CODEWITHSUNDEEP
scala
Krever
Krever

Reputation: 1467

Can you enforce exhaustiveness of Map keys in scala?

Let's assume we have a map indexed by enum values like this 

sealed trait A
case object B extends A
case object C extends A

type SafeMap = Map[A, String]

Would it be possible to somehow enforce the exhaustiveness of such map? Maybe with dependent types? If not in Scala than Idris is interesting as well.

To clarify, I would like to have a generic constraint for any ADT that check that Map has an entry defined for each variant of ADT.

Upvotes: 1

Views: 230

Answers (1)

Dominic Egger
Dominic Egger

Reputation: 1016

well a Map[A,String] for an ADT A is pretty much a function A => String

You can do 

def foo(a:A):String = a match {
    case ...
}

with the fatal-warning flag for the compiler (else non-exhaustive patternmatches are only warnings) this should get you pretty far.

PS: you should probably make your case classes/object final

Upvotes: 4

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