Improve `unused_unsafe` lint
I’m going to add some motivation and explanation below, particularly pointing the changes in behavior from this PR.
_Edit:_ Looking for existing issues, looks like this PR fixes#88260.
_Edit2:_ Now also contains code that closes#90776.
Main motivation: Fixes some issues with the current behavior. This PR is
more-or-less completely re-implementing the unused_unsafe lint; it’s also only
done in the MIR-version of the lint, the set of tests for the `-Zthir-unsafeck`
version no longer succeeds (and is thus disabled, see `lint-unused-unsafe.rs`).
On current nightly,
```rs
unsafe fn unsf() {}
fn inner_ignored() {
unsafe {
#[allow(unused_unsafe)]
unsafe {
unsf()
}
}
}
```
doesn’t create any warnings. This situation is not unrealistic to come by, the
inner `unsafe` block could e.g. come from a macro. Actually, this PR even
includes removal of one unused `unsafe` in the standard library that was missed
in a similar situation. (The inner `unsafe` coming from an external macro hides
the warning, too.)
The reason behind this problem is how the check currently works:
* While generating MIR, it already skips nested unsafe blocks (i.e. unsafe
nested in other unsafe) so that the inner one is always the one considered
unused
* To differentiate the cases of no unsafe operations inside the `unsafe` vs.
a surrounding `unsafe` block, there’s some ad-hoc magic walking up the HIR to
look for surrounding used `unsafe` blocks.
There’s a lot of problems with this approach besides the one presented above.
E.g. the MIR-building uses checks for `unsafe_op_in_unsafe_fn` lint to decide
early whether or not `unsafe` blocks in an `unsafe fn` are redundant and ought
to be removed.
```rs
unsafe fn granular_disallow_op_in_unsafe_fn() {
unsafe {
#[deny(unsafe_op_in_unsafe_fn)]
{
unsf();
}
}
}
```
```
error: call to unsafe function is unsafe and requires unsafe block (error E0133)
--> src/main.rs:13:13
|
13 | unsf();
| ^^^^^^ call to unsafe function
|
note: the lint level is defined here
--> src/main.rs:11:16
|
11 | #[deny(unsafe_op_in_unsafe_fn)]
| ^^^^^^^^^^^^^^^^^^^^^^
= note: consult the function's documentation for information on how to avoid undefined behavior
warning: unnecessary `unsafe` block
--> src/main.rs:10:5
|
9 | unsafe fn granular_disallow_op_in_unsafe_fn() {
| --------------------------------------------- because it's nested under this `unsafe` fn
10 | unsafe {
| ^^^^^^ unnecessary `unsafe` block
|
= note: `#[warn(unused_unsafe)]` on by default
```
Here, the intermediate `unsafe` was ignored, even though it contains a unsafe
operation that is not allowed to happen in an `unsafe fn` without an additional `unsafe` block.
Also closures were problematic and the workaround/algorithms used on current
nightly didn’t work properly. (I skipped trying to fully understand what it was
supposed to do, because this PR uses a completely different approach.)
```rs
fn nested() {
unsafe {
unsafe { unsf() }
}
}
```
```
warning: unnecessary `unsafe` block
--> src/main.rs:10:9
|
9 | unsafe {
| ------ because it's nested under this `unsafe` block
10 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
|
= note: `#[warn(unused_unsafe)]` on by default
```
vs
```rs
fn nested() {
let _ = || unsafe {
let _ = || unsafe { unsf() };
};
}
```
```
warning: unnecessary `unsafe` block
--> src/main.rs:9:16
|
9 | let _ = || unsafe {
| ^^^^^^ unnecessary `unsafe` block
|
= note: `#[warn(unused_unsafe)]` on by default
warning: unnecessary `unsafe` block
--> src/main.rs:10:20
|
10 | let _ = || unsafe { unsf() };
| ^^^^^^ unnecessary `unsafe` block
```
*note that this warning kind-of suggests that **both** unsafe blocks are redundant*
--------------------------------------------------------------------------------
I also dislike the fact that it always suggests keeping the outermost `unsafe`.
