Make use of `ptr::null(_mut)` instead of casting zero
There are few places that I don't replace the zero casting pointer with `ptr::null`
or `ptr::null_mut`:
```bash
% git grep -E '[ ([{]0 as \*'
src/libcore/ptr/mod.rs:216:pub const fn null<T>() -> *const T { 0 as *const T }
src/libcore/ptr/mod.rs:231:pub const fn null_mut<T>() -> *mut T { 0 as *mut T }
src/test/run-pass/consts/const-cast-ptr-int.rs:12:static a: TestStruct = TestStruct{x: 0 as *const u8};
src/test/ui/issues/issue-45730.rs:5: let x: *const _ = 0 as *const _; //~ ERROR cannot cast
src/test/ui/issues/issue-45730.rs:8: let x = 0 as *const i32 as *const _ as *mut _; //~ ERROR cannot cast
src/test/ui/issues/issue-45730.stderr:14:LL | let x: *const _ = 0 as *const _;
src/test/ui/issues/issue-45730.stderr:24:LL | let x = 0 as *const i32 as *const _ as *mut _;
src/test/ui/lint/lint-forbid-internal-unsafe.rs:15: println!("{}", evil!(*(0 as *const u8)));
src/test/ui/order-dependent-cast-inference.rs:5: let mut y = 0 as *const _;
src/test/ui/order-dependent-cast-inference.stderr:4:LL | let mut y = 0 as *const _;
```
r? @sfackler
Help LLVM better optimize slice::Iter(Mut)::len
r? @RalfJung
I've included a codegen test that fails without this change as a demonstration of usefulness.
Replace some uses of NodeId with HirId
We are still using `NodeId` in some spots where we could use `HirId` instead; this PR targets some of these spots and removes some of the associated `hir::map` functions.
test more variants of enum-int-casting
As I learned in https://github.com/rust-lang/rust/pull/61673#issuecomment-500213506, there is a code path we are not testing yet. Looks like enum-int-casting with and without an intermediate let-binding is totally different.
EDIT: The reason for this is to get rid of the cycle in definitions such as:
```rust
enum Foo {
A = 0,
B = Foo::A as isize + 2,
}
```
This has historically been supported, so a hack adding special treatment to `Enum::Variant as _` was added to keep supporting it.
weird-exprs: if if if if
The `if` keyword can be chained as long as there are enough `{...} else {...}` following, and they all return a `bool` (not required for the last one).
`if` expression can be also put inside a `match` arm guard, thus making the whole thing a little bit more confusing.
Discovered this clusterfunk while reading the reference because I have nothing better to do.
Optimize matches
Attempt to fix or improve #60571
This is breaking some diagnostics because the MIR for match arms isn't in source order any more.
cc @centril
Rollup of 6 pull requests
Successful merges:
- #61785 (note some safety concerns of raw-ptr-to-ref casts)
- #61805 (typeck: Fix ICE for blocks in repeat expr count.)
- #61813 (Remove some unnecessary symbol interner ops)
- #61824 (in which we decline to lint single-use lifetimes in `derive`d impls)
- #61844 (Change `...` to `..=` where applicable)
- #61854 (Minor cosmetic improvements to accompany PR 61825)
Failed merges:
r? @ghost
typeck: Fix ICE for blocks in repeat expr count.
Fixes#61336 (again). This PR fixes an ICE that occured when a block expression resolving to a const generic was used for the count of an array repeat expression.
r? @varkor
Limit dylib symbols
This makes `windows-gnu` match the behavior of `windows-msvc`. It probably doesn't make sense to export these symbols on other platforms either.
type_alias_enum_variants: fix#61801; allow a path pattern to infer
Fix#61801.
Given a type-relative path pattern referring to an enum variant through a type alias, allow inferring the generic argument applied in the expectation set by the scrutinee of a `match` expression.
Similar issues may exist for `let` statements but I don't know how to test for that since `PhantomData<T>` is necessary...)
