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rustdoc: heavily simplify the synthesis of auto trait impls `gd --numstat HEAD~2 HEAD src/librustdoc/clean/auto_trait.rs` **+315 -705** 🟩🟥🟥🟥⬛ --- As outlined in issue #113015, there are currently 3[^1] large separate routines that “clean” `rustc_middle::ty` data types related to generics & predicates to rustdoc data types. Every single one has their own kinds of bugs. While I've patched a lot of bugs in each of the routines in the past, it's about time to unify them. This PR is only the first in a series. It completely **yanks** the custom “bounds cleaning” of mod `auto_trait` and reuses the routines found in mod `simplify`. As alluded to, `simplify` is also flawed but it's still more complete than `auto_trait`'s routines. [See also my review comment over at `tests/rustdoc/synthetic_auto/bounds.rs`](https://github.com/rust-lang/rust/pull/123340#discussion_r1546900539). This is preparatory work for rewriting “bounds cleaning” from scratch in follow-up PRs in order to finally [fix] #113015. Apart from that, I've eliminated all potential sources of *instability* in the rendered output. See also #119597. I'm pretty sure this fixes #119597. This PR does not attempt to fix [any other issues related to synthetic auto trait impls](https://github.com/rust-lang/rust/issues?q=is%3Aissue+is%3Aopen+label%3AA-synthetic-impls%20label%3AA-auto-traits). However, it's definitely meant to be a *stepping stone* by making `auto_trait` more contributor-friendly. --- * Replace `FxHash{Map,Set}` with `FxIndex{Map,Set}` to guarantee a stable iteration order * Or as a perf opt, `UnordSet` (a thin wrapper around `FxHashSet`) in cases where we never iterate over the set. * Yes, we do make use of `swap_remove` but that shouldn't matter since all the callers are deterministic. It does make the output less “predictable” but it's still better than before. Ofc, I rely on `rustc_infer` being deterministic. I hope that holds. * Utilizing `clean::simplify` over the custom “bounds cleaning” routines wipes out the last reference to `collect_referenced_late_bound_regions` in rustdoc (`simplify` uses `bound_vars`) which was a source of instability / unpredictability (cc #116388) * Remove the types `RegionTarget` and `RegionDeps` from `librustdoc`. They were duplicates of the identical types found in `rustc`. Just import them from `rustc`. For some reason, they were duplicated when splitting `auto_trait` in two in #49711. * Get rid of the useless “type namespace” `AutoTraitFinder` in `librustdoc` * The struct only held a `DocContext`, it was over-engineered * Turn the associated functions into free ones * Eliminates rightward drift; increases legibility * `rustc` also contains a useless `AutoTraitFinder` struct but I plan on removing that in a follow-up PR * Rename a bunch of methods to be way more descriptive * Eliminate `use super::*;` * Lead to `clean/mod.rs` accumulating a lot of unnecessary imports * Made `auto_traits` less modular * Eliminate a custom `TypeFolder`: We can just use the rustc helper `fold_regions` which does that for us I plan on adding extensive documentation to `librustdoc`'s `auto_trait` in follow-up PRs. I don't want to do that in this PR because further refactoring & bug fix PRs may alter the overall structure of `librustdoc`'s & `rustc`'s `auto_trait` modules to a great degree. I'm slowly digging into the dark details of `rustc`'s `auto_trait` module again and once I have the full picture I will be able to provide proper docs. --- While this PR does indeed touch `rustc`'s `auto_trait` — mostly tiny refactorings — I argue this PR doesn't need any compiler reviewers next to rustdoc ones since that module falls under the purview of rustdoc — it used to be part of `librustdoc` after all (#49711). Sorry for not having split this into more commits. If you'd like me to I can try to split it into more atomic commits retroactively. However, I don't know if that would actually make reviewing easier. I think the best way to review this might just be to place the master version of `auto_trait` on the left of your screen and the patched one on the right, not joking. r? `@GuillaumeGomez` [^1]: Or even 4 depending on the way you're counting. |
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