mirror of https://github.com/sbt/sbt.git
34 lines
1.1 KiB
Scala
34 lines
1.1 KiB
Scala
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/* sbt -- Simple Build Tool
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* Copyright 2010 Mark Harrah
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*/
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package sbt
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import Types._
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// T must be invariant to work properly.
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// Because it is sealed and the only instances go through make,
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// a single AttributeKey instance cannot conform to AttributeKey[T] for different Ts
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sealed trait AttributeKey[T]
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object AttributeKey
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{
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def make[T]: AttributeKey[T] = new AttributeKey[T] {}
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}
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trait AttributeMap
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{
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def apply[T](k: AttributeKey[T]): T
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def get[T](k: AttributeKey[T]): Option[T]
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def contains[T](k: AttributeKey[T]): Boolean
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def put[T](k: AttributeKey[T], value: T): AttributeMap
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}
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object AttributeMap
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{
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def empty: AttributeMap = new BasicAttributeMap(Map.empty)
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}
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private class BasicAttributeMap(backing: Map[AttributeKey[_], Any]) extends AttributeMap
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{
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def apply[T](k: AttributeKey[T]) = backing(k).asInstanceOf[T]
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def get[T](k: AttributeKey[T]) = backing.get(k).asInstanceOf[Option[T]]
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def contains[T](k: AttributeKey[T]) = backing.contains(k)
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def put[T](k: AttributeKey[T], value: T): AttributeMap = new BasicAttributeMap( backing.updated(k, value) )
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}
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