The gist of the problem here was that `resolve_ty_and_res_ufcs` was called twice which is apparently no good... It is possible that this PR is papering over some deeper problem, but that is beyond my knowledge of the compiler.
r? @petrochenkov
cc @eddyb @alexreg
cc https://github.com/rust-lang/rust/pull/61682
cc https://github.com/rust-lang/rust/issues/49683
Unify all uses of 'gcx and 'tcx.
This is made possible by @Zoxc landing #57214 (see https://github.com/rust-lang/rust/pull/57214#issuecomment-465036053 for the decision).
A bit of context for the approach: just like #61722, this is *not* how I originally intended to go about this, but @Zoxc and my own experimentation independently resulted in the same conclusion:
The interim alias `type TyCx<'tcx> = TyCtxt<'tcx, 'tcx>;` attempt required more work (adding `use`s), even only for handling the `TyCtxt<'tcx, 'tcx>` case and not the general `TyCtxt<'gcx, 'tcx>` one.
What this PR is based on is the realization that `'gcx` is a special-enough name that it can be replaced, without caring for context, with `'tcx`, and then repetitions of the name `'tcx` be compacted away.
After that, only a small number of error categories remained, each category easily dealt with with either more mass replacements (e.g. `TyCtxt<'tcx, '_>` -> `TyCtxt<'tcx>`) or by hand.
For the `rustfmt` commit, I used https://github.com/rust-lang/rustfmt/issues/1324#issuecomment-482109952, and manually filtered out some noise, like in #61735 and #61722, and like the latter, there was also a weird bug to work around.
It should be reviewed separately, and dropped if unwanted (in this PR it's pretty significant).
cc @rust-lang/compiler r? @nikomatsakis
in which we decline to suggest the anonymous lifetime in declarations
The elided-lifetimes-in-path lint (part of our suite of Rust 2018 idiom lints which we are hoping to promote to Warn status) was firing with an illegal suggestion to write an anonymous lifetime in a
struct/item declaration (where we don't allow it). The linting code was already deciding whether to act on the basis of a `ParamMode` enum, indicating whether the present path-segment was part of an
expression, or anywhere else. The present case seemed to be part of the "anywhere else", and yet meriting different rules as far as the lint was concerned, so it seemed expedient to introduce a new enum member. We yank out `TyKind::Path` arm into its own method so that we can call it with our new `ParamMode` specifically when lowering struct fields—one would have hoped to think of something more elegant than this, but it definitely beats changing the signature of `lower_ty` to take a `ParamMode`!
Resolves#61124.
cc @memoryruins
r? @oli-obk
The elided-lifetimes-in-path lint (part of our suite of Rust 2018
idiom lints which we are hoping to promote to Warn status) was firing
with an illegal suggestion to write an anonymous lifetime in a
struct/item declaration (where we don't allow it). The linting code
was already deciding whether to act on the basis of a `ParamMode`
enum, indicating whether the present path-segment was part of an
expression, or anywhere else. The present case seemed to be part of
the "anywhere else", and yet meriting different rules as far as the
lint was concerned, so it seemed expedient to introduce a new enum
member. We yank out a `TyKind::Path` arm into its own method so that
we can call it with our new `ParamMode` specifically when lowering
struct fields. (The alternative strategy of changing the signature of
`lower_ty` to take a `ParamMode` would be inelegant given that most of
the `TyKind` match arm bodies therein don't concern themselves with
`ParamMode`.)
Resolves#61124.
This commit extends the work in #61698 to get the `DefId` of const
parameters from block that resolve to a const parameter (as well as
const parameters directly, as it was previously).
Allow attributes in formal function parameters
Implements https://github.com/rust-lang/rust/issues/60406.
This is my first contribution to the compiler and since this is a large and complex project, I am not fully aware of the consequences of the changes I have made.
**TODO**
- [x] Forbid some built-in attributes.
- [x] Expand cfg/cfg_attr
Generator optimization: Overlap locals that never have storage live at the same time
The specific goal of this optimization is to optimize async fns which use `await!`. Notably, `await!` has an enclosing scope around the futures it awaits ([definition](08bfe16129/src/libstd/macros.rs (L365-L381))), which we rely on to implement the optimization.
