File: tcpoly_variance.scala

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scala 2.7.7.dfsg-4
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class A[m[x]] {
 def str: m[Object] = error("foo")
}

class B[m[x]] extends A[m] {
 override def str: m[String]  = error("foo") // since x in m[x] is invariant, ! m[String] <: m[Object]
}