swift234

change PreCheckExpression to keep track of the current DeclContext when it is
recursing down through ClosureExprs.  This makes sure that it performs name
lookups with the right context.  Add some assertions to make sure that it is
getting the right thing.

This exposed that PatternBinding initializer lookups were passing the wrong
declcontext: the context of the PBD, not the initializer itself.  Fixing this
allows us to correctly reject some cases that passed through before.


Swift SVN r14670