Implement BinaryHeap::pop_if()

[max-heller]

Implementation of #151828

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[max-heller]

I'm getting errors compiling an alloctest test for pop_if():

  error[E0658]: use of unstable library feature `binary_heap_pop_if`
  Error:    --> alloctests/tests/collections/binary_heap.rs:145:35
      |
  145 |     while let Some(popped) = heap.pop_if(|x| *x > 2) {
      |                                   ^^^^^^
      |
      = note: see issue #151828 <https://github.com/rust-lang/rust/issues/151828> for more information
      = help: add `#![feature(binary_heap_pop_if)]` to the crate attributes to enable

I added #![feature(binary_heap_pop_if)] to alloctest/lib.rs alongside a large number of other #![feature] attributes, not sure what I'm missing.

[joboet]

Ah, it took me a while to figure out the CI failure...

View changes since this review

[joboet]

peek is just a bit nicer.

Suggested change

	let first = self.data.first()?;
	let first = self.peek()?;

[joboet]

This is the wrong lib.rs, you'll need to add the feature to alloctests/src/lib.rs instead. We use this lib.rs only for running the doctests and internal tests of alloc (I can't remember why alloc can't be tested directly just now, but there was some reason).

[max-heller]

That did it, thanks!

[joboet]

You'll need to add the feature here too, otherwise the doctest will fail 😉

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[max-heller]

Thanks for the review!
@rustbot ready

[jhpratt]

@bors r=jhpratt,joboet rollup

[rust-bors]

📌 Commit bae7a19 has been approved by jhpratt,joboet

It is now in the queue for this repository.