diff options
| -rw-r--r-- | compiler/rustc_type_ir/src/fold.rs | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/compiler/rustc_type_ir/src/fold.rs b/compiler/rustc_type_ir/src/fold.rs index 68669694b32..e7a6831f5ee 100644 --- a/compiler/rustc_type_ir/src/fold.rs +++ b/compiler/rustc_type_ir/src/fold.rs @@ -51,6 +51,12 @@ use crate::{visit::TypeVisitable, Interner}; /// /// To implement this conveniently, use the derive macro located in /// `rustc_macros`. +/// +/// This trait is a sub-trait of `TypeVisitable`. This is because many +/// `TypeFolder` instances use the methods in `TypeVisitableExt` while folding, +/// which means in practice almost every foldable type needs to also be +/// visitable. (However, there are some types that are visitable without being +/// foldable.) pub trait TypeFoldable<I: Interner>: TypeVisitable<I> { /// The entry point for folding. To fold a value `t` with a folder `f` /// call: `t.try_fold_with(f)`. |