Bug #1385040: don't allow "def foo(a=1, b): pass" in the compiler package.

Lib/compiler/transformer.py

@@ -841,17 +841,15 @@ class Transformer:
             names.append(self.com_fpdef(node))
 
             i = i + 1
-            if i >= len(nodelist):
-                break
-
-            if nodelist[i][0] == token.EQUAL:
+            if i < len(nodelist) and nodelist[i][0] == token.EQUAL:
                 defaults.append(self.com_node(nodelist[i + 1]))
                 i = i + 2
             elif len(defaults):
-                # XXX This should be a syntax error.
-                # Treat "(a=1, b)" as "(a=1, b=None)"
-                defaults.append(Const(None))
+                # we have already seen an argument with default, but here
+                # came one without
+                raise SyntaxError, "non-default argument follows default argument"
 
+            # skip the comma
             i = i + 1
 
         return names, defaults, flags

Lib/test/test_compiler.py

@@ -56,6 +56,9 @@ class CompilerTest(unittest.TestCase):
     def testYieldExpr(self):
         compiler.compile("def g(): yield\n\n", "<string>", "exec")
 
+    def testDefaultArgs(self):
+        self.assertRaises(SyntaxError, compiler.parse, "def foo(a=1, b): pass")
+
     def testLineNo(self):
         # Test that all nodes except Module have a correct lineno attribute.
         filename = __file__

Misc/NEWS

@@ -91,6 +91,9 @@ Extension Modules
 Library
 -------
 
+- Bug #1385040: don't allow "def foo(a=1, b): pass" in the compiler
+  package.
+
 - Patch #1472854: make the rlcompleter.Completer class usable on non-
   UNIX platforms.