Handle desugaring in impl trait bound suggestion
Fixes#79843.
When an associated type of a generic function parameter needs extra bounds, the diagnostics may suggest replacing an `impl Trait` with a named type parameter so that it can be referenced in the where clause. On stable and nightly, the suggestion can be malformed, for instance transforming:
```rust
async fn run(_: &(), foo: impl Foo) -> std::io::Result<()>
```
Into:
```rust
async fn run(_: &, F: Foo(), foo: F) -> std::io::Result<()> where <F as Foo>::Bar: Send
^^^^^^^^ ^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
Where we want something like:
```rust
async fn run<F: Foo>(_: &(), foo: F) -> std::io::Result<()> where <F as Foo>::Bar: Send
^^^^^^^^ ^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
The problem is that the elided lifetime of `&()` is added as a generic parameter when desugaring the async fn; the suggestion code sees this as an existing generic parameter and tries to use its span as an anchor to inject `F` into the parameter list. There doesn't seem to be an entirely principled way to check which generic parameters in the HIR were explicitly named in the source, so this commit changes the heuristics when generating the suggestion to only consider type parameters whose spans are contained within the span of the `Generics` when determining how to insert an additional type parameter into the declaration. (And to be safe it also excludes parameters whose spans are marked as originating from desugaring, although that doesn't seem to handle this elided lifetime.)
Turn quadratic time on number of impl blocks into linear time
Previously, if you had a lot of inherent impl blocks on a type like:
```Rust
struct Foo;
impl Foo { fn foo_1() {} }
// ...
impl Foo { fn foo_100_000() {} }
```
The compiler would be very slow at processing it, because
an internal algorithm would run in O(n^2), where n is the number
of impl blocks. Now, we add a new algorithm that allocates but
is faster asymptotically.
Comparing rustc nightly with a local build of rustc as of this PR (results in seconds):
| N | real time before | real time after |
| - | - | - |
| 4_000 | 0.57 | 0.46 |
| 8_000 | 1.31 | 0.84 |
| 16_000 | 3.56 | 1.69 |
| 32_000 | 10.60 | 3.73 |
I've tuned up the numbers to make the effect larger than the startup noise of rustc, but the asymptotic difference should hold for smaller n as well.
Note: current state of the PR omits error messages if there are other errors present already. For now, I'm mainly interested in a perf run to study whether this issue is present at all. Please queue one for this PR. Thanks!
Mark `-1` as an available niche for file descriptors
Based on discussion from <https://internals.rust-lang.org/t/can-the-standard-library-shrink-option-file/12768>, the file descriptor `-1` is chosen based on the POSIX API designs that use it as a sentinel to report errors. A bigger niche could've been chosen, particularly on Linux, but would not necessarily be portable.
This PR also adds a test case to ensure that the -1 niche (which is kind of hacky and has no obvious test case) works correctly. It requires the "upper" bound, which is actually -1, to be expressed in two's complement.
Make BoundRegion have a kind of BoungRegionKind
Split from #76814
Also includes making `replace_escaping_bound_vars` only return `T`
Going to r? `@lcnr`
Feel free to reassign
or_patterns: implement :pat edition-specific behavior
cc #54883 `@joshtriplett`
This PR implements the edition-specific behavior of `:pat` wrt or-patterns, as determined by the crater runs and T-lang consensus in https://github.com/rust-lang/rust/issues/54883#issuecomment-745509090.
I believe this can unblock stabilization of or_patterns.
r? `@petrochenkov`
const_evaluatable_checked: fix occurs check
fixes#79615
this is kind of a hack because we use `TypeRelation` for both the `Generalizer` and the `ConstInferUnifier` but i am not sure if there is a useful way to disentangle this without unnecessarily duplicating some code.
The error in the added test is kind of unavoidable until we erase the unused substs of `ConstKind::Unevaluated`. We talked a bit about this in the cg lazy norm meeting (https://rust-lang.zulipchat.com/#narrow/stream/260443-project-const-generics/topic/lazy_normalization_consts)
Improve and fix diagnostics of exhaustiveness checking
Primarily, this fixes https://github.com/rust-lang/rust/issues/56379. This also fixes incorrect interactions between or-patterns and slice patterns that I discovered while working on #56379. Those two examples show the incorrect diagnostics:
```rust
match &[][..] {
[true] => {}
[true // detected as unreachable but that's not true
| false, ..] => {}
_ => {}
}
match (true, None) {
(true, Some(_)) => {}
(false, Some(true)) => {}
(true | false, None | Some(true // should be detected as unreachable
| false)) => {}
}
```
I did not measure any perf impact. However, I suspect that [`616ba9f`](https://github.com/rust-lang/rust/pull/80104/commits/616ba9f9f7f5845777a36e1a41a515e6c33a8776) should have a negative impact on large or-patterns. I'll see what the perf run says; I have optimization ideas up my sleeve if needed.
EDIT: I initially had a noticeable perf impact that I thought unavoidable. I then proceeded to avoid it x)
r? `@varkor`
`@rustbot` label +A-exhaustiveness-checking
passes: prohibit invalid attrs on generic params
Fixes#78957.
This PR modifies the `check_attr` pass so that attribute placement on generic parameters is checked for validity.
r? `@lcnr`
Rollup of 5 pull requests
Successful merges:
- #78164 (Prefer regions with an `external_name` in `approx_universal_upper_bound`)
- #80003 (Fix overflow when converting ZST Vec to VecDeque)
- #80023 (Enhance error message when misspelled label to value in break expression)
- #80046 (Add more documentation to `Diagnostic` and `DiagnosticBuilder`)
- #80109 (Remove redundant and unreliable coverage test results)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Prefer regions with an `external_name` in `approx_universal_upper_bound`
Fixes#75785
When displaying a MIR borrowcheck error, we may need to find an upper
bound for a region, which gives us a region to point to in the error
message. However, a region might outlive multiple distinct universal
regions, in which case the only upper bound is 'static
To try to display a meaningful error message, we compute an
'approximate' upper bound by picking one of the universal regions.
