Auto merge of #13319 - emilio:constellation-refactoring, r=Ms2ger

constellation: Minor refactoring to aid legibility.

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Two things changed, on one hand, avoid a dumb if chain that could be more
idiomatically written with a match expression, and also avoiding use map() to
change state.

In general I'm pretty surprised for our lack of error reporting in this
critical code, but that's not the purpose of this PR.

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