Python: Update type-tracking snippet

based on what I learned in #5184

Author: RasmusWL

python/.vscode/ql.code-snippets

@@ -105,8 +105,8 @@
         "scope": "ql",
         "prefix": "type tracking",
         "body": [
-            "/** Gets a reference to a ${3:thing}. */",
-            "private DataFlow::Node ${1:myType}(DataFlow::TypeTracker t) {",
+            "/** Gets a reference to ${3:a thing}. */",
+            "private DataFlow::LocalSourceNode ${1:myType}(DataFlow::TypeTracker t) {",
             "  t.start() and",
             "  result = ${2:value}",
             "  or",
@@ -115,9 +115,9 @@
             "  )",
             "}",
             "",
-            "/** Gets a reference to a ${3:thing}. */",
+            "/** Gets a reference to $3. */",
             "DataFlow::Node $1() {",
-            "  result = $1(DataFlow::TypeTracker::end())",
+            "  $1(DataFlow::TypeTracker::end()).flowsTo(result)",
             "}"
         ],
         "description": "Type tracking predicate",

python/ql/src/semmle/python/dataflow/new/TypeTracker.qll

@@ -180,7 +180,7 @@ private newtype TTypeTracker = MkTypeTracker(Boolean hasCall, OptionalAttributeN
  * It is recommended that all uses of this type are written in the following form,
  * for tracking some type `myType`:
  * ```
- * DataFlow::Node myType(DataFlow::TypeTracker t) {
+ * DataFlow::LocalSourceNode myType(DataFlow::TypeTracker t) {
  *   t.start() and
  *   result = < source of myType >
  *   or
@@ -189,7 +189,7 @@ private newtype TTypeTracker = MkTypeTracker(Boolean hasCall, OptionalAttributeN
  *   )
  * }
  *
- * DataFlow::Node myType() { result = myType(DataFlow::TypeTracker::end()) }
+ * DataFlow::Node myType() { myType(DataFlow::TypeTracker::end()).flowsTo(result) }
  * ```
  *
  * Instead of `result = myType(t2).track(t2, t)`, you can also use the equivalent