E.g. for
```rs
fn granularity() {
unsafe {
unsafe { unsf() }
unsafe { unsf() }
unsafe { unsf() }
}
}
```
I prefer if `rustc` suggests removing the more-course outer-level `unsafe`
instead of the fine-grained inner `unsafe` blocks, which it currently does on nightly:
```
warning: unnecessary `unsafe` block
--> src/main.rs:10:9
|
9 | unsafe {
| ------ because it's nested under this `unsafe` block
10 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
|
= note: `#[warn(unused_unsafe)]` on by default
warning: unnecessary `unsafe` block
--> src/main.rs:11:9
|
9 | unsafe {
| ------ because it's nested under this `unsafe` block
10 | unsafe { unsf() }
11 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
warning: unnecessary `unsafe` block
--> src/main.rs:12:9
|
9 | unsafe {
| ------ because it's nested under this `unsafe` block
...
12 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
```
--------------------------------------------------------------------------------
Needless to say, this PR addresses all these points. For context, as far as my
understanding goes, the main advantage of skipping inner unsafe blocks was that
a test case like
```rs
fn top_level_used() {
unsafe {
unsf();
unsafe { unsf() }
unsafe { unsf() }
unsafe { unsf() }
}
}
```
should generate some warning because there’s redundant nested `unsafe`, however
every single `unsafe` block _does_ contain some statement that uses it. Of course
this PR doesn’t aim change the warnings on this kind of code example, because
the current behavior, warning on all the inner `unsafe` blocks, makes sense in this case.
As mentioned, during MIR building all the unsafe blocks *are* kept now, and usage
is attributed to them. The way to still generate a warning like
```
warning: unnecessary `unsafe` block
--> src/main.rs:11:9
|
9 | unsafe {
| ------ because it's nested under this `unsafe` block
10 | unsf();
11 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
|
= note: `#[warn(unused_unsafe)]` on by default
warning: unnecessary `unsafe` block
--> src/main.rs:12:9
|
9 | unsafe {
| ------ because it's nested under this `unsafe` block
...
12 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
warning: unnecessary `unsafe` block
--> src/main.rs:13:9
|
9 | unsafe {
| ------ because it's nested under this `unsafe` block
...
13 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
```
in this case is by emitting a `unused_unsafe` warning for all of the `unsafe`
blocks that are _within a **used** unsafe block_.
The previous code had a little HIR traversal already anyways to collect a set of
all the unsafe blocks (in order to afterwards determine which ones are unused
afterwards). This PR uses such a traversal to do additional things including logic
like _always_ warn for an `unsafe` block that’s inside of another **used**
unsafe block. The traversal is expanded to include nested closures in the same go,
this simplifies a lot of things.
The whole logic around `unsafe_op_in_unsafe_fn` is a little complicated, there’s
some test cases of corner-cases in this PR. (The implementation involves
differentiating between whether a used unsafe block was used exclusively by
operations where `allow(unsafe_op_in_unsafe_fn)` was active.) The main goal was
to make sure that code should compile successfully if all the `unused_unsafe`-warnings
are addressed _simultaneously_ (by removing the respective `unsafe` blocks)
no matter how complicated the patterns of `unsafe_op_in_unsafe_fn` being
disallowed and allowed throughout the function are.
--------------------------------------------------------------------------------
One noteworthy design decision I took here: An `unsafe` block
with `allow(unused_unsafe)` **is considered used** for the purposes of
linting about redundant contained unsafe blocks. So while
```rs
fn granularity() {
unsafe { //~ ERROR: unnecessary `unsafe` block
unsafe { unsf() }
unsafe { unsf() }
unsafe { unsf() }
}
}
```
warns for the outer `unsafe` block,
```rs
fn top_level_ignored() {
#[allow(unused_unsafe)]
unsafe {
#[deny(unused_unsafe)]
{
unsafe { unsf() } //~ ERROR: unnecessary `unsafe` block
unsafe { unsf() } //~ ERROR: unnecessary `unsafe` block
unsafe { unsf() } //~ ERROR: unnecessary `unsafe` block
}
}
}
```
warns on the inner ones.
Move ty::print methods to Drop-based scope guards
Primary goal is reducing codegen of the TLS access for each closure, which shaves ~3 seconds of bootstrap time over rustc as a whole.
Specifically, rename the `Const` struct as `ConstS` and re-introduce `Const` as
this:
```
pub struct Const<'tcx>(&'tcx Interned<ConstS>);
```
This now matches `Ty` and `Predicate` more closely, including using
pointer-based `eq` and `hash`.
Notable changes:
- `mk_const` now takes a `ConstS`.
- `Const` was copy, despite being 48 bytes. Now `ConstS` is not, so need a
we need separate arena for it, because we can't use the `Dropless` one any
more.
