Add experimental Iterator::contains #135018

leb-kuchen · 2025-01-02T10:31:22Z

tracking issue
This is the continuation of the abandoned PR.

rustbot · 2025-01-02T10:31:31Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @joboet (or someone else) some time within the next two weeks.

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clubby789 · 2025-01-02T11:26:43Z

library/core/src/slice/iter/macros.rs

@@ -289,6 +289,16 @@ macro_rules! iterator {
                false
            }

+            fn contains<Q: ?Sized>(&mut self, item: Q) -> bool


Why is this reimplemented when it uses the same code as the default impl?

It is to use SliceContains as a optimization later, but the trait has different trait bounds, so this requires further changes to the trait.

You shouldn't add an empty specialization like this, either actually specialize it or leave it out for now.

Noratrieb · 2025-01-02T12:04:11Z

library/core/src/iter/traits/iterator.rs

@@ -2770,6 +2770,39 @@ pub trait Iterator {
        self.try_fold((), check(f)) == ControlFlow::Break(())
    }

+    /// Returns `true` if the iterator contains a value.


For consistency with other methods

Suggested change

/// Returns `true` if the iterator contains a value.

/// Tests whether a value is contained in the iterator.

leb-kuchen · 2025-01-02T12:28:02Z

There is the itertools breakage with rust analyzer and the UI tests have still been failing.

rust-log-analyzer · 2025-01-02T12:41:56Z

The job mingw-check failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

    Checking load-cargo v0.0.0 (/checkout/src/tools/rust-analyzer/crates/load-cargo)
error: a method with this name may be added to the standard library in the future
   --> src/tools/rust-analyzer/crates/ide-assists/src/handlers/bool_to_enum.rs:384:48
    |
384 |     if !bin_expr.lhs()?.syntax().descendants().contains(name.syntax()) {
    |
    = warning: once this associated item is added to the standard library, the ambiguity may cause an error or change in behavior!
    = note: for more information, see issue #48919 <https://github.com/rust-lang/rust/issues/48919>
    = help: call with fully qualified syntax `itertools::Itertools::contains(...)` to keep using the current method
    = help: call with fully qualified syntax `itertools::Itertools::contains(...)` to keep using the current method
    = note: `-D unstable-name-collisions` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(unstable_name_collisions)]`
help: add `#![feature(iter_contains)]` to the crate attributes to enable `std::iter::Iterator::contains`
   --> src/tools/rust-analyzer/crates/ide-assists/src/lib.rs:63:1
    |
63  + #![feature(iter_contains)]

error: a method with this name may be added to the standard library in the future
   --> src/tools/rust-analyzer/crates/ide-assists/src/handlers/bool_to_enum.rs:450:41
    |
    |
450 |     if !receiver.syntax().descendants().contains(name.syntax()) {
    |
    = warning: once this associated item is added to the standard library, the ambiguity may cause an error or change in behavior!
    = note: for more information, see issue #48919 <https://github.com/rust-lang/rust/issues/48919>
    = help: call with fully qualified syntax `itertools::Itertools::contains(...)` to keep using the current method
    = help: call with fully qualified syntax `itertools::Itertools::contains(...)` to keep using the current method
help: add `#![feature(iter_contains)]` to the crate attributes to enable `std::iter::Iterator::contains`
   --> src/tools/rust-analyzer/crates/ide-assists/src/lib.rs:63:1
    |
63  + #![feature(iter_contains)]

error: could not compile `ide-assists` (lib) due to 2 previous errors
warning: build failed, waiting for other jobs to finish...
error: could not compile `ide-assists` (lib test) due to 2 previous errors

zachs18 · 2025-01-03T15:39:29Z

library/core/src/iter/traits/iterator.rs

+    /// on collections that have a `.contains()` or `.contains_key()` method (such as
+    /// `HashMap` or `BtreeSet`, using those methods directly will be faster.


Suggested change

/// on collections that have a `.contains()` or `.contains_key()` method (such as

/// `HashMap` or `BtreeSet`, using those methods directly will be faster.

/// on collections that have a `.contains()` or `.contains_key()` method (such as

/// `HashMap` or `BtreeSet`), using those methods directly will be faster.

joboet · 2025-01-03T18:24:41Z

r? libs-api

rustbot assigned joboet Jan 2, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jan 2, 2025