swift234

Improve var decl completion in switch cases

Variables bound in the case item pattern should be available inside the
case body and in the where clause, but not elsewhere within the
statement (e.g. other case items). The added accessor
CaseStmt.getLabelItemsRange() is needed to be able to determine the
difference between a completion location after a colon and one where
the colon doesn’t exist (in both cases this would be in the — implicit
— body statement range).