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Scala example source code file (tcpoly_typealias_eta.scala)
The Scala tcpoly_typealias_eta.scala source codetrait A { type m[+x] } trait A2 { type m[+x <: String] } trait A3 { type m[x] } trait FooCov[+x] trait FooCon[-x] trait FooBound[+x <: String] trait BOk1 extends A { type m/*[+x]*/ = FooCov/*[x]*/ } trait BOk2 extends A2 { type m/*[+x <: String]*/ = FooBound/*[x]*/ } trait BOk3 extends A2 { type m/*[+x]*/ = FooCov/*[x]*/ // weaker bound } trait BOk4 extends A3 { type m/*[+x]*/ = FooCov/*[x]*/ // weaker variance } // there are two aspects to check: // does type alias signature (not considering RHS) correspond to abstract type member in super class // does RHS correspond to the type alias sig trait BInv extends A{ type m/*[x]*/ = FooCov/*[x]*/ // error: invariant x in alias def } trait BCon extends A{ type m/*[-x]*/ = FooCon/*[x]*/ // error: contravariant x } trait BBound extends A{ type m/*[+x <: String]*/ = FooBound/*[x]*/ // error: x with stricter bound } Other Scala examples (source code examples)Here is a short list of links related to this Scala tcpoly_typealias_eta.scala source code file: |
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