JS: Fix missing flow into rest pattern lvalue

Author: asgerf

javascript/ql/lib/semmle/javascript/dataflow/DataFlow.qll

@@ -1610,6 +1610,11 @@ module DataFlow {
       pred = TElementPatternNode(_, element) and
       succ = lvalueNodeInternal(element)
     )
+    or
+    exists(Expr rest |
+      pred = TRestPatternNode(_, rest) and
+      succ = lvalueNodeInternal(rest)
+    )
   }
 
   /**

javascript/ql/test/library-tests/GetALocalSource/rest-pattern.js

@@ -1,15 +1,15 @@
 function t1() {
     const { ...rest } = source('t1.1');
-    rest; // $ MISSING: getALocalSource=rest
+    rest; // $ getALocalSource=rest
 }
 
 function t2() {
     const [ ...rest ] = source('t2.1');
-    rest; // $ MISSING: getALocalSource=rest
+    rest; // $ getALocalSource=rest
 }
 
 function t3() {
     const { p1, ...rest } = source('t3.1');
     p1; // $ getALocalSource=p1
-    rest; // $ MISSING: getALocalSource=rest
+    rest; // $ getALocalSource=rest
 }

javascript/ql/test/library-tests/GetALocalSource/test.expected

@@ -1 +1,4 @@
+| rest-pattern.js:3:5:3:8 | rest | rest |
+| rest-pattern.js:8:5:8:8 | rest | rest |
 | rest-pattern.js:13:5:13:6 | p1 | p1 |
+| rest-pattern.js:14:5:14:8 | rest | rest |