Scala creating an instance of type alias

Question

I am wondering how to create an instance of type alias. More specifically this:

type Graph = scala.collection.mutable.Map[Statement, Statement]

I tried this but I get a type error saying Map[Statement, Statement] is not equivalent to Graph:

val graph: Graph = Map[Statement, Statement]().asInstanceOf[Graph]

Is this (i.e. creating a type alias) anti-pattern in Scala?

I can't reproduce with simple types in Scala. Is it possible you're accidentally using scala.collection.immutable.Map in the second snippet? — Silvio Mayolo
– Silvio Mayolo, Commented Feb 18, 2021 at 3:52
Honestly, it's a common mistake (mutable vs immutable collections of the same name). I'm glad there's a question on here now so others can clear it up. — Silvio Mayolo
– Silvio Mayolo, Commented Feb 18, 2021 at 21:19

jwvh · Accepted Answer · 2021-02-18 03:53:19Z

6

Map[?,?] is always immutable except when an import might shadow it.

This works:

val graph: Graph = collection.mutable.Map[Statement, Statement]()

answered Feb 18, 2021 at 3:53

jwvh

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