- Many `&'tcx Const<'tcx>`/`&Const<'tcx>` to `Const<'tcx>` changes
- Many `ct.ty` to `ct.ty()` and `ct.val` to `ct.val()` changes.
- Lots of tedious sigil fiddling.
Specifically, change `Region` from this:
```
pub type Region<'tcx> = &'tcx RegionKind;
```
to this:
```
pub struct Region<'tcx>(&'tcx Interned<RegionKind>);
```
This now matches `Ty` and `Predicate` more closely.
Things to note
- Regions have always been interned, but we haven't been using pointer-based
`Eq` and `Hash`. This is now happening.
- I chose to impl `Deref` for `Region` because it makes pattern matching a lot
nicer, and `Region` can be viewed as just a smart wrapper for `RegionKind`.
- Various methods are moved from `RegionKind` to `Region`.
- There is a lot of tedious sigil changes.
- A couple of types like `HighlightBuilder`, `RegionHighlightMode` now have a
`'tcx` lifetime because they hold a `Ty<'tcx>`, so they can call `mk_region`.
- A couple of test outputs change slightly, I'm not sure why, but the new
outputs are a little better.
Specifically, change `Ty` from this:
```
pub type Ty<'tcx> = &'tcx TyS<'tcx>;
```
to this
```
pub struct Ty<'tcx>(Interned<'tcx, TyS<'tcx>>);
```
There are two benefits to this.
- It's now a first class type, so we can define methods on it. This
means we can move a lot of methods away from `TyS`, leaving `TyS` as a
barely-used type, which is appropriate given that it's not meant to
be used directly.
- The uniqueness requirement is now explicit, via the `Interned` type.
E.g. the pointer-based `Eq` and `Hash` comes from `Interned`, rather
than via `TyS`, which wasn't obvious at all.
Much of this commit is boring churn. The interesting changes are in
these files:
- compiler/rustc_middle/src/arena.rs
- compiler/rustc_middle/src/mir/visit.rs
- compiler/rustc_middle/src/ty/context.rs
- compiler/rustc_middle/src/ty/mod.rs
Specifically:
- Most mentions of `TyS` are removed. It's very much a dumb struct now;
`Ty` has all the smarts.
- `TyS` now has `crate` visibility instead of `pub`.
- `TyS::make_for_test` is removed in favour of the static `BOOL_TY`,
which just works better with the new structure.
- The `Eq`/`Ord`/`Hash` impls are removed from `TyS`. `Interned`s impls
of `Eq`/`Hash` now suffice. `Ord` is now partly on `Interned`
(pointer-based, for the `Equal` case) and partly on `TyS`
(contents-based, for the other cases).
- There are many tedious sigil adjustments, i.e. adding or removing `*`
or `&`. They seem to be unavoidable.
Lazy type-alias-impl-trait
Previously opaque types were processed by
1. replacing all mentions of them with inference variables
2. memorizing these inference variables in a side-table
3. at the end of typeck, resolve the inference variables in the side table and use the resolved type as the hidden type of the opaque type
This worked okayish for `impl Trait` in return position, but required lots of roundabout type inference hacks and processing.
This PR instead stops this process of replacing opaque types with inference variables, and just keeps the opaque types around.
Whenever an opaque type `O` is compared with another type `T`, we make the comparison succeed and record `T` as the hidden type. If `O` is compared to `U` while there is a recorded hidden type for it, we grab the recorded type (`T`) and compare that against `U`. This makes implementing
* https://github.com/rust-lang/rfcs/pull/2515
much simpler (previous attempts on the inference based scheme were very prone to ICEs and general misbehaviour that was not explainable except by random implementation defined oddities).
r? `@nikomatsakis`
fixes#93411fixes#88236
by using an opaque type obligation to bubble up comparisons between opaque types and other types
Also uses proper obligation causes so that the body id works, because out of some reason nll uses body ids for logic instead of just diagnostics.
The unconditional recursion lint determines if all execution paths
eventually lead to a self-recursive call.
The implementation always follows unwinding edges which limits its
practical utility. For example, it would not lint function `f` because a
call to `g` might unwind. It also wouldn't lint function `h` because an
overflow check preceding the self-recursive call might unwind:
```rust
pub fn f() {
g();
f();
}
pub fn g() { /* ... */ }
pub fn h(a: usize) {
h(a + 1);
}
```
To avoid the issue, assume that terminators that might continue
execution along non-unwinding edges do so.
Replace `NestedVisitorMap` with generic `NestedFilter`
This is an attempt to make the `intravisit::Visitor` API simpler and "more const" with regard to nested visiting.
