Fix ExplicitSelf phase
Fix ExplicitSelf phase

After inlining we got a Ycheck error of the form:

found   : `this.asInstanceOf[SelfType].C`
expected: `this.C`

The fact that it was related inlining was coincidental I think.
We fix the problem by expanding to

     this.asInstanceOf[SelfType & this.type].C

instead.

som-snytt/dotty,lampepfl/dotty,dotty-staging/dotty,dotty-staging/dotty,som-snytt/dotty,lampepfl/dotty,dotty-staging/dotty,dotty-staging/dotty,dotty-staging/dotty,sjrd/dotty,sjrd/dotty,lampepfl/dotty,sjrd/dotty,sjrd/dotty,som-snytt/dotty,sjrd/dotty,lampepfl/dotty,som-snytt/dotty,lampepfl/dotty,som-snytt/dotty