This change makes it easier to follow the control flow.
I also moved the end-of-line comments attached to some symbols to before
the symbol listing. This allows rustfmt to format the code; otherwise no
formatting occurs (see rust-lang/rustfmt#4750).
Fixes issue #82920
Even if an item does not change between compilation sessions, it may end
up with a different `DefId`, since inserting/deleting an item affects
the `DefId`s of all subsequent items. Therefore, we use a `DefPathHash`
in the incremental compilation system, which is stable in the face of
changes to unrelated items.
In particular, the query system will consider the inputs to a query to
be unchanged if any `DefId`s in the inputs have their `DefPathHash`es
unchanged. Queries are pure functions, so the query result should be
unchanged if the query inputs are unchanged.
Unfortunately, it's possible to inadvertantly make a query result
incorrectly change across compilations, by relying on the specific value
of a `DefId`. Specifically, if the query result is a slice that gets
sorted by `DefId`, the precise order will depend on how the `DefId`s got
assigned in a particular compilation session. If some definitions end up
with different `DefId`s (but the same `DefPathHash`es) in a subsequent
compilation session, we will end up re-computing a *different* value for
the query, even though the query system expects the result to unchanged
due to the unchanged inputs.
It turns out that we have been sorting the predicates computed during
`astconv` by their `DefId`. These predicates make their way into the
`super_predicates_that_define_assoc_type`, which ends up getting used to
compute the vtables of trait objects. This, re-ordering these predicates
between compilation sessions can lead to undefined behavior at runtime -
the query system will re-use code built with a *differently ordered*
vtable, resulting in the wrong method being invoked at runtime.
This PR avoids sorting by `DefId` in `astconv`, fixing the
miscompilation. However, it's possible that other instances of this
issue exist - they could also be easily introduced in the future.
To fully fix this issue, we should
1. Turn on `-Z incremental-verify-ich` by default. This will cause the
compiler to ICE whenver an 'unchanged' query result changes between
compilation sessions, instead of causing a miscompilation.
2. Remove the `Ord` impls for `CrateNum` and `DefId`. This will make it
difficult to introduce ICEs in the first place.
Issue #82920 showed that the kind of bugs caught by this flag have
soundness implications.
This causes performance regressions of up to 15.2% during incremental
compilation, but this is necessary to catch miscompilations caused by
bugs in query implementations.
rustc_query_system: simplify QueryCache::iter
Minor cleanup to reduce a small amount of complexity and code bloat.
Reduces the number of mono items in rustc_query_impl by 15%.
2229: Handle capturing a reference into a repr packed struct
RFC 1240 states that it is unsafe to capture references into a
packed-struct. This PR ensures that when a closure captures a precise
path, we aren't violating this safety constraint.
To acheive so we restrict the capture precision to the struct itself.
An interesting edge case where we decided to restrict precision:
```rust
struct Foo(String);
let foo: Foo;
let c = || {
println!("{}", foo.0);
let x = foo.0;
}
```
Given how closures get desugared today, foo.0 will be moved into the
closure, making the `println!`, safe. However this can be very subtle
and also will be unsafe if the closure gets inline.
Closes: https://github.com/rust-lang/project-rfc-2229/issues/33
r? `@nikomatsakis`
Basically, it doesn't make sense to generate those things every time
you search. That generates a bunch of stuff for the GC to clean up,
when, if the user wanted to do another search, it would just need
to re-do it again.
Every time splice() is called, another temporary object is created.
This version, which uses plain objects as a sort of Hash Bag,
should only produce one temporary object each time it's called.
There is no reason for this function to return an object,
since it is always used for getting at the name anyhow.
It's used in the inner loop for some popular functions,
so we want to avoid allocating in it.
Allow calling *const methods on *mut values
This allows `*const` methods to be called on `*mut` values.
TODOs:
- [x] ~~Remove debug logs~~ Done.
- [x] ~~I haven't tested, but I think this currently won't work when the `self` value has type like `&&&&& *mut X` because I don't do any autoderefs when probing. To fix this the new code in `rustc_typeck::check::method::probe` needs to reuse `pick_method` somehow as I think that's the function that autoderefs.~~ This works, because autoderefs are done before calling `pick_core`, in `method_autoderef_steps`, called by `probe_op`.
- [x] ~~I should probably move the new `Pick` to `pick_autorefd_method`. If not, I should move it to its own function.~~ Done.
- [ ] ~~Test this with a `Pick` with `to_ptr = true` and `unsize = true`.~~ I think this case cannot happen, because we don't have any array methods with `*mut [X]` receiver. I should confirm that this is true and document this. I've placed two assertions about this.
- [x] ~~Maybe give `(Mutability, bool)` a name and fields~~ I now have a `to_const_ptr` field in `Pick`.
- [x] ~~Changes in `adjust_self_ty` is quite hacky. The problem is we can't deref a pointer, and even if we don't have an adjustment to get the address of a value, so to go from `*mut` to `*const` we need a special case.~~ There's still a special case for `to_const_ptr`, but I'm not sure if we can avoid this.
- [ ] Figure out how `reached_raw_pointer` stuff is used. I suspect only for error messages.
Fixes#80258
Allow configuring `rustdoc --disable-minification` in config.toml
This way, you can debug rustdoc's JavaScript and CSS file with normal F12 Dev Tools and you'll have useful line numbers to work with.
Don't implement mem::replace with mem::swap.
`swap` is a complicated operation, so this changes the implementation of `replace` to use `read` and `write` instead.
See https://github.com/rust-lang/rust/pull/83019.
I wrote there:
> Implementing the simpler operation (replace) with the much more complicated operation (swap) doesn't make a whole lot of sense. `replace` is just read+write, and the primitive for moving out of a `&mut`. `swap` is for doing that to *two* `&mut` at the same time, which is both more niche and more complicated (as shown by `swap_nonoverlapping_bytes`).
This could be especially interesting for `Option<VeryLargeStruct>::take()`, since swapping such a large structure with `swap_nonoverlapping_bytes` is going to be much less efficient than `ptr::write()`'ing a `None`.
But also for small values where `swap` just reads/writes using temporary variable, this makes a `replace` or `take` operation simpler:
