diff --git a/src/ty-fold.md b/src/ty-fold.md index f659612e..d413e503 100644 --- a/src/ty-fold.md +++ b/src/ty-fold.md @@ -1,8 +1,10 @@ # `TypeFoldable` and `TypeFolder` -In [a previous chapter], we discussed instantiating binders. This involves looking at everything inside of a `Early(Binder)` -to find any usages of the bound vars in order to replace them. Binders can wrap an arbitrary Rust type `T`, not just a `Ty`. So, -how do we implement the `instantiate` methods on the `Early/Binder` types. +In [a previous chapter], we discussed instantiating binders. +This involves looking at everything inside of a `Early(Binder)` +to find any usages of the bound vars in order to replace them. +Binders can wrap an arbitrary Rust type `T`, not just a `Ty`. +So, how do we implement the `instantiate` methods on the `Early/Binder` types. The answer is a couple of traits: [`TypeFoldable`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/fold/trait.TypeFoldable.html)