tpd.ModuleDef fails if owner isn't a class

[DarkDimius]

If one tries to construct such class by hand using tpd.*

class A{
  def p() = {
    object B {val d = 1};
    B.d
  }
}

During creation of object B, Symbol.newModuleSymbol will try to get TermRef(owner.thisType, name), with will obviously lead to prefix being NoPrefix(just like it is in typeCheker generated symbols for such code) which in turn will cause this assertion to fail: https://github.com/lampepfl/dotty/blob/d827b0180b05e7461856f668c3c4ca0ea6ed5d62/src/dotty/tools/dotc/core/Types.scala#L1186

[DarkDimius]

Similar assertion in CachedTypeRef is also broken by this example.
https://github.com/lampepfl/dotty/blob/d827b0180b05e7461856f668c3c4ca0ea6ed5d62/src/dotty/tools/dotc/core/Types.scala#L1192

[odersky]

Fixed in #64