypeFoldable<'tcx> for BitMatrix<R, C> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(self, _: &mut F) -> Result<Self, F::Error> {
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(self, _: &mut F) -> Result<Self, F::Error> {
         Ok(self)
     }
     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _: &mut V) -> ControlFlow<V::BreakTy> {
@@ -372,7 +372,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _: &mut V) -> ControlFlow<V::Br
 }
 
 impl<'tcx> TypeFoldable<'tcx> for Constant<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -390,11 +390,11 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 
 impl<'tcx> TypeFoldable<'tcx> for ConstantKind<'tcx> {
     #[inline(always)]
-    fn try_fold_with<F: TypeFolderFallible<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
         folder.try_fold_mir_const(self)
     }
 
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {

compiler/rustc_middle/src/ty/fold.rs

@@ -63,12 +63,12 @@ fn fold_with<F: TypeFolder<'tcx, Error = !>>(self, folder: &mut F) -> Self {
         self.try_fold_with(folder).into_ok()
     }
 
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error>;
 
-    fn try_fold_with<F: TypeFolderFallible<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
         self.try_super_fold_with(folder)
     }
 
@@ -216,8 +216,8 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _: &mut V) -> ControlFlow<V::Br
 ///
 /// If this folder is fallible (and therefore its [`Error`][`TypeFolder::Error`]
 /// associated type is something other than the default, never),
-/// [`TypeFolderFallible`] should be implemented manually; otherwise,
-/// a blanket implementation of [`TypeFolderFallible`] will defer to
+/// [`FallibleTypeFolder`] should be implemented manually; otherwise,
+/// a blanket implementation of [`FallibleTypeFolder`] will defer to
 /// the infallible methods of this trait to ensure that the two APIs
 /// are coherent.
 pub trait TypeFolder<'tcx>: Sized {
@@ -269,7 +269,7 @@ fn fold_mir_const(&mut self, c: mir::ConstantKind<'tcx>) -> mir::ConstantKind<'t
     }
 }
 
-/// The `TypeFolderFallible` trait defines the actual *folding*. There is a
+/// The `FallibleTypeFolder` trait defines the actual *folding*. There is a
 /// method defined for every foldable type. Each of these has a
 /// default implementation that does an "identity" fold. Within each
 /// identity fold, it should invoke `foo.try_fold_with(self)` to fold each
@@ -278,7 +278,7 @@ fn fold_mir_const(&mut self, c: mir::ConstantKind<'tcx>) -> mir::ConstantKind<'t
 /// A blanket implementation of this trait (that defers to the relevant
 /// method of [`TypeFolder`]) is provided for all infallible folders in
 /// order to ensure the two APIs are coherent.
-pub trait TypeFolderFallible<'tcx>: TypeFolder<'tcx> {
+pub trait FallibleTypeFolder<'tcx>: TypeFolder<'tcx> {
     fn try_fold_binder<T>(&mut self, t: Binder<'tcx, T>) -> Result<Binder<'tcx, T>, Self::Error>
     where
         T: TypeFoldable<'tcx>,
@@ -318,7 +318,7 @@ fn try_fold_mir_const(
 
 // Blanket implementation of fallible trait for infallible folders
 // delegates to infallible methods to prevent incoherence
-impl<'tcx, F> TypeFolderFallible<'tcx> for F
+impl<'tcx, F> FallibleTypeFolder<'tcx> for F
 where
     F: TypeFolder<'tcx, Error = !>,
 {

compiler/rustc_middle/src/ty/mod.rs

@@ -9,7 +9,7 @@
 //!
 //! ["The `ty` module: representing types"]: https://rustc-dev-guide.rust-lang.org/ty.html
 
-pub use self::fold::{TypeFoldable, TypeFolder, TypeFolderFallible, TypeVisitor};
+pub use self::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder, TypeVisitor};
 pub use self::AssocItemContainer::*;
 pub use self::BorrowKind::*;
 pub use self::IntVarValue::*;
@@ -1269,7 +1269,7 @@ fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHas
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ParamEnv<'tcx> {
-    fn try_super_fold_with<F: ty::fold::TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: ty::fold::FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -4,7 +4,7 @@
 
 use crate::mir::interpret;
 use crate::mir::ProjectionKind;
-use crate::ty::fold::{TypeFoldable, TypeFolderFallible, TypeVisitor};
+use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeVisitor};
 use crate::ty::print::{with_no_trimmed_paths, FmtPrinter, Printer};
 use crate::ty::{self, InferConst, Lift, Ty, TyCtxt};
 use rustc_data_structures::functor::IdFunctor;
@@ -669,7 +669,7 @@ fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 
 /// AdtDefs are basically the same as a DefId.
 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::AdtDef {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         _folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -682,7 +682,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlo
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>, U: TypeFoldable<'tcx>> TypeFoldable<'tcx> for (T, U) {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<(T, U), F::Error> {
@@ -698,7 +698,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 impl<'tcx, A: TypeFoldable<'tcx>, B: TypeFoldable<'tcx>, C: TypeFoldable<'tcx>> TypeFoldable<'tcx>
     for (A, B, C)
 {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<(A, B, C), F::Error> {
@@ -731,7 +731,7 @@ impl<'tcx, T, E> TypeFoldable<'tcx> for Result<T, E> {
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Rc<T> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -745,7 +745,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Arc<T> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -759,7 +759,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<T> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -772,7 +772,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Vec<T> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -785,7 +785,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<[T]> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -798,14 +798,14 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::Binder<'tcx, T> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
         self.try_map_bound(|ty| ty.try_fold_with(folder))
     }
 
