Use new const_fn_trait_bound feature to fix build on latest nightly

[phil-opp]

Feature gate introduced in rust-lang/rust#84310.

Unfortunately, unknown feature gates lead to errors so that this change errors on older nightlies. For this reason, I think we should at least wait until the common rustfmt component is fixed on nightly again because then everyone should be able to update. See https://rust-lang.github.io/rustup-components-history/ for component availability.

Fixes #252

[phil-opp]

Prepublished as v0.14.1-beta in case someone is already using the latest nightly.

[josephlr]

This looks great!! I'm glad the catch-all const_fn feature is finally going away.

Given that this change will break all users on previous nighties, should we update the rust-toolchain file to point to a specific nightly?

[phil-opp]

Yeah, me too! I hope that this means less nightly breakage in the future.

Given that this change will break all users on previous nighties, should we update the rust-toolchain file to point to a specific nightly?

Not sure what the advantage of that would be. The CI already uses the latest nightly and it wouldn't help people that use x86_64 as a dependency. It would help people on older nightlies that try to contribute to this crate, but the disadvantage is that our CI would no longer test with the latest nightly then.

[josephlr]

Given that this change will break all users on previous nighties, should we update the rust-toolchain file to point to a specific nightly?

Not sure what the advantage of that would be. The CI already uses the latest nightly and it wouldn't help people that use x86_64 as a dependency. It would help people on older nightlies that try to contribute to this crate, but the disadvantage is that our CI would no longer test with the latest nightly then.

That makes sense. SGTM for leaving it as is.

[josephlr]

Looks like the 2021-05-06 nightly has fixed components. @phil-opp should we merge this?

[HTGAzureX1212]

republished as v0.14.1-beta in case someone is already using the latest nightly.

Thanks, I will update to the pre-release version of the crate now probably.

[phil-opp]

Looks like the 2021-05-06 nightly has fixed components. @phil-opp should we merge this?

Yes, thanks for the ping!

[phil-opp]

Published as v0.14.1.