Fix rest parameters with flow type casting (#4636)

Do not skip TypeCastExpressions when finding referenced identifiers as the
type cast contains valid non flow code that we need to visit.

packages/babel-plugin-transform-es2015-parameters/src/rest.js

@@ -30,6 +30,8 @@ let memberExpressionOptimisationVisitor = {
   },
 
   Flow(path) {
+    // Do not skip TypeCastExpressions as the contain valid non flow code
+    if (path.isTypeCastExpression()) return;
     // don't touch reference in type annotations
     path.skip();
   },