-    fn try_fold_with<F: TypeFolderFallible<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
         folder.try_fold_binder(self)
     }
 
@@ -819,7 +819,7 @@ fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::Br
 }
 
 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -832,7 +832,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<Ty<'tcx>> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -845,7 +845,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ProjectionKind> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -858,7 +858,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::instance::Instance<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -909,7 +909,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx> TypeFoldable<'tcx> for interpret::GlobalId<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -922,7 +922,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx> TypeFoldable<'tcx> for Ty<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -966,7 +966,7 @@ fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
         Ok(if *self.kind() == kind { self } else { folder.tcx().mk_ty(kind) })
     }
 
-    fn try_fold_with<F: TypeFolderFallible<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
         folder.try_fold_ty(self)
     }
 
@@ -1018,14 +1018,14 @@ fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::Br
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::Region<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         _folder: &mut F,
     ) -> Result<Self, F::Error> {
         Ok(self)
     }
 
-    fn try_fold_with<F: TypeFolderFallible<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
         folder.try_fold_region(self)
     }
 
@@ -1039,11 +1039,11 @@ fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::Br
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::Predicate<'tcx> {
-    fn try_fold_with<F: TypeFolderFallible<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
         folder.try_fold_predicate(self)
     }
 
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -1069,7 +1069,7 @@ fn has_type_flags(&self, flags: ty::TypeFlags) -> bool {
 }
 
 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Predicate<'tcx>> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -1082,7 +1082,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>, I: Idx> TypeFoldable<'tcx> for IndexVec<I, T> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -1095,7 +1095,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Const<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -1108,7 +1108,7 @@ fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
         }
     }
 
-    fn try_fold_with<F: TypeFolderFallible<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
         folder.try_fold_const(self)
     }
 
@@ -1123,7 +1123,7 @@ fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::Br
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::ConstKind<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -1152,7 +1152,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx> TypeFoldable<'tcx> for InferConst<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         _folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -1165,7 +1165,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlo
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::Unevaluated<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -1193,7 +1193,7 @@ fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::Unevaluated<'tcx, ()> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {

compiler/rustc_middle/src/ty/subst.rs

@@ -2,7 +2,7 @@
 
 use crate::mir;
 use crate::ty::codec::{TyDecoder, TyEncoder};
-use crate::ty::fold::{TypeFoldable, TypeFolder, TypeFolderFallible, TypeVisitor};
+use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder, TypeVisitor};
 use crate::ty::sty::{ClosureSubsts, GeneratorSubsts, InlineConstSubsts};
 use crate::ty::{self, Lift, List, ParamConst, Ty, TyCtxt};
 
@@ -153,7 +153,7 @@ fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 }
 
 impl<'tcx> TypeFoldable<'tcx> for GenericArg<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -375,7 +375,7 @@ pub fn truncate_to(&self, tcx: TyCtxt<'tcx>, generics: &ty::Generics) -> SubstsR
 }
 
 impl<'tcx> TypeFoldable<'tcx> for SubstsRef<'tcx> {
-    fn try_super_fold_with<F: TypeFolderFallible<'tcx>>(
+    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {

compiler/rustc_middle/src/ty/util.rs

 //! Miscellaneous type-system utilities that are too small to deserve their own modules.
 
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
-use crate::ty::fold::{TypeFolder, TypeFolderFallible};
+use crate::ty::fold::{FallibleTypeFolder, TypeFolder};
 use crate::ty::layout::IntegerExt;
 use crate::ty::query::TyCtxtAt;
 use crate::ty::subst::{GenericArgKind, Subst, SubstsRef};
@@ -1048,7 +1048,7 @@ pub fn fold_list<'tcx, F, T>(
     intern: impl FnOnce(TyCtxt<'tcx>, &[T]) -> &'tcx ty::List<T>,
 ) -> Result<&'tcx ty::List<T>, F::Error>
 where
-    F: TypeFolderFallible<'tcx>,
+    F: FallibleTypeFolder<'tcx>,
     T: TypeFoldable<'tcx> + PartialEq + Copy,
 {
     let mut iter = list.iter();

compiler/rustc_trait_selection/src/traits/query/normalize.rs

@@ -12,7 +12,7 @@
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_infer::traits::Normalized;
 use rustc_middle::mir;
-use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeFolderFallible};
+use rustc_middle::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder};
 use rustc_middle::ty::subst::Subst;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitor};
 
@@ -178,7 +178,7 @@ fn tcx<'c>(&'c self) -> TyCtxt<'tcx> {
     }
 }
 
-impl<'cx, 'tcx> TypeFolderFallible<'tcx> for QueryNormalizer<'cx, 'tcx> {
+impl<'cx, 'tcx> FallibleTypeFolder<'tcx> for QueryNormalizer<'cx, 'tcx> {
     fn try_fold_binder<T: TypeFoldable<'tcx>>(
         &mut self,
         t: ty::Binder<'tcx, T>,