clubby789
2f882c014f
Specify that break cannot be used outside of loop *or* labeled block
2022-11-05 01:12:58 +00:00
Maybe Waffle
13b67fb9d2
bless ui tests
2022-10-01 10:03:06 +00:00
Joshua Nelson
31e39446ec
Stabilize #![feature(label_break_value)]
...
# Stabilization proposal
The feature was implemented in https://github.com/rust-lang/rust/pull/50045 by est31 and has been in nightly since 2018-05-16 (over 4 years now).
There are [no open issues][issue-label] other than the tracking issue. There is a strong consensus that `break` is the right keyword and we should not use `return`.
There have been several concerns raised about this feature on the tracking issue (other than the one about tests, which has been fixed, and an interaction with try blocks, which has been fixed).
1. nrc's original comment about cost-benefit analysis: https://github.com/rust-lang/rust/issues/48594#issuecomment-422235234
2. joshtriplett's comments about seeing use cases: https://github.com/rust-lang/rust/issues/48594#issuecomment-422281176
3. withoutboats's comments that Rust does not need more control flow constructs: https://github.com/rust-lang/rust/issues/48594#issuecomment-450050630
Many different examples of code that's simpler using this feature have been provided:
- A lexer by rpjohnst which must repeat code without label-break-value: https://github.com/rust-lang/rust/issues/48594#issuecomment-422502014
- A snippet by SergioBenitez which avoids using a new function and adding several new return points to a function: https://github.com/rust-lang/rust/issues/48594#issuecomment-427628251 . This particular case would also work if `try` blocks were stabilized (at the cost of making the code harder to optimize).
- Several examples by JohnBSmith: https://github.com/rust-lang/rust/issues/48594#issuecomment-434651395
- Several examples by Centril: https://github.com/rust-lang/rust/issues/48594#issuecomment-440154733
- An example by petrochenkov where this is used in the compiler itself to avoid duplicating error checking code: https://github.com/rust-lang/rust/issues/48594#issuecomment-443557569
- Amanieu recently provided another example related to complex conditions, where try blocks would not have helped: https://github.com/rust-lang/rust/issues/48594#issuecomment-1184213006
Additionally, petrochenkov notes that this is strictly more powerful than labelled loops due to macros which accidentally exit a loop instead of being consumed by the macro matchers: https://github.com/rust-lang/rust/issues/48594#issuecomment-450246249
nrc later resolved their concern, mostly because of the aforementioned macro problems.
joshtriplett suggested that macros could be able to generate IR directly
(https://github.com/rust-lang/rust/issues/48594#issuecomment-451685983 ) but there are no open RFCs,
and the design space seems rather speculative.
joshtriplett later resolved his concerns, due to a symmetry between this feature and existing labelled break: https://github.com/rust-lang/rust/issues/48594#issuecomment-632960804
withoutboats has regrettably left the language team.
joshtriplett later posted that the lang team would consider starting an FCP given a stabilization report: https://github.com/rust-lang/rust/issues/48594#issuecomment-1111269353
[issue-label]: https://github.com/rust-lang/rust/issues?q=is%3Aissue+is%3Aopen+label%3AF-label_break_value+
## Report
+ Feature gate:
- d695a497bb/src/test/ui/feature-gates/feature-gate-label_break_value.rs6b2d3d5f3c/compiler/rustc_parse/src/parser/diagnostics.rs (L2629)f65bf0b2bb/compiler/rustc_resolve/src/diagnostics.rs (L749)f65bf0b2bb/compiler/rustc_resolve/src/diagnostics.rs (L1001)111df9e6ed/compiler/rustc_passes/src/loops.rs (L254)d695a497bb/compiler/rustc_parse/src/parser/expr.rs (L2079)d695a497bb/compiler/rustc_parse/src/parser/expr.rs (L1569)https://github.com/rust-lang/rust/blob/master/src/test/ui/label/label_break_value_continue.rs
- https://github.com/rust-lang/rust/blob/master/src/test/ui/label/label_break_value_unlabeled_break.rs
- https://github.com/rust-lang/rust/blob/master/src/test/ui/label/label_break_value_illegal_uses.rs
- https://github.com/rust-lang/rust/blob/master/src/test/ui/lint/unused_labels.rs
- https://github.com/rust-lang/rust/blob/master/src/test/ui/run-pass/for-loop-while/label_break_value.rs
## Interactions with other features
Labels follow the hygiene of local variables.
