Rename folding/visiting traits

book/src/SUMMARY.md

@@ -12,7 +12,7 @@
         - [Application types](./types/rust_types/application_ty.md)
     - [Rust lifetimes](./types/rust_lifetimes.md)
     - [Operations](./types/operations.md)
-        - [Fold and the Folder trait](./types/operations/fold.md)
+        - [TypeFoldable and the TypeFolder trait](./types/operations/fold.md)
 - [Lowering Rust IR to logic](./clauses.md)
     - [Goals and clauses](./clauses/goals_and_clauses.md)
     - [Type equality and unification](./clauses/type_equality.md)

book/src/types/operations/fold.md

@@ -1,64 +1,64 @@
-# Fold and the Folder trait
+# TypeFoldable and the TypeFolder trait
 
-The [`Fold`] trait permits one to traverse a type or other term in the
+The [`TypeFoldable`] trait permits one to traverse a type or other term in the
 chalk-ir and make a copy of it, possibly making small substitutions or
 alterations along the way. Folding also allows copying a term from one
 interner to another.
 
-[`Fold`]: https://rust-lang.github.io/chalk/chalk_ir/fold/trait.Fold.html
+[`TypeFoldable`]: https://rust-lang.github.io/chalk/chalk_ir/fold/trait.TypeFoldable.html
 
-To use the [`Fold`] trait, one invokes the [`Fold::fold_with`] method, supplying some
+To use the [`TypeFoldable`] trait, one invokes the [`TypeFoldable::fold_with`] method, supplying some
 "folder" as well as the number of "in scope binders" for that term (typically `0`
 to start):
 
 ```rust,ignore
 let output_ty = input_ty.fold_with(&mut folder, 0);
 ```
 
-[`Fold::fold_with`]: https://rust-lang.github.io/chalk/chalk_ir/fold/trait.Fold.html#tymethod.fold_with
+[`TypeFoldable::fold_with`]: https://rust-lang.github.io/chalk/chalk_ir/fold/trait.TypeFoldable.html#tymethod.fold_with
 
-The folder is some instance of the [`Folder`] trait. This trait
+The folder is some instance of the [`TypeFolder`] trait. This trait
 defines a few key callbacks that allow you to substitute different
 values as the fold proceeds. For example, when a type is folded, the
 folder can substitute a new type in its place.
 
-[`Folder`]: https://rust-lang.github.io/chalk/chalk_ir/fold/trait.Folder.html
+[`TypeFolder`]: https://rust-lang.github.io/chalk/chalk_ir/fold/trait.TypeFolder.html
 
 ## Uses for folders
 
-A common use for `Fold` is to permit a substitution -- that is,
+A common use for `TypeFoldable` is to permit a substitution -- that is,
 replacing generic type parameters with their values.
 
-## From Fold to Folder to SuperFold and back again
+## From TypeFoldable to TypeFolder to TypeSuperFoldable and back again
 
 The overall flow of folding is like this.
 
-1. [`Fold::fold_with`] is invoked on the outermost term. It recursively
+1. [`TypeFoldable::fold_with`] is invoked on the outermost term. It recursively
    walks the term.
 2. For those sorts of terms (types, lifetimes, goals, program clauses) that have
-   callbacks in the [`Folder`] trait, invoking [`Fold::fold_with`] will in turn
-   invoke the corresponding method on the [`Folder`] trait, such as `Folder::fold_ty`.
-3. The default implementation of `Folder::fold_ty`, in turn, invokes
-   `SuperFold::super_fold_with`.  This will recursively fold the
+   callbacks in the [`TypeFolder`] trait, invoking [`TypeFoldable::fold_with`] will in turn
+   invoke the corresponding method on the [`TypeFolder`] trait, such as `TypeFolder::fold_ty`.
+3. The default implementation of `TypeFolder::fold_ty`, in turn, invokes
+   `TypeSuperFoldable::super_fold_with`.  This will recursively fold the
    contents of the type. In some cases, the `super_fold_with`
-   implementation invokes more specialized methods on [`Folder`], such
-   as [`Folder::fold_free_var_ty`], which makes it easier to write
+   implementation invokes more specialized methods on [`TypeFolder`], such
+   as [`TypeFolder::fold_free_var_ty`], which makes it easier to write
    folders that just intercept *certain* types.
 
