Fix bug in erasedLub leading to incorrect signatures

[smarter]

Before this commit, the added testcase failed in a strange way:

14 |  def bla(foo: Foo) = orElse2(identity).apply(foo)
   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |value of type <nonsensical><notype></nonsensical> does not take parameters

This happened because the TermRef for the apply method had an incorrect
signature (with a result type of Object instead of Foo), therefore its underlying type was NoType.

According to the documentation of erasedLub, the erasure should be:

a common superclass or trait S of the argument classes, with the
following two properties:

• S is minimal: no other common superclass or trait derives from S]
• S is last : in the linearization of the first argument type tp1
  there are no minimal common superclasses or traits that
  come after S.
  (the reason to pick last is that we prefer classes over traits that way).

I'm not convinced that the implementation satisfies either of these two
properties, but this commit at least makes S closer to being minimal by
making sure that it does not derive from the last seen best candidate never derives from it.

[odersky]

The change LGTM. In the comment leading up to it, there's a stray ]. Also, we should change lub to erased lub in that comment for clarity.

[odersky]

I'll merge and piggyback the comment on some future PR.

[smarter]

Ok, I think we should also take a closer look to make sure the comment matches the implementation.

…

On Mar 9, 2017 14:08, "odersky" ***@***.***> wrote: Merged #2070 <#2070>. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#2070 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAD3xgerMRdMzUeTxLKs-BiskyiI0vROks5rj_nIgaJpZM4MXXAl> .