Definition of "exhaustive" for switch statements?

[Lantua]

@jrose

if the where conditions have side effects, they must not be evaluated if the pattern doesn't match

Isn't it similar to this post (below), that the actual evaluation order is undefined? Or are they different things?

What's the harm in not knowing that a switch statement's pattern-matching order is undefined?

I just read this in “The Swift Programming Language”: (5.2 beta, p 1005) Although the actual execution order of pattern-matching operations, and in particular the evaluation order of patterns in cases, is unspecified, pattern matching in a switch statement behaves as if the evaluation is performed in source order—that is, the order in which they appear in source code. As a result, if multiple cases contain patterns that evaluate to the same value, and thus can match the value of the control exp…