We should use a () constant instead of `Rvalue::Aggregate(box AggregateKind::Tuple, vec![])`.

[eddyb]

This should be changed to return a () Operand::Const (not Rvalue::Use of that operand):

rust/src/librustc_mir_build/build/misc.rs

Lines 35 to 37 in 39b6253

	crate fn unit_rvalue(&mut self) -> Rvalue<'tcx> {
	Rvalue::Aggregate(box AggregateKind::Tuple, vec![])
	}

These two other places should switch to a () Rvalue::Use(Operand::Const(...)):

rust/src/librustc_mir_build/build/cfg.rs

Line 66 in 39b6253

Rvalue::Aggregate(box AggregateKind::Tuple, vec![]),

rust/src/librustc_mir/transform/promote_consts.rs

Line 838 in 39b6253

let unit = Rvalue::Aggregate(box AggregateKind::Tuple, vec![]);

This issue has been assigned to @lcnr via this comment.

[lcnr]

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