-[`Folder::fold_free_var_ty`]: https://rust-lang.github.io/chalk/chalk_ir/fold/trait.Folder.html#method.fold_free_var_ty
+[`TypeFolder::fold_free_var_ty`]: https://rust-lang.github.io/chalk/chalk_ir/fold/trait.TypeFolder.html#method.fold_free_var_ty
 
 Thus, as a user, you can customize folding by:
 
-* Defining your own `Folder` type
+* Defining your own `TypeFolder` type
 * Implementing the appropriate methods to "intercept" types/lifetimes/etc at the right level of
   detail
 * In those methods, if you find a case where you would prefer not to
-  substitute a new value, then invoke `SuperFold::super_fold_with` to
+  substitute a new value, then invoke `TypeSuperFoldable::super_fold_with` to
   return to the default behavior.
 
 ## The `binders` argument
 
-Each callback in the [`Folder`] trait takes a `binders` argument. This indicates
+Each callback in the [`TypeFolder`] trait takes a `binders` argument. This indicates
 the number of binders that we have traversed during folding, which is relevant for De Bruijn indices.
 So e.g. a bound variable with depth 1, if invoked with a `binders` value of 1, indicates something that was bound to something external to the fold.
 
@@ -70,32 +70,32 @@ Foo<'a>: for<'b> Bar<'b>
 
 In this case, `Foo<'a>` gets visited with depth 0 and `Bar<'b>` gets visited with depth 1.
 
-## The `Fold::Result` associated type
+## The `TypeFoldable::Result` associated type
 
-The `Fold` trait defines a [`Result`] associated type, indicating the
+The `TypeFoldable` trait defines a [`Result`] associated type, indicating the
 type that will result from folding.
 
-[`Result`]: https://rust-lang.github.io/chalk/chalk_ir/fold/trait.Fold.html#associatedtype.Result
+[`Result`]: https://rust-lang.github.io/chalk/chalk_ir/fold/trait.TypeFoldable.html#associatedtype.Result
 
-## When to implement the Fold and SuperFold traits
+## When to implement the TypeFoldable and TypeSuperFoldable traits
 
 Any piece of IR that represents a kind of "term" (e.g., a type, part
-of a type, or a goal, etc) in the logic should implement `Fold`. We
-also implement `Fold` for common collection types like `Vec` as well
+of a type, or a goal, etc) in the logic should implement `TypeFoldable`. We
+also implement `TypeFoldable` for common collection types like `Vec` as well
 as tuples, references, etc.
 
-The `SuperFold` trait should only be implemented for those types that
-have a callback defined on the `Folder` trait (e.g., types and
+The `TypeSuperFoldable` trait should only be implemented for those types that
+have a callback defined on the `TypeFolder` trait (e.g., types and
 lifetimes).
 
 ## Derives
 
-Using the `chalk-derive` crate, you can auto-derive the `Fold` trait.
-There isn't presently a derive for `SuperFold` since it is very rare
-to require it. The derive for `Fold` is a bit cludgy and requires:
+Using the `chalk-derive` crate, you can auto-derive the `TypeFoldable` trait.
+There isn't presently a derive for `TypeSuperFoldable` since it is very rare
+to require it. The derive for `TypeFoldable` is a bit cludgy and requires:
 
-* You must import `Fold` into scope.
-* The type you are deriving `Fold` on must have either:
+* You must import `TypeFoldable` into scope.
+* The type you are deriving `TypeFoldable` on must have either:
   * A type parameter that has a `Interner` bound, like `I: Interner`
   * A type parameter that has a `HasInterner` bound, like `I: HasInterner`
   * The `has_interner(XXX)` attribute.

book/src/what_is_chalk/crates.md

@@ -19,7 +19,7 @@ The following crate is an implementation detail, used internally by `chalk-solve
 
 * The `chalk-engine` crate, which defines the actual engine that solves logical predicate. This
   engine is quite general and not really specific to Rust.
-* The `chalk-derive` crate defines custom derives for the `chalk_ir::fold::Fold` trait and other
+* The `chalk-derive` crate defines custom derives for the `chalk_ir::fold::TypeFoldable` trait and other
   such things.
 
