We add union fields access (in both expressions and patterns) and inline assembly.
That completes the unsafe check (there are some other unsafe things but they are unstable), and so also opens the door to reporting unused unsafe without annoying people about their not-unused unsafe blocks.
Thanks to the observation (supported by counting) that the vast majority paths have neither generics no type anchors, and thanks to a new datastructure `ThinVecWithHeader` that is essentially `(T, Box<[U]>)` but with the size of a single pointer, we are able to reach this feat.
This (together with `ThinVecWithHeader`) makes the possibility to shrink `TypeRef`, because most types are paths.
So that given a `TypeRef` we will be able to trace it back to source code.
This is necessary to be able to provide diagnostics for lowering to chalk tys, since the input to that is `TypeRef`.
This means that `TypeRef`s now have an identity, which means storing them in arena and not interning them, which is an unfortunate (but necessary) loss but also a pretty massive change. Luckily, because of the separation layer we have for IDE and HIR, this change never crosses the IDE boundary.
E.g.:
```rust
let v;
macro_rules! m { () => { v }; }
```
This was an existing bug, but it was less severe because unless the variable was shadowed it would be correctly resolved. With hygiene however, without this fix the variable is never resolved.
Or macro_rules hygiene, or mixed site hygiene. In other words, hygiene for variables and labels but not items.
The realization that made me implement this was that while "full" hygiene (aka. def site hygiene) is really hard for us to implement, and will likely involve intrusive changes and performance losses, since every `Name` will have to carry hygiene, mixed site hygiene is very local: it applies only to bodies, and we very well can save it in a side map with minor losses.
This fixes one diagnostic in r-a that was about `izip!()` using hygiene (yay!) but it introduces a huge number of others, because of #18262. Up until now this issue wasn't a major problem because it only affected few cases, but with hygiene identifiers referred by macros like that are not resolved at all. The next commit will fix that.
And few more fixups.
I was worried this will lead to more memory usage since `ExprOrPatId` is double the size of `ExprId`, but this does not regress `analysis-stats .`. If this turns out to be a problem, we can easily use the high bit to encode this information.
Instead of lowering them to `<expr> = <expr>`, then hacking on-demand to resolve them, we lower them to `<pat> = <expr>`, and use the pattern infrastructure to handle them. It turns out, destructuring assignments are surprisingly similar to pattern bindings, and so only minor modifications are needed.
This fixes few bugs that arose because of the non-uniform handling (for example, MIR lowering not handling slice and record patterns, and closure capture calculation not handling destructuring assignments at all), and furthermore, guarantees we won't have such bugs in the future, since the programmer will always have to explicitly handle `Expr::Assignment`.
Tests don't pass yet; that's because the generated patterns do not exist in the source map. The next commit will fix that.
compiler: Adopt rust-analyzer impls for `LayoutCalculatorError`
We're about to massively churn the internals of `rustc_abi`. To minimize the immediate and future impact on rust-analyzer, as a subtree that depends on this crate, grow some API on `LayoutCalculatorError` that reflects their uses of it. This way we can nest the type in theirs, and they can just call functions on it without having to inspect and flatten-out its innards.
fix: Do not consider mutable usage of deref to `*mut T` as deref_mut
Fixes#15799
We are doing some heuristics for deciding whether the given deref is deref or deref_mut here;
5982d9c420/crates/hir-ty/src/infer/mutability.rs (L182-L200)
But this heuristic is erroneous if we are dereferencing to a mut ptr and normally those cases are filtered out here as builtin;
5982d9c420/crates/hir-ty/src/mir/lower/as_place.rs (L165-L177)
Howerver, this works not so well if the given dereferencing is double dereferencings like the case in the #15799.
```rust
struct WrapPtr(*mut u32);
impl core::ops::Deref for WrapPtr {
type Target = *mut u32;
fn deref(&self) -> &Self::Target {
&self.0
}
}
fn main() {
let mut x = 0u32;
let wrap = WrapPtr(&mut x);
unsafe {
**wrap = 6;
}
}
```
Here are two - outer and inner - dereferences here, and the outer dereference is marked as deref_mut because there is an assignment operation.
And this deref_mut marking is propagated into the inner dereferencing.
In the later MIR lowering, the outer dereference is filtered out as it's expr type is `*mut u32`, but the expr type in the inner dereference is an ADT, so this false-mutablility is not filtered out.
This PR cuts propagation of this false mutablilty chain if the expr type is mut ptr.
Since this happens before the resolve_all, it may have some limitations when the expr type is determined as mut ptr at the very end of inferencing, but I couldn't find simple fix for it 🤔
before, when formatting struct constructor for `struct S(usize, usize)` it would format as:
extern "rust-call" S(usize, usize) -> S
but after this change, we'll format as:
fn S(usize, usize) -> S
