Remove unneeded lifetime bound from signature of BTreeSet::extract_if

[dtolnay]

One way to observe the difference between these signatures, using 0 explicit lifetimes and 0 contrived where-clauses:

use std::collections::btree_set::{BTreeSet, ExtractIf};
use std::ops::RangeFull;

fn repro(
    set: &mut BTreeSet<i32>,
    predicate: impl Fn(i32) -> bool,
) -> ExtractIf<i32, RangeFull, impl FnMut(&i32) -> bool> {
    set.extract_if(.., move |x| predicate(*x))
}

Before:

error[E0311]: the parameter type `impl Fn(i32) -> bool` may not live long enough
 --> src/lib.rs:8:5
  |
5 |     set: &mut BTreeSet<i32>,
  |          ------------------ the parameter type `impl Fn(i32) -> bool` must be valid for the anonymous lifetime defined here...
...
8 |     set.extract_if(.., move |x| predicate(*x))
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `impl Fn(i32) -> bool` will meet its required lifetime bounds
  |
help: consider adding an explicit lifetime bound
  |
4 ~ fn repro<'a>(
5 ~     set: &'a mut BTreeSet<i32>,
6 ~     predicate: impl Fn(i32) -> bool + 'a,
7 ~ ) -> ExtractIf<'a, i32, RangeFull, impl FnMut(&i32) -> bool> {
  |

After: compiles successfully.

• Tracking issue: Tracking Issue for {BTreeMap,BTreeSet}::extract_if #70530

[rustbot]

r? @ibraheemdev

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[m-ou-se]

@bors r+ rollup

[bors]

📌 Commit dac9d78 has been approved by m-ou-se

It is now in the queue for this repository.