This test covers the special case of renaming a type switch var.

-- p.go --
package p

func _(x interface{}) {
	switch y := x.(type) { //@rename("y", "z", yToZ)
	case string:
		print(y) //@rename("y", "z", yToZ)
	default:
		print(y) //@rename("y", "z", yToZ)
	}
}

-- @yToZ/p.go --
@@ -4 +4 @@
-	switch y := x.(type) { //@rename("y", "z", yToZ)
+	switch z := x.(type) { //@rename("y", "z", yToZ)
@@ -6 +6 @@
-		print(y) //@rename("y", "z", yToZ)
+		print(z) //@rename("y", "z", yToZ)
@@ -8 +8 @@
-		print(y) //@rename("y", "z", yToZ)
+		print(z) //@rename("y", "z", yToZ)