Scala: Implicit parameter resolution precedence

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I wrote my own answer in the form of a blog post revisiting implicits without import tax.

Update: Furthermore, the comments from Martin Odersky in the above post revealed that the Scala 2.9.1’s behavior of LocalIntFoo winning over ImportedIntFoo is in fact a bug. See implicit parameter precedence again.

  • 1) implicits visible to current invocation scope via local declaration, imports, outer scope, inheritance, package object that are accessible without prefix.
  • 2) implicit scope, which contains all sort of companion objects and package object that bear some relation to the implicit’s type which we search for (i.e. package object of the type, companion object of the type itself, of its type constructor if any, of its parameters if any, and also of its supertype and supertraits).

If at either stage we find more than one implicit, static overloading rule is used to resolve it.

Update 2: When I asked Josh about Implicits without Import Tax, he explained to me that he was referring to name binding rules for implicits that are named exactly the same.

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