Nicholas Nethercote 90db033955 Folding revamp. ... This commit makes type folding more like the way chalk does it. Currently, `TypeFoldable` has `fold_with` and `super_fold_with` methods. - `fold_with` is the standard entry point, and defaults to calling `super_fold_with`. - `super_fold_with` does the actual work of traversing a type. - For a few types of interest (`Ty`, `Region`, etc.) `fold_with` instead calls into a `TypeFolder`, which can then call back into `super_fold_with`. With the new approach, `TypeFoldable` has `fold_with` and `TypeSuperFoldable` has `super_fold_with`. - `fold_with` is still the standard entry point, *and* it does the actual work of traversing a type, for all types except types of interest. - `super_fold_with` is only implemented for the types of interest. Benefits of the new model. - I find it easier to understand. The distinction between types of interest and other types is clearer, and `super_fold_with` doesn't exist for most types. - With the current model is easy to get confused and implement a `super_fold_with` method that should be left defaulted. (Some of the precursor commits fixed such cases.) - With the current model it's easy to call `super_fold_with` within `TypeFolder` impls where `fold_with` should be called. The new approach makes this mistake impossible, and this commit fixes a number of such cases. - It's potentially faster, because it avoids the `fold_with` -> `super_fold_with` call in all cases except types of interest. A lot of the time the compile would inline those away, but not necessarily always.		2022-06-08 09:24:03 +10:00
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src	Folding revamp.	2022-06-08 09:24:03 +10:00
Cargo.toml	Initial fixes on top of type interner commit	2022-05-28 11:38:22 -07:00