Fix support comprehensions inside functions when use strict_undefined…

… flag

Fixes: #398

The element or key and value used respectively in list/set comprehension
and dictionary comprehension cannot be used to declare identifiers so no
need to visit them.

mako/pyparser.py

@@ -92,8 +92,6 @@ def visit_FunctionDef(self, node):
 
     def visit_ListComp(self, node):
         if self.in_function:
-            if not isinstance(node.elt, _ast.Name):
-                self.visit(node.elt)
             for comp in node.generators:
                 self.visit(comp.iter)
         else:
@@ -103,8 +101,6 @@ def visit_ListComp(self, node):
 
     def visit_DictComp(self, node):
         if self.in_function:
-            if not isinstance(node.key, _ast.Name):
-                self.visit(node.elt)
             for comp in node.generators:
                 self.visit(comp.iter)
         else:

test/test_template.py

@@ -878,6 +878,21 @@ def test_list_comprehensions_plus_undeclared_strict(self):
 
         eq_(result_lines(t.render(t="T")), ["t is: T", "a,b,c"])
 
+    def test_dict_comprehensions_in_function_plus_undeclared_strict(self):
+        t = Template(
+            """
+<%
+    def foo():
+        return {s[0]: s for s in ('foo',)}
+%>
+
+${ foo()['f'] }
+""",
+            strict_undefined=True,
+        )
+
+        eq_(result_lines(t.render()), ["foo"])
+
 
 class StopRenderingTest(TemplateTest):
     def test_return_in_template(self):