swift234

SILGen: Implement variable bindings.

As clause matrix specialization exposes columns with variable bindings, bind all of the variables in each column to a new box for the variables in that column. (Since only one row out of the matrix ever ends up getting executed, we can share one box for the entire column.) Set up a scope hierarchy following that of the specialized clause matrices, and associate each case with the scope it needs to see all the variables of its fully-destructured pattern clause. Remove our ad-hoc hack for binding ExprPattern implicit variables, and bind them to the column's box too.

Swift SVN r6127