swift234

SILGenPattern: Handle subsumption and orthogonality of superclasses in 'is' patterns.

Now that we can ask about superclasses outside of the type-checker, we can consider superclass relationships when pattern-matching 'is' patterns, producing better decision trees when a subclass checked is subsumed by a superclass check, a subclass check renders a superclass check redundant, or two classes or orthogonal and a check of one rules out the other.

Swift SVN r8769