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Diffstat (limited to 'test/files/run/t7899-regression.scala')
-rw-r--r-- | test/files/run/t7899-regression.scala | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/test/files/run/t7899-regression.scala b/test/files/run/t7899-regression.scala new file mode 100644 index 0000000000..67d38cdd1d --- /dev/null +++ b/test/files/run/t7899-regression.scala @@ -0,0 +1,24 @@ +import language.higherKinds + +object Test { + trait Monad[M[_]] { + def foo[A](ma: M[A])(f: M[A] => Any) = f(ma) + } + implicit def function1Covariant[T]: Monad[({type l[a] = (T => a)})#l] = + new Monad[({type l[a] = (T => a)})#l] {} + + def main(args: Array[String]) { + // inference of T = (=> Any) here was outlawed by SI-7899 / 8ed7099 + // but this pattern is used in Scalaz in just a few places and caused + // a regression. + // + // Inference of a by-name type doesn't *always* lead to a ClassCastException, + // it only gets there if a method in generic code accepts a parameter of + // that type. + // + // We need to introduce the stricter inference rules gradually, probably + // with a warning. + val m = implicitly[Monad[({type f[+x] = (=> Any) => x})#f]] + assert(m.foo[Int]((x => 0))(f => f(???)) == 0) + } +} |