Add future incompatibility lint for array.into_iter()
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(My way was a hack; a real lint like this is a much better plan.) I think a lint here is definitely valuable. Could even run it on slices as well, since in theory we might want to be able to use unsized locals to have |
scottmcm
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Nov 1, 2019
cramertj
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I just pushed a new version. I think it's fine now. My code now checks if the original expr type is an array and if autoref coercion happened. I think this should exactly what we want. At least the UI test now works as you expected. |
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The job Click to expand the log.I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact |
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Can someone tell me what I'm doing wrong here? |
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It looks like the future-compat warnings include another warning (?) within the notes. Try changing the annotations like this: |
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Does this lint catch this example? trait IntoIteratorExt: IntoIterator + Sized {
fn into_iter_first(self) -> Option<Self::Item> {
self.into_iter().next()
}
}
impl<T: IntoIterator> IntoIteratorExt for T {}
fn foo(value: Option<&i32>) {
println!("{}", value.unwrap());
}
fn main() {
foo([1,2,3].into_iter_first());
}This could potentially be split over multiple crates. |
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@TethysSvensson Nope, the lint does not catch that. I'd guess this is a lot more complicated to test for. As I won't be able to look into this in the next days, I'd say we merge this as is (if everything else is OK) to get it into 1.40 still. Unless it's too late for that anyway... From the regressed crates that I looked at, no crate failed due to something like you are suggesting. You are absolutely right that this would break, but as far as I know, we haven't seen this yet. Maybe we can – after merging this PR – create a PR that denies-by-default this lint and run crater on the regressed crates again. By checking how many still regress (this time due to the lint), we can see how many regressions the lint doesn't catch. |
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| use crate::lint::{LateContext, LateLintPass, LintArray, LintContext, LintPass}; | |||
| use rustc::{ | |||
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@bors r+ |
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📌 Commit 51a4cd0fc62345ccdf4b698b3b283fcd193e9d59 has been approved by |
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@bors r- |
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As we might want to add `IntoIterator` impls for arrays in the future, and since that introduces a breaking change, this lint warns and suggests using `iter()` instead (which is shorter and more explicit).
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Pushed again. Sorry for delay. Should be green now, I tested locally. |
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@bors r=matthewjasper |
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…t, r=matthewjasper Add future incompatibility lint for `array.into_iter()` This is for rust-lang#65819. This lint warns when calling `into_iter` on an array directly. That's because today the method call resolves to `<&[T] as IntoIterator>::into_iter` but that would change when adding `IntoIterator` impls for arrays. This problem is discussed in detail in rust-lang#65819. We still haven't decided how to proceed exactly, but it seems like adding a lint is a good idea regardless? Also: this is the first time I implement a lint, so there are probably a lot of things I can improve. I used a different strategy than @scottmcm describes [here](rust-lang#65819 (comment)) since I already started implementing this before they commented. ### TODO - [x] Decide if we want this lint -> apparently [we want](rust-lang#65819 (comment)) - [x] Open a lint-tracking-issue and add the correct issue number in the code -> rust-lang#66145
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Rollup of 5 pull requests Successful merges: - #59789 (Revert two unapproved changes to rustc_typeck.) - #65752 (Use structured suggestions for missing associated items) - #65884 (syntax: ABI-oblivious grammar) - #65974 (A scheme for more macro-matcher friendly pre-expansion gating) - #66017 (Add future incompatibility lint for `array.into_iter()`) Failed merges: - #66056 (rustc_metadata: Some reorganization of the module structure) r? @ghost
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Well that deprecates the |
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This lint was uplifted/reimplemented by rustc. Rustup to rust-lang/rust#66017
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This lint was uplifted/reimplemented by rustc. Rustup to rust-lang/rust#66017
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This lint was uplifted/reimplemented by rustc. Rustup to rust-lang/rust#66017
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475: Trait impls for tuples of arity <= 12 r=jswrenn a=jswrenn I stopped at 12, because that's where libcore stops. fixes #428 fixes #398 476: Undeprecate and optimize `fold_while` r=jswrenn a=jswrenn Prompted by #469. 479: fix compiler warning on array.into_iter() r=jswrenn a=dmitris Fix the compile warnings listed below by changing `into_iter()` invocation to `iter()` in the `impl_zip_iter` macro as recommended in rust-lang/rust#66145. For additional background, see also rust-lang/rust#65819 and rust-lang/rust#66017 (the latter is the linter change producing the warning). ``` $ cargo build Compiling itertools v0.9.0 (/Users/dsavints/dev/hack/github.com/rust-itertools/itertools) warning: this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter` (due to autoref coercions), but that might change in the future when `IntoIterator` impls for arrays are added. --> src/ziptuple.rs:111:47 | 111 | let size = *[$( $B.len(), )*].into_iter().min().unwrap(); | ^^^^^^^^^ help: use `.iter()` instead of `.into_iter()` to avoid ambiguity: `iter` ... 128 | impl_zip_iter!(A); | ------------------ in this macro invocation | = note: `#[warn(array_into_iter)]` on by default = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! = note: for more information, see issue #66145 <rust-lang/rust#66145> = note: this warning originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info) warning: this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter` (due to autoref coercions), but that might change in the future when `IntoIterator` impls for arrays are added. --> src/ziptuple.rs:111:47 | 111 | let size = *[$( $B.len(), )*].into_iter().min().unwrap(); | ^^^^^^^^^ help: use `.iter()` instead of `.into_iter()` to avoid ambiguity: `iter` ... 129 | impl_zip_iter!(A, B); | --------------------- in this macro invocation | = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! = note: for more information, see issue #66145 <rust-lang/rust#66145> = note: this warning originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info) ``` Co-authored-by: Jack Wrenn <[email protected]> Co-authored-by: Dmitry Savintsev <[email protected]>
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This is for #65819. This lint warns when calling
into_iteron an array directly. That's because today the method call resolves to<&[T] as IntoIterator>::into_iterbut that would change when addingIntoIteratorimpls for arrays. This problem is discussed in detail in #65819.We still haven't decided how to proceed exactly, but it seems like adding a lint is a good idea regardless?
Also: this is the first time I implement a lint, so there are probably a lot of things I can improve. I used a different strategy than @scottmcm describes here since I already started implementing this before they commented.
TODO
array_into_iter#66145