Fix/#329 and others

[odersky]

Fix of #329 and SI 3252. Review by @olhotak.

[olhotak]

The last two commits fixing #329 LGTM.

[retronym]

I notice that matchingParams differs from Scalac in that it no longer equates a Java defined Object with a Scala defined Any.

% tail sandbox/{A.java,B.scala}
==> sandbox/A.java <==
public interface A {
    void o(Object o);
}

==> sandbox/B.scala <==
trait T { def t(o: Object): Unit }

class B extends A with T {
  override def o(o: Any): Unit = ()

  override def t(o: AnyRef): Unit = ()
}

% scalac-hash v2.11.5 sandbox/{A.java,B.scala}

% ../dotty/bin/dotc sandbox/{A.java,B.scala}
sandbox/B.scala:4: error: method o overrides nothing
  override def o(o: Any): Unit = ()
                 ^
one error found

See scala/scala@e2fd411 / scala/scala@e572f29 for the history.

[retronym]

Although I wasn't able to exploit it, I wonder if underlyingIfRepeated could ever spuriously associate signatures like def foo(s: Seq[Any]) and def foo(a: Any*). A comment to explain why this isn't the case would be welcome in the code.

UPDATE Actually, I found a way to break it:

% cat sandbox/test.scala
trait T {
  def t(a: Any*) = 0
}
class C extends T {
  override def t(a: Seq[Any]) = 0
}

% ~/code/scala scalac-hash v2.11.5 sandbox/test.scala
sandbox/test.scala:5: error: method t overrides nothing.
Note: the super classes of class C contain the following, non final members named t:
def t(a: Any*): Int
  override def t(a: Seq[Any]) = 0
               ^
one error found

% (cd ../dotty; git log --oneline -1)
eeee941 More negative override tests

% ../dotty/bin/dotc sandbox/test.scala

[odersky]

@retronym I added the failing Java/Scala override as a test.

Regarding underlyingIfRepeated, I'll revert that one.

[odersky]

Rebased to current master

[odersky]

I am going to merge now since reviewers comments are taken care of and there are other PRs based on this one.