Tracking Issue for `const_fn_trait_bound`

[PatchMixolydic]

This is a tracking issue for trait bounds on const fns. The feature gate for the issue is #![feature(const_fn_trait_bound)]. This is not to be confused with the "trait impl must be const in const contexts" syntax, ~const Trait, which is a part of const_trait_impl and is tracked in #67792.

About tracking issues

Tracking issues are used to record the overall progress of implementation.
They are also used as hubs connecting to other relevant issues, e.g., bugs or open design questions.
A tracking issue is however not meant for large scale discussion, questions, or bug reports about a feature.
Instead, open a dedicated issue for the specific matter and add the relevant feature gate label.

Steps

• Implement the feature (couldn't find the implementation PR; const_fn_trait_bound was split from const_fn in further split up const_fn feature flag #84310)
• Adjust documentation (see instructions on rustc-dev-guide) Update const_eval.md for feature stabilization reference#1166
• Stabilization PR (see instructions on rustc-dev-guide) Stabilize const_fn_fn_ptr_basics, const_fn_trait_bound, and const_impl_trait #93827

Unresolved Questions

• Stabilization error E0658 is trivially bypassed #90912

Implementation history

• #????? - Implementation
• further split up const_fn feature flag #84310 - Split const_fn_trait_bound into its own feature gate

@rustbot modify labels +A-const-fn +A-traits

[fee1-dead]

cc @rust-lang/wg-const-eval: Should we remove this feature because of #90912?

[oli-obk]

Yes, together with function pointers and trait objects. We just need a stabilization PR and a summary for the lang team

[eholk]

I have a stabilization PR at #93827 and a documentation PR now at rust-lang/reference#1166.