Tracking Issue for `or_insert_with_key` feature

[ChaiTRex]

Steps

• Implementation in std (Add or_insert_with_key to Entry of HashMap/BTreeMap #70996)
• Merge into std
• Implementation in hashbrown crate (Add or_insert_with_key to Entry of HashMap hashbrown#152)
• Merge into hashbrown
• Stabilization (Stabilize or_insert_with_key #78083)
• Make pull request with documentation changes from ChaiTRex/hashbrown to rust-lang/hashbrown (Imported new documentation for .or_insert_with_key hashbrown#217)
• Close old issue requesting feature (Add hash_map::Entry.or_insert_with_key() method rfcs#1202)

[jonas-schievink]

* Implementation in `std` (#70966)

That seems like the wrong PR

[ChaiTRex]

@jonas-schievink Thank you. Corrected.

Also, added a 2015 issue that requested this feature so that it can be closed if this is accepted.

[ChaiTRex]

Merged into hashbrown (rust-lang/hashbrown#152) and into std as unstable (#70996).

[a1phyr]

What does this feature need to be stabilized ?

[ChaiTRex]

This is my first stabilization report, so please let me know if it's insufficient.

Stabilization report

Summary

This allows inserting key-derived values when a HashMap/BTreeMap entry is vacant.

The difference between this and .or_insert_with(|| ... ) is that this provides a reference to the key to the closure after it is moved with .entry(key_being_moved), avoiding the need to copy or clone the key.

Examples

• Doc test
• Rust book chapter 13 memoization exercise

Edge cases

I cannot think of any edge cases.

Stabilization pull request

The stabilization pull request is #78083