With this change, `intravisit::Visitor` does not visit nested things by default, unless you specify `type NestedFilter = nested_filter::OnlyBodies` (or `All`). `nested_visit_map` returns `Self::Map` instead of `NestedVisitorMap<Self::Map>`. It panics by default (unreachable if `type NestedFilter` is omitted).
One somewhat trixty thing here is that `nested_filter::{OnlyBodies, All}` live in `rustc_middle` so that they may have `type Map = map::Map` and so that `impl Visitor`s never need to specify `type Map` - it has a default of `Self::NestedFilter::Map`.
Remove deprecated LLVM-style inline assembly
The `llvm_asm!` was deprecated back in #87590 1.56.0, with intention to remove
it once `asm!` was stabilized, which already happened in #91728 1.59.0. Now it
is time to remove `llvm_asm!` to avoid continued maintenance cost.
Closes#70173.
Closes#92794.
Closes#87612.
Closes#82065.
cc `@rust-lang/wg-inline-asm`
r? `@Amanieu`
Closure capture cleanup & refactor
Follow up of #89648
Each commit is self-contained and the rationale/changes are documented in the commit message, so it's advisable to review commit by commit.
The code is significantly cleaner (at least IMO), but that could have some perf implication, so I'd suggest a perf run.
r? `@wesleywiser`
cc `@arora-aman`
The field is also renamed from `ident` to `name. In most cases,
we don't actually need the `Span`. A new `ident` method is added
to `VariantDef` and `FieldDef`, which constructs the full `Ident`
using `tcx.def_ident_span()`. This method is used in the cases
where we actually need an `Ident`.
This makes incremental compilation properly track changes
to the `Span`, without all of the invalidations caused by storing
a `Span` directly via an `Ident`.
Region info is completely unnecessary for upvar capture kind computation
and is only needed to create the final upvar tuple ty. Doing so makes
creation of UpvarCapture very cheap and expose further cleanup opportunity.
The `AggregateKind` enum ends up in the final mir `Body`. Currently,
any changes to `AdtDef` (regardless of how significant they are)
will legitimately cause the overall result of `optimized_mir` to change,
invalidating any codegen re-use involving that mir.
This will get worse once we start hashing the `Span` inside `FieldDef`
(which is itself contained in `AdtDef`).
To try to reduce these kinds of invalidations, this commit changes
`AggregateKind::Adt` to store just the `DefId`, instead of the full
`AdtDef`. This allows the result of `optimized_mir` to be unchanged
if the `AdtDef` changes in a way that doesn't actually affect any
of the MIR we build.
Implement let-else type annotations natively
Tracking issue: #87335Fixes#89688, fixes#89807, edit: fixes #89960 as well
As explained in https://github.com/rust-lang/rust/issues/89688#issuecomment-940405082, the previous desugaring moved the let-else scrutinee into a dummy variable, which meant if you wanted to refer to it again in the else block, it had moved.
This introduces a new hir type, ~~`hir::LetExpr`~~ `hir::Let`, which takes over all the fields of `hir::ExprKind::Let(...)` and adds an optional type annotation. The `hir::Let` is then treated like a `hir::Local` when type checking a function body, specifically:
* `GatherLocalsVisitor` overrides a new `Visitor::visit_let_expr` and does pretty much exactly what it does for `visit_local`, assigning a local type to the `hir::Let` ~~(they could be deduplicated but they are right next to each other, so at least we know they're the same)~~
* It reuses the code in `check_decl_local` to typecheck the `hir::Let`, simply returning 'bool' for the expression type after doing that.
* ~~`FnCtxt::check_expr_let` passes this local type in to `demand_scrutinee_type`, and then imitates check_decl_local's pattern checking~~
* ~~`demand_scrutinee_type` (the blindest change for me, please give this extra scrutiny) uses this local type instead of of creating a new one~~
* ~~Just realised the `check_expr_with_needs` was passing NoExpectation further down, need to pass the type there too. And apparently this Expectation API already exists.~~
Some other misc notes:
* ~~Is the clippy code supposed to be autoformatted? I tried not to give huge diffs but maybe some rustfmt changes simply haven't hit it yet.~~
* in `rustc_ast_lowering/src/block.rs`, I noticed some existing `self.alias_attrs()` calls in `LoweringContext::lower_stmts` seem to be copying attributes from the lowered locals/etc to the statements. Is that right? I'm new at this, I don't know.
