rust/compiler/rustc_monomorphize/src
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
..
partitioning rustc: Panic by default in DefIdTree::parent 2022-05-02 01:56:50 +03:00
collector.rs call instantiation_mode when pushing a new mono_item 2022-05-26 09:36:54 +08:00
lib.rs Remove crate visibility usage in compiler 2022-05-20 20:04:54 -04:00
polymorphize.rs Folding revamp. 2022-06-08 09:24:03 +10:00
util.rs Remove crate visibility usage in compiler 2022-05-20 20:04:54 -04:00