 ## Crates for standalone REPL and testing
@@ -37,11 +37,11 @@ define a kind of "minimal embedding" of chalk.
 
 ## The chalk-solve crate
 
-| The `chalk-solve` crate | |
-|---|--- |
-| Purpose:  | to solve a given goal |
-| Depends on IR:  | chalk-ir and rust-ir   |
-| Context required:  | `RustIrDatabase` |
+| The `chalk-solve` crate |                       |
+| ----------------------- | --------------------- |
+| Purpose:                | to solve a given goal |
+| Depends on IR:          | chalk-ir and rust-ir  |
+| Context required:       | `RustIrDatabase`      |
 
 The `chalk-solve` crate exposes a key type called `Solver`.  This is a
 solver that, given a goal (expressed in chalk-ir) will solve the goal
@@ -60,11 +60,11 @@ provide needed context for the solver -- notably, the solver can ask:
 
 ## The chalk-engine crate
 
-| The `chalk-engine` crate  |   |
-|---|--- |
-| Purpose:  | define the base solving strategy |
-| IR:  | none   |
-| Context required:  | `Context` trait |
+| The `chalk-engine` crate |                                  |
+| ------------------------ | -------------------------------- |
+| Purpose:                 | define the base solving strategy |
+| IR:                      | none                             |
+| Context required:        | `Context` trait                  |
 
 For the purposes of chalk, the `chalk-engine` crate is effectively
 encapsulated by `chalk-solve`.  It defines the base SLG engine. It is

chalk-derive/src/lib.rs

@@ -118,9 +118,9 @@ enum DeriveKind {
 }
 
 decl_derive!([HasInterner, attributes(has_interner)] => derive_has_interner);
-decl_derive!([Visit, attributes(has_interner)] => derive_visit);
-decl_derive!([SuperVisit, attributes(has_interner)] => derive_super_visit);
-decl_derive!([Fold, attributes(has_interner)] => derive_fold);
+decl_derive!([TypeVisitable, attributes(has_interner)] => derive_type_visitable);
+decl_derive!([TypeSuperVisitable, attributes(has_interner)] => derive_type_super_visitable);
+decl_derive!([TypeFoldable, attributes(has_interner)] => derive_type_foldable);
 decl_derive!([Zip, attributes(has_interner)] => derive_zip);
 
 fn derive_has_interner(mut s: synstructure::Structure) -> TokenStream {
@@ -136,24 +136,28 @@ fn derive_has_interner(mut s: synstructure::Structure) -> TokenStream {
     )
 }
 
-/// Derives Visit for structs and enums for which one of the following is true:
+/// Derives TypeVisitable for structs and enums for which one of the following is true:
 /// - It has a `#[has_interner(TheInterner)]` attribute
 /// - There is a single parameter `T: HasInterner` (does not have to be named `T`)
 /// - There is a single parameter `I: Interner` (does not have to be named `I`)
-fn derive_visit(s: synstructure::Structure) -> TokenStream {
-    derive_any_visit(s, parse_quote! { Visit }, parse_quote! { visit_with })
+fn derive_type_visitable(s: synstructure::Structure) -> TokenStream {
+    derive_any_type_visitable(
+        s,
+        parse_quote! { TypeVisitable },
+        parse_quote! { visit_with },
+    )
 }
 
-/// Same as Visit, but derives SuperVisit instead
-fn derive_super_visit(s: synstructure::Structure) -> TokenStream {
-    derive_any_visit(
+/// Same as TypeVisitable, but derives TypeSuperVisitable instead
+fn derive_type_super_visitable(s: synstructure::Structure) -> TokenStream {
+    derive_any_type_visitable(
         s,
-        parse_quote! { SuperVisit },
+        parse_quote! { TypeSuperVisitable },
         parse_quote! { super_visit_with },
     )
 }
 
