adjust const_eval_select documentation#91325
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bors merged 2 commits intorust-lang:masterfrom Dec 11, 2021
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"The Rust compiler assumes" indicates that this is language UB, but I don't think that is a good idea. This UB would be very hard to test for and looks like a way-too-big footgun. @oli-obk suggested this is meant to be more like "library UB", so I tried to adjust the docs accordingly.
I also removed all references to "referential transparency". That is a rather vague concept used to mean many different things, and I honestly have no idea what exactly is meant by it in this specific instance. But I assume @fee1-dead had in their mind a property that all
const fncode upholds, so by demanding that the runtime code and the const-time code are observably equivalent, whatever that property is would also be enforced here.Cc @rust-lang/wg-const-eval