label-break-value is permitted within `try` blocks:
```rust
let _: Result<(), ()> = try {
'foo: {
Err(())?;
break 'foo;
}
};
```
label-break-value is disallowed within closures, generators, and async blocks:
```rust
'a: {
|| break 'a
//~^ ERROR use of unreachable label `'a`
//~| ERROR `break` inside of a closure
}
```
label-break-value is disallowed on [_BlockExpression_]; it can only occur as a [_LoopExpression_]:
```rust
fn labeled_match() {
match false 'b: { //~ ERROR block label not supported here
_ => {}
}
}
macro_rules! m {
($b:block) => {
'lab: $b; //~ ERROR cannot use a `block` macro fragment here
unsafe $b; //~ ERROR cannot use a `block` macro fragment here
|x: u8| -> () $b; //~ ERROR cannot use a `block` macro fragment here
}
}
fn foo() {
m!({});
}
```
[_BlockExpression_]: https://doc.rust-lang.org/nightly/reference/expressions/block-expr.html
[_LoopExpression_]: https://doc.rust-lang.org/nightly/reference/expressions/loop-expr.html
2022-08-23 21:14:12 -05:00
Yiming Lei
9815667b8b
implement #98982
...
when loop as tail expression for miss match type E0308 error, recursively get
the return statement and add diagnostic information on it
use rustc_hir::intravisit to collect the return expression
modified: compiler/rustc_typeck/src/check/coercion.rs
new file: src/test/ui/typeck/issue-98982.rs
new file: src/test/ui/typeck/issue-98982.stderr
2022-08-05 10:28:00 -07:00
Michael Goulet
01b2379e49
Mention first and last macro in backtrace
2022-07-19 03:07:54 +00:00
Camille GILLOT
a265c49b25
Rebase fallout.
2022-06-02 19:24:32 +02:00
Joshua Nelson
cd63b22e80
Add more tests for label-break-value
2022-05-03 14:09:52 -05:00
Caio
41d9abd76c
Move some tests to more reasonable directories
2021-11-18 12:09:34 -03:00
Caio
ab5434f9b8
Move some tests to more reasonable directories
2021-11-14 14:38:42 -03:00
Caio
7fd15f0900
Move some tests to more reasonable directories
2021-11-06 15:35:20 -03:00
est31
6550021124
Remove box syntax from most places in src/test outside of the issues dir
2021-09-26 04:07:44 +02:00
Caio
e7e93717ce
Move some tests to more reasonable directories
2021-02-16 21:22:21 -03:00
Caio
2bb4a694d1
Move some tests to more reasonable directories
2021-01-31 19:46:46 -03:00
Mark Rousskov
c205f6a06a
Remove mem::uninitalized from tests
...
This purges uses of uninitialized where possible from test cases. Some
are merely moved over to the equally bad pattern of
MaybeUninit::uninit().assume_init() but with an annotation that this is
"the best we can do".
2019-12-22 21:58:12 -05:00
Niko Matsakis
1719337d02
Revert "Remove #![feature(never_type)] from tests."
...
This reverts commit 8f6197f39f
2019-12-14 09:01:04 -05:00
Mazdak Farrokhzad
56f830e292
Rollup merge of #66325 - BartMassey:master, r=joshtriplett
...
Change unused_labels from allow to warn
Fixes #66324 , making the unused_labels lint warn instead of allow by default. I'm told @rust-lang/lang will need to review this, and perhaps will want to do a crater run.
2019-12-08 03:39:43 +01:00
Mazdak Farrokhzad
8f6197f39f
Remove #![feature(never_type)] from tests.
...
Also remove `never_type` the feature-gate test.
2019-11-21 14:55:32 +01:00
Bart Massey
ed56f86781
Cleaned up unused labels
...
Deleted unused labels from compiler and fixed or allowed
unused labels in tests. This patch removes some gratuitous
unused labels and turns off the warning for unused labels
that are a necessary part of tests. This will permit
setting the `unused_labels` lint to `warn`.
2019-11-15 16:31:30 -08:00
Mazdak Farrokhzad
1fb8cfb481
Organize never_type tests
...
Also move {run-fail -> ui}/never_type
2019-10-15 16:58:14 +02:00
Vadim Petrochenkov
9be35f82c1
tests: Move run-pass tests without naming conflicts to ui
2019-07-27 18:56:16 +03:00
