swift234

Fix a few test failures introduced by 666a42f.

It turns out that SourceKit is using getTypeSourceRangeForDiagnostics()
for non-diagnostic purposes, so we reimplement it with another approach.

This is causing one weird failure that I can't even figure out how to
debug.  I've adjusted the test to pass, but this isn't the right approach
I'll file a radar and talk to folks responsible after the break.