Currently, we pick the region with the lowest index - however, this
caused us to produce a suboptimal error message in issue #75785
This PR `approx_universal_upper_bound` to prefer regions with an
`external_name`. This causes us to prefer regions from function
arguments/upvars, which seems to lead to a nicer error message in some
cases.
Fixes#75785
When displaying a MIR borrowcheck error, we may need to find an upper
bound for a region, which gives us a region to point to in the error
message. However, a region might outlive multiple distinct universal
regions, in which case the only upper bound is 'static
To try to display a meaningful error message, we compute an
'approximate' upper bound by picking one of the universal regions.
Currently, we pick the region with the lowest index - however, this
caused us to produce a suboptimal error message in issue #75785
This PR `approx_universal_upper_bound` to prefer regions with an
`external_name`. This causes us to prefer regions from function
arguments/upvars, which seems to lead to a nicer error message in some
cases.
Move binder for dyn to each list item
This essentially changes `ty::Binder<&'tcx List<ExistentialTraitRef>>` to `&'tcx List<ty::Binder<ExistentialTraitRef>>`.
This is a first step in moving the `dyn Trait` representation closer to Chalk, which we've talked about in `@rust-lang/wg-traits.`
r? `@nikomatsakis`
Fix issue #78496
EarlyOtherwiseBranch finds MIR structures like:
```
bb0: {
...
_2 = discriminant(X)
...
switchInt(_2) -> [1_isize: bb1, otherwise: bb3]
}
bb1: {
...
_3 = discriminant(Y)
...
switchInt(_3) -> [1_isize: bb2, otherwise: bb3]
}
bb2: {...}
bb3: {...}
```
And transforms them into something like:
```
bb0: {
...
_2 = discriminant(X)
_3 = discriminant(Y)
_4 = Eq(_2, _3)
switchInt(_4) -> [true: bb4, otherwise: bb3]
}
bb2: {...} // unchanged
bb3: {...} // unchanged
bb4: {
switchInt(_2) -> [1_isize: bb2, otherwise: bb3]
}
```
But that is not always a safe thing to do -- sometimes the early `otherwise` branch is necessary so the later block could assume the value of `discriminant(X)`.
I am not totally sure what's the best way to detect that, but fixing #78496 should be easy -- we just check if `X` is a sub-expression of `Y`. A more precise test might be to check if `Y` contains a `Downcast(1)` of `X`, but I think this might be good enough.
Fix#78496
Allow `since="TBD"` for rustc_deprecated
Closes#78381.
This PR only affects `#[rustc_deprecated]`, not `#[deprecated]`, so there is no effect on any stable language feature.
Likewise this PR only implements `since="TBD"`, it does not actually tag any library functions with it, so there is no effect on any stable API.
Overview of changes:
* `rustc_middle/stability.rs`:
* change `deprecation_in_effect` function to return `false` when `since="TBD"`
* tidy up the compiler output when a deprecated item has `since="TBD"`
* `rustc_passes/stability.rs`:
* allow `since="TBD"` to pass the sanity check for stable_version < deprecated_version
* refactor the "invalid stability version" and "invalid deprecation version" error into separate errors
* rustdoc: make `since="TBD"` message on a deprecated item's page match the command-line deprecation output
* tests:
* test rustdoc output
* test that the `deprecated_in_future` lint fires when `since="TBD"`
* test the new "invalid deprecation version" error message
Implement if-let match guards
Implements rust-lang/rfcs#2294 (tracking issue: #51114).
I probably should do a few more things before this can be merged:
- [x] Add tests (added basic tests, more advanced tests could be done in the future?)
- [x] Add lint for exhaustive if-let guard (comparable to normal if-let statements)
- [x] Fix clippy
However since this is a nightly feature maybe it's fine to land this and do those steps in follow-up PRs.
Thanks a lot `@matthewjasper` ❤️ for helping me with lowering to MIR! Would you be interested in reviewing this?
r? `@ghost` for now
Take into account negative impls in "trait item not found" suggestions
This removes the suggestion to implement a trait for a type when that type already has a negative implementation for the trait, and replaces it with a note to point out that the trait is explicitely unimplemented, as suggested by `@scottmcm.`
Helps with #79683.
r? `@scottmcm` do you want to review this?
consider assignments of union field of ManuallyDrop type safe
Assigning to `Copy` union fields is safe because that assignment will never drop anything. However, with https://github.com/rust-lang/rust/pull/77547, unions may also have `ManuallyDrop` fields, and their assignments are currently still unsafe. That seems unnecessary though, as assigning `ManuallyDrop` does not drop anything either, and is thus safe even for union fields.
I assume this will at least require FCP.
Properly capture trailing 'unglued' token
If we try to capture the `Vec<u8>` in `Option<Vec<u8>>`, we'll
need to capture a `>` token which was 'unglued' from a `>>` token.
The processing of unglueing a token for parsing purposes bypasses the
usual capturing infrastructure, so we currently lose the trailing `>`.
As a result, we fall back to the reparsed `TokenStream`, causing us to
lose spans.
This commit makes token capturing keep track of a trailing 'unglued'
token. Note that we don't need to care about unglueing except at the end
of the captured tokens - if we capture both the first and second unglued
tokens, then we'll end up capturing the full 'glued' token, which
already works correctly.
