Type alias and higher kinded type cause type mismatch

[olafurpg]

Related #2200.

I found one examples with type aliases and higher kinded types where scalac reports no type errors while dotc reports E007 Type mismatch, see eae920a#commitcomment-21672052

I bumped into this error while trying to compile https://github.com/johnynek/paiges with Dotty. The commands I ran were

$ scalac -version
Scala compiler version 2.12.1 -- Copyright 2002-2016, LAMP/EPFL and Lightbend, Inc.
$ scalac tests/pos/packageobjecttypealias/*.scala
$ ./bin/dotc tests/pos/packageobjecttypealias/*.scala