-fn derive_any_visit(
+fn derive_any_type_visitable(
     mut s: synstructure::Structure,
     trait_name: Ident,
     method_name: Ident,
@@ -164,13 +168,13 @@ fn derive_any_visit(
 
     let body = s.each(|bi| {
         quote! {
-            ::chalk_ir::try_break!(::chalk_ir::visit::Visit::visit_with(#bi, visitor, outer_binder));
+            ::chalk_ir::try_break!(::chalk_ir::visit::TypeVisitable::visit_with(#bi, visitor, outer_binder));
         }
     });
 
     if kind == DeriveKind::FromHasInterner {
         let param = get_generic_param_name(input).unwrap();
-        s.add_where_predicate(parse_quote! { #param: ::chalk_ir::visit::Visit<#interner> });
+        s.add_where_predicate(parse_quote! { #param: ::chalk_ir::visit::TypeVisitable<#interner> });
     }
 
     s.add_bounds(synstructure::AddBounds::None);
@@ -179,7 +183,7 @@ fn derive_any_visit(
         quote! {
             fn #method_name <B>(
                 &self,
-                visitor: &mut dyn ::chalk_ir::visit::Visitor < #interner, BreakTy = B >,
+                visitor: &mut dyn ::chalk_ir::visit::TypeVisitor < #interner, BreakTy = B >,
                 outer_binder: ::chalk_ir::DebruijnIndex,
             ) -> std::ops::ControlFlow<B> {
                 match *self {
@@ -250,11 +254,11 @@ fn derive_zip(mut s: synstructure::Structure) -> TokenStream {
     )
 }
 
-/// Derives Fold for structs and enums for which one of the following is true:
+/// Derives TypeFoldable for structs and enums for which one of the following is true:
 /// - It has a `#[has_interner(TheInterner)]` attribute
 /// - There is a single parameter `T: HasInterner` (does not have to be named `T`)
 /// - There is a single parameter `I: Interner` (does not have to be named `I`)
-fn derive_fold(mut s: synstructure::Structure) -> TokenStream {
+fn derive_type_foldable(mut s: synstructure::Structure) -> TokenStream {
     s.underscore_const(true);
     s.bind_with(|_| synstructure::BindStyle::Move);
 
@@ -265,7 +269,7 @@ fn derive_fold(mut s: synstructure::Structure) -> TokenStream {
         vi.construct(|_, index| {
             let bind = &bindings[index];
             quote! {
-                ::chalk_ir::fold::Fold::fold_with(#bind, folder, outer_binder)?
+                ::chalk_ir::fold::TypeFoldable::fold_with(#bind, folder, outer_binder)?
             }
         })
     });
@@ -277,7 +281,7 @@ fn derive_fold(mut s: synstructure::Structure) -> TokenStream {
         let param = get_generic_param_name(input).unwrap();
         s.add_impl_generic(parse_quote! { _U })
             .add_where_predicate(
-                parse_quote! { #param: ::chalk_ir::fold::Fold<#interner, Result = _U> },
+                parse_quote! { #param: ::chalk_ir::fold::TypeFoldable<#interner, Result = _U> },
             )
             .add_where_predicate(
                 parse_quote! { _U: ::chalk_ir::interner::HasInterner<Interner = #interner> },
@@ -289,13 +293,13 @@ fn derive_fold(mut s: synstructure::Structure) -> TokenStream {
 
     s.add_bounds(synstructure::AddBounds::None);
     s.bound_impl(
-        quote!(::chalk_ir::fold::Fold<#interner>),
+        quote!(::chalk_ir::fold::TypeFoldable<#interner>),
         quote! {
             type Result = #result;
 
             fn fold_with<E>(
                 self,
-                folder: &mut dyn ::chalk_ir::fold::Folder < #interner, Error = E >,
+                folder: &mut dyn ::chalk_ir::fold::TypeFolder < #interner, Error = E >,
                 outer_binder: ::chalk_ir::DebruijnIndex,
             ) -> ::std::result::Result<Self::Result, E> {
                 Ok(match self { #body })

chalk-engine/src/lib.rs

@@ -56,7 +56,7 @@
 use std::cmp::min;
 use std::usize;
 
