JS: Fix bad join order in getNextToken()

Author: asgerf

javascript/ql/lib/semmle/javascript/Tokens.qll

@@ -4,6 +4,14 @@
 
 import javascript
 
+overlay[local]
+private predicate adjacentTokens(@token token1, @token token2) {
+  exists(@toplevel top, int index |
+    tokeninfo(token1, _, top, index, _) and
+    tokeninfo(token2, _, top, index + 1, _)
+  )
+}
+
 /**
  * A token occurring in a piece of JavaScript source code.
  *
@@ -27,10 +35,7 @@ class Token extends Locatable, @token {
   string getValue() { tokeninfo(this, _, _, _, result) }
 
   /** Gets the token following this token inside the same toplevel structure, if any. */
-  Token getNextToken() {
-    this.getTopLevel() = result.getTopLevel() and
-    this.getIndex() + 1 = result.getIndex()
-  }
+  Token getNextToken() { adjacentTokens(this, result) }
 
   /** Gets the token preceding this token inside the same toplevel structure, if any. */
   Token getPreviousToken() { result.getNextToken() = this }