add test ensuring simd codegen checks don't run when a static assertion failed

[RalfJung]

stdarch relies on this to ensure that SIMD indices are in bounds.

I would love to know why this works, but I can't figure out where codegen decides to not codegen a function if a required-const does not evaluate. @oli-obk @bjorn3 do you have any idea?

[rustbot]

r? @pnkfelix

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[RalfJung]

We do have this:

rust/compiler/rustc_monomorphize/src/collector.rs

Lines 824 to 832 in 9669934

	Ok(v) => v,
	Err(ErrorHandled::Reported(..)) => return,
	Err(ErrorHandled::TooGeneric(..)) => span_bug!(
	self.body.source_info(location).span,
	"collection encountered polymorphic constant: {:?}",
	const_
	),
	};
	collect_const_value(self.tcx, val, self.output);

This will show the const-error, but the collector keeps going. I guess somewhere it still then check if there was any error and stop before starting codegen? Is that this line here?

rust/compiler/rustc_monomorphize/src/partitioning.rs

Line 1117 in 3f27e4b

tcx.dcx().abort_if_errors();

So I think the key point is there's actually two phases here: collecting all the items, and then codegen'ing them. Const errors are "collection-time errors", not "codegen-time errors".

[rustbot]

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

[pnkfelix]

@bors r+ rollup

[bors]

📌 Commit d765fb8 has been approved by pnkfelix

It is now in the queue for this repository.