inherit #[align] from trait method prototypes

[folkertdev]

@workingjubilee this seems straightforward enough. Now that we're planning to make -Cmin-function-alignment a target modifier, I don't think there are any cross-crate complications here?

@Jules-Bertholet is this the behavior you had in mind? In particular the inheritance of the attribute of a default impl is maybe a bit unintuitive at first? (but I think it's ok if that behavior is explicitly documented).

r? ghost

[Jules-Bertholet]

Maybe add a few tests for multiple align attributes on the same item, combined with traits? Other than that and my 1 comment, LGTM

[workingjubilee]

@workingjubilee this seems straightforward enough. Now that we're planning to make -Cmin-function-alignment a target modifier, I don't think there are any cross-crate complications here?

@folkertdev I can't promise this won't somehow flow back into concerns for the implementation of the feature we're stabilizing in that PR, but I agree this should be enough for here.

[workingjubilee]

In particular, "there is one universal rule for how this trait's code should be aligned" reduces the number of things we need to worry about when trying to correctly instantiate the alignment of that code's functions.

[folkertdev]

Sure, we'll see how that develops.

At least we've thought about this now, and have something concrete to create tests against if the need arises.

r? @workingjubilee

[rustbot]

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[rustbot]

Some changes occurred in compiler/rustc_codegen_ssa

cc @WaffleLapkin

Some changes occurred in compiler/rustc_codegen_ssa/src/codegen_attrs.rs

cc @jdonszelmann

[workingjubilee]

@bors r+

[bors]

📌 Commit bcf5105 has been approved by workingjubilee

It is now in the queue for this repository.