prevent lambda functions from having docstrings #8164

Lib/test/test_compile.py

@@ -353,6 +353,10 @@ if 1:
         f1, f2 = f()
         self.assertNotEqual(id(f1.func_code), id(f2.func_code))
 
+    def test_lambda_doc(self):
+        l = lambda: "foo"
+        self.assertIsNone(l.__doc__)
+
     def test_unicode_encoding(self):
         code = u"# -*- coding: utf-8 -*-\npass\n"
         self.assertRaises(SyntaxError, compile, code, "tmp", "exec")

Misc/NEWS

@@ -12,6 +12,8 @@ What's New in Python 2.7 beta 1?
 Core and Builtins
 -----------------
 
+- Issue #8164: Don't allow lambda functions to have a docstring.
+
 - Issue #3137: Don't ignore errors at startup, especially a keyboard interrupt
   (SIGINT).  If an error occurs while importing the site module, the error is
   printed and Python exits.  Initialize the GIL before importing the site

Python/compile.c

@@ -1519,6 +1519,11 @@ compiler_lambda(struct compiler *c, expr_ty e)
 	/* unpack nested arguments */
 	compiler_arguments(c, args);
 
+	/* Make None the first constant, so the lambda can't have a
+	   docstring. */
+	if (compiler_add_o(c, c->u->u_consts, Py_None) < 0)
+		return 0;
+	
 	c->u->u_argcount = asdl_seq_LEN(args->args);
 	VISIT_IN_SCOPE(c, expr, e->v.Lambda.body);
 	if (c->u->u_ste->ste_generator) {