ecb867ec3c
Clarify `Layout` interning. `Layout` is another type that is sometimes interned, sometimes not, and we always use references to refer to it so we can't take any advantage of the uniqueness properties for hashing or equality checks. This commit renames `Layout` as `LayoutS`, and then introduces a new `Layout` that is a newtype around an `Interned<LayoutS>`. It also interns more layouts than before. Previously layouts within layouts (via the `variants` field) were never interned, but now they are. Hence the lifetime on the new `Layout` type. Unlike other interned types, these ones are in `rustc_target` instead of `rustc_middle`. This reflects the existing structure of the code, which does layout-specific stuff in `rustc_target` while `TyAndLayout` is generic over the `Ty`, allowing the type-specific stuff to occur in `rustc_middle`. The commit also adds a `HashStable` impl for `Interned`, which was needed. It hashes the contents, unlike the `Hash` impl which hashes the pointer. r? `@fee1-dead` |
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