Turn MenuNode/Symbol/Choice.referenced() into a @Property

Having it as a function is inconsistent, since all other read-only
fields use properties. Oversight.

Major version will be bumped to 7, though the function version wasn't in
for long.

kconfiglib.py

@@ -2913,6 +2913,13 @@ class Symbol(object):
       parent dependencies are automatically propagated to the conditions of
       properties, so normally it's redundant to check the direct dependencies.
 
+    referenced:
+      A set() with all symbols and choices referenced in the properties and
+      property conditions of the symbol.
+
+      Also includes dependencies inherited from surrounding menus and if's.
+      Choices appear in the dependencies of choice symbols.
+
     env_var:
       If the Symbol has an 'option env="FOO"' option, this contains the name
       ("FOO") of the environment variable. None for symbols without no
@@ -3334,17 +3341,14 @@ def unset_value(self):
             self.user_value = None
             self._rec_invalidate_if_has_prompt()
 
+    @property
     def referenced(self):
         """
-        Returns a set() of all symbols and choices referenced in the properties
-        and property conditions of the symbol.
-
-        Also includes dependencies inherited from surrounding menus and if's.
-        Choices appear in the dependencies of choice symbols.
+        See the class documentation.
         """
         res = set()
         for node in self.nodes:
-            res |= node.referenced()
+            res |= node.referenced
 
         return res
 
@@ -3776,6 +3780,12 @@ class Choice(object):
     direct_dep:
       See Symbol.direct_dep.
 
+    referenced:
+      A set() with all symbols referenced in the properties and property
+      conditions of the choice.
+
+      Also includes dependencies inherited from surrounding menus and if's.
+
     is_optional:
       True if the choice has the 'optional' flag set on it and can be in
       n mode.
@@ -3925,17 +3935,14 @@ def unset_value(self):
             self.user_value = self.user_selection = None
             self._rec_invalidate()
 
+    @property
     def referenced(self):
         """
-        Returns a set() of all symbols and choices referenced in the properties
-        and property conditions of the choice.
-
-        Also includes dependencies inherited from surrounding menus and if's.
-        Choices appear in the dependencies of choice symbols.
+        See the class documentation.
         """
         res = set()
         for node in self.nodes:
-            res |= node.referenced()
+            res |= node.referenced
 
         return res
 
@@ -4175,6 +4182,13 @@ class MenuNode(object):
       'visible if' dependencies are recursively propagated to the prompts of
       symbols and choices within the menu.
 
+    referenced:
+      A set() with all symbols and choices referenced in the properties and
+      property conditions of the menu node.
+
+      Also includes dependencies inherited from surrounding menus and if's.
+      Choices appear in the dependencies of choice symbols.
+
     is_menuconfig:
       Set to True if the children of the menu node should be displayed in a
       separate menu. This is the case for the following items:
@@ -4226,13 +4240,10 @@ def __init__(self):
         self.implies = []
         self.ranges = []
 
+    @property
     def referenced(self):
         """
-        Returns a set() of all symbols and choices referenced in the properties
-        and property conditions of the menu node.
-
-        Also includes dependencies inherited from surrounding menus and if's.
-        Choices appear in the dependencies of choice symbols.
+        See the class documentation.
         """
         # self.dep is included to catch dependencies from a lone 'depends on'
         # when there are no properties to propagate it to

testsuite.py

@@ -1009,12 +1009,12 @@ def verify_expr_items(expr, *sym_names):
     )
 
 
-    print("Testing MenuNode/Symbol/Choice.referenced()")
+    print("Testing MenuNode/Symbol/Choice.referenced")
 
     c = Kconfig("Kconfiglib/tests/Kreferenced", warn=False)
 
     def verify_deps(item, *dep_names):
-        verify_equal(tuple(sorted(item.name for item in item.referenced())),
+        verify_equal(tuple(sorted(item.name for item in item.referenced)),
                      dep_names)
 
     verify_deps(c.top_node, "y")