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| author | bors <bors@rust-lang.org> | 2023-04-19 17:01:06 +0000 |
|---|---|---|
| committer | bors <bors@rust-lang.org> | 2023-04-19 17:01:06 +0000 |
| commit | df0d9b492da81a647eedf17210cf55b86a44888c (patch) | |
| tree | 34bd07a1e2076879a4dee6c01856236e47e7c60d /tests/rustdoc-js-std/parser-errors.js | |
| parent | 3a5c8e91f094bb1cb1346651fe3512f0b603d826 (diff) | |
| parent | 10ec03c3fb4509f96df3aa8264858b76e81c9aa1 (diff) | |
| download | rust-df0d9b492da81a647eedf17210cf55b86a44888c.tar.gz | |
Auto merge of #110496 - WaffleLapkin:🏳️⚧️sound, r=compiler-errors
Don't transmute `&List<GenericArg>` <-> `&List<Ty>`
In #93505 we allowed safely transmuting between `&List<GenericArg<'_>>` and `&List<Ty<'_>>`. This was possible because `GenericArg` is a tagged pointer and the tag for types is `0b00`, such that a `GenericArg` with a type inside has the same layout as `Ty`.
While this was meant as an optimization, it doesn't look like it was actually any perf or max-rss win (see https://github.com/rust-lang/rust/pull/94799#issuecomment-1064340003, https://github.com/rust-lang/rust/pull/94841, https://github.com/rust-lang/rust/pull/110496#issuecomment-1513799140).
Additionally the way it was done is quite fragile — `unsafe` code was not properly documented or contained in a module, types were not marked as `repr(C)` (making the transmutes possibly unsound). All of this makes the code maintenance harder and blocks other possible optimizations (as an example I've found out about these `transmutes` when my change caused them to sigsegv compiler).
Thus, I think we can safely (pun intended) remove those transmutes, making maintenance easier, optimizations possible, code less cursed, etc.
r? `@compiler-errors`
Diffstat (limited to 'tests/rustdoc-js-std/parser-errors.js')
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