Add VariableType test for unnamed variables

Author: fwcd

test/SourceKit/VariableType/unnamed.swift

@@ -0,0 +1,10 @@
+let = 2
+let : Int = 4
+
+let x: (String) -> Void = { (: String) in }
+
+// RUN: %sourcekitd-test -req=collect-var-type %s -- %s | %FileCheck %s
+// CHECK: <VariableTypes>
+// CHECK-NEXT: (4:5, 4:6): (String) -> Void (explicit type: 1)
+// CHECK-NEXT: </VariableTypes>
+