-use chalk_derive::{Fold, HasInterner, Visit};
+use chalk_derive::{HasInterner, TypeFoldable, TypeVisitable};
 use chalk_ir::interner::Interner;
 use chalk_ir::{
     AnswerSubst, Canonical, ConstrainedSubst, Constraint, DebruijnIndex, Goal, InEnvironment,
@@ -78,13 +78,13 @@ mod table;
 mod tables;
 
 index_struct! {
-    pub struct TableIndex { // FIXME: pub b/c Fold
+    pub struct TableIndex { // FIXME: pub b/c TypeFoldable
         value: usize,
     }
 }
 
 /// The paper describes these as `A :- D | G`.
-#[derive(Clone, Debug, PartialEq, Eq, Hash, Fold, Visit, HasInterner)]
+#[derive(Clone, Debug, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable, HasInterner)]
 pub struct ExClause<I: Interner> {
     /// The substitution which, applied to the goal of our table,
     /// would yield A.
@@ -168,7 +168,7 @@ impl TimeStamp {
 ///
 /// trying to solve `?T: Foo` would immediately require solving `?T:
 /// Sized`, and hence would flounder.
-#[derive(Clone, Debug, PartialEq, Eq, Hash, Fold, Visit)]
+#[derive(Clone, Debug, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable)]
 pub struct FlounderedSubgoal<I: Interner> {
     /// Literal that floundered.
     pub floundered_literal: Literal<I>,
@@ -209,7 +209,7 @@ pub struct CompleteAnswer<I: Interner> {
 }
 
 /// Either `A` or `~A`, where `A` is a `Env |- Goal`.
-#[derive(Clone, Debug, Fold, Visit)]
+#[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
 pub enum Literal<I: Interner> {
     // FIXME: pub b/c fold
     Positive(InEnvironment<Goal<I>>),

chalk-engine/src/normalize_deep.rs

@@ -1,5 +1,5 @@
 use chalk_ir::fold::shift::Shift;
-use chalk_ir::fold::{Fold, Folder};
+use chalk_ir::fold::{TypeFoldable, TypeFolder};
 use chalk_ir::interner::Interner;
 use chalk_ir::*;
 use chalk_solve::infer::InferenceTable;
@@ -21,7 +21,7 @@ impl<I: Interner> DeepNormalizer<'_, I> {
     /// See also `InferenceTable::canonicalize`, which -- during real
     /// processing -- is often used to capture the "current state" of
     /// variables.
-    pub fn normalize_deep<T: Fold<I>>(
+    pub fn normalize_deep<T: TypeFoldable<I>>(
         table: &mut InferenceTable<I>,
         interner: I,
         value: T,
@@ -35,10 +35,10 @@ impl<I: Interner> DeepNormalizer<'_, I> {
     }
 }
 
-impl<I: Interner> Folder<I> for DeepNormalizer<'_, I> {
+impl<I: Interner> TypeFolder<I> for DeepNormalizer<'_, I> {
     type Error = NoSolution;
 
-    fn as_dyn(&mut self) -> &mut dyn Folder<I, Error = Self::Error> {
+    fn as_dyn(&mut self) -> &mut dyn TypeFolder<I, Error = Self::Error> {
         self
     }
 

chalk-engine/src/slg/resolvent.rs

@@ -3,7 +3,7 @@ use crate::slg::ResolventOps;
 use crate::{ExClause, Literal, TimeStamp};
 use chalk_ir::cast::Caster;
 use chalk_ir::fold::shift::Shift;
-use chalk_ir::fold::Fold;
+use chalk_ir::fold::TypeFoldable;
 use chalk_ir::interner::{HasInterner, Interner};
 use chalk_ir::zip::{Zip, Zipper};
 use chalk_ir::*;
@@ -708,7 +708,7 @@ impl<'i, I: Interner> Zipper<I> for AnswerSubstitutor<'i, I> {
         pending: &Binders<T>,
     ) -> Fallible<()>
     where
-        T: HasInterner<Interner = I> + Zip<I> + Fold<I, Result = T>,
+        T: HasInterner<Interner = I> + Zip<I> + TypeFoldable<I, Result = T>,
     {
         self.outer_binder.shift_in();
         Zip::zip_with(