[Issue 21479] ternary operator returns wrong val with ref return

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21479

--- Comment #3 from Iain Buclaw <ibuclaw at gdcproject.org> ---
One underlying issue with the constructed AST is that Side.left is not constant
propagated, this differs with other kinds of expressions/statements that use
enum members.  They always send expanded literals to the back-end.

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