More generally, the optimization allows overlapping the storage of some locals which are never storage-live at the same time. **We care about storage-liveness when computing the layout, because knowing a field is `StorageDead` is the only way to prove it will not be accessed, either directly or through a reference.**
To determine whether we can overlap two locals in the generator layout, we look at whether they might *both* be `StorageLive` at any point in the MIR. We use the `MaybeStorageLive` dataflow analysis for this. We iterate over every location in the MIR, and build a bitset for each local of the locals it might potentially conflict with.
Next, we assign every saved local to one or more variants. The variants correspond to suspension points, and we include the set of locals live across a given suspension point in the variant. (Note that we use liveness instead of storage-liveness here; this ensures that the local has actually been initialized in each variant it has been included in. If the local is not live across a suspension point, then it doesn't need to be included in that variant.). It's important to note that the variants are a "view" into our layout.
For the layout computation, we use a simplified approach.
1. Start with the set of locals assigned to only one variant. The rest are disqualified.
2. For each pair of locals which may conflict *and are not assigned to the same variant*, we pick one local to disqualify from overlapping.
Disqualified locals go into a non-overlapping "prefix" at the beginning of our layout. This means they always have space reserved for them. All the locals that are allowed to overlap in each variant are then laid out after this prefix, in the "overlap zone".
So, if A and B were disqualified, and X, Y, and Z were all eligible for overlap, our generator might look something like this:
You can think of a generator as an enum, where some fields are shared between variants. e.g.
```rust
enum Generator {
Unresumed,
Poisoned,
Returned,
Suspend0(A, B, X),
Suspend1(B),
Suspend2(A, Y, Z),
}
```
where every mention of `A` and `B` refer to the same field, which does not move when changing variants. Note that `A` and `B` would automatically be sent to the prefix in this example. Assuming that `X` is never `StorageLive` at the same time as either `Y` or `Z`, it would be allowed to overlap with them.
Note that if two locals (`Y` and `Z` in this case) are assigned to the same variant in our generator, their memory would never overlap in the layout. Thus they can both be eligible for the overlapping section, even if they are storage-live at the same time.
---
Depends on:
- [x] #59897 Multi-variant layouts for generators
- [x] #60840 Preserve local scopes in generator MIR
- [x] #61373 Emit StorageDead along unwind paths for generators
Before merging:
- [x] ~Wrap the types of all generator fields in `MaybeUninitialized` in layout::ty::field~ (opened #60889)
- [x] Make PR description more complete (e.g. explain why storage liveness is important and why we have to check every location)
- [x] Clean up TODO
- [x] Fix the layout code to enforce that the same field never moves around in the generator
- [x] Add tests for async/await
- [x] ~Reduce # bits we store by half, since the conflict relation is symmetric~ (note: decided not to do this, for simplicity)
- [x] Store liveness information for each yield point in our `GeneratorLayout`, that way we can emit more useful debuginfo AND tell miri which fields are definitely initialized for a given variant (see discussion at https://github.com/rust-lang/rust/pull/59897#issuecomment-489468627)
Remove some legacy proc macro flavors
Namely
- `IdentTT` (`foo! ident { ... }`). Can be replaced with `foo! { ident ... }` or something similar.
- `MultiDecorator`. Can be replaced by `MultiModifier` (aka `LegacyAttr` after renaming).
- `DeclMacro`. It was a less powerful duplicate of `NormalTT` (aka `LegacyBang` after renaming) and can be replaced by it.
Stuff like this slows down any attempts to refactor the expansion infra, so it's desirable to retire it already.
I'm not sure whether a lang team decision is necessary, but would be nice to land this sooner because I have some further work in this area scheduled.
The documentation commit (a9397fd0d5) describes how the remaining variants are different from each other and shows that there's actually some system behind them.
The last commit renames variants of `SyntaxExtension` in more systematic way.
- `ProcMacro` -> `Bang`
- `NormalTT` -> `LegacyBang`
- `AttrProcMacro` -> `Attr`
- `MultiModifier` -> `LegacyAttr`
- `ProcMacroDerive` -> `Derive`
- `BuiltinDerive` -> `LegacyDerive`
All the `Legacy*` variants are AST-based, as opposed to "modern" token-based variants.
