Fixed #7557 -- Added type checking to Variable initialization.

Thanks tobias for the suggestion and boblefrag and saz for work on the
patch.

django/template/base.py

@@ -675,6 +675,9 @@ class Variable(object):
         self.translate = False
         self.message_context = None
 
+        if not isinstance(var, six.string_types):
+            raise TypeError(
+                "Variable must be a string or number, got %s" % type(var))
         try:
             # First try to treat this variable as a number.
             #

tests/template_tests/test_parser.py

@@ -87,6 +87,10 @@ class ParserTests(TestCase):
             Variable, "article._hidden"
         )
 
+        # Variables should raise on non string type
+        with six.assertRaisesRegex(self, TypeError, "Variable must be a string or number, got <(class|type) 'dict'>"):
+            Variable({})
+
     @override_settings(DEBUG=True, TEMPLATE_DEBUG=True)
     def test_compile_filter_error(self):
         # regression test for #19819