swift234

testcase for QoI of the new 'if let' model:
 - Rewrite "if let x? = foo()" to "if let x = foo()"
 - Rewrite "if let <complex refutable pattern> = foo()" to "if case let"
 - Handle "if let case" just as well as "if case let" and fixit it to the correct form.



Swift SVN r27960