refactor isInterpretedAsRegExp to directly work on a DataFlow node

Author: erik-krogh

javascript/ql/src/semmle/javascript/Regexp.qll

@@ -818,23 +818,23 @@ predicate isInterpretedAsRegExp(DataFlow::Node source) {
     source = DataFlow::globalVarRef("RegExp").getAnInvocation().getArgument(0)
     or
     // The argument of a call that coerces the argument to a regular expression.
-    exists(MethodCallExpr mce, string methodName |
+    exists(DataFlow::MethodCallNode mce, string methodName |
       mce.getReceiver().analyze().getAType() = TTString() and
       mce.getMethodName() = methodName and
       not exists(Function func |
-        func = any(DataFlow::MethodCallNode call | call.getEnclosingExpr() = mce).getACallee()
+        func = mce.getACallee()
       |
         not isNativeStringMethod(func, methodName)
       )
     |
-      methodName = "match" and source.asExpr() = mce.getArgument(0) and mce.getNumArgument() = 1
+      methodName = "match" and source = mce.getArgument(0) and mce.getNumArgument() = 1
       or
       methodName = "search" and
-      source.asExpr() = mce.getArgument(0) and
+      source = mce.getArgument(0) and
       mce.getNumArgument() = 1 and
       // "search" is a common method name, and so we exclude chained accesses
       // because `String.prototype.search` returns a number
-      not exists(PropAccess p | p.getBase() = mce)
+      not exists(PropAccess p | p.getBase() = mce.getEnclosingExpr())
     )
   )
 }