Fix SF bug #1167751, Argument genexp corner case

Incorrect code was generated for:

  foo(a = i for i in range(10))

This should have generated a SyntaxError.  Fix the Grammar so
it raises a SyntaxError and test it.

I'm uncertain whether this should be backported.  It makes
something that was Syntactically valid invalid.  However,
the code would either be completely broken or do the wrong thing.

Grammar/Grammar

@@ -102,7 +102,7 @@ dictmaker: test ':' test (',' test ':' test)* [',']
 classdef: 'class' NAME ['(' [testlist] ')'] ':' suite
 
 arglist: (argument ',')* (argument [',']| '*' test [',' '**' test] | '**' test)
-argument: [test '='] test [gen_for] # Really [keyword '='] test
+argument: test [gen_for] | test '=' test ['(' gen_for ')']  # Really [keyword '='] test
 
 list_iter: list_for | list_if
 list_for: 'for' exprlist 'in' testlist_safe [list_iter]

Lib/test/test_genexps.py

@@ -82,6 +82,18 @@
        ...
     SyntaxError: invalid syntax
 
+Verify that parenthesis are required when used as a keyword argument value
+
+    >>> dict(a = i for i in xrange(10))
+    Traceback (most recent call last):
+       ...
+    SyntaxError: invalid syntax
+
+Verify that parenthesis are required when used as a keyword argument value
+
+    >>> dict(a = (i for i in xrange(10))) #doctest: +ELLIPSIS
+    {'a': <generator object at ...>}
+
 Verify early binding for the outermost for-expression
 
     >>> x=10
@@ -125,12 +137,12 @@
     >>> (y for y in (1,2)) = 10
     Traceback (most recent call last):
        ...
-    SyntaxError: assignment to generator expression not possible (<doctest test.test_genexps.__test__.doctests[38]>, line 1)
+    SyntaxError: assignment to generator expression not possible (<doctest test.test_genexps.__test__.doctests[40]>, line 1)
 
     >>> (y for y in (1,2)) += 10
     Traceback (most recent call last):
        ...
-    SyntaxError: augmented assignment to generator expression not possible (<doctest test.test_genexps.__test__.doctests[39]>, line 1)
+    SyntaxError: augmented assignment to generator expression not possible (<doctest test.test_genexps.__test__.doctests[41]>, line 1)
 
 
 ########### Tests borrowed from or inspired by test_generators.py ############

Python/graminit.c

@@ -1496,26 +1496,34 @@ static arc arcs_69_0[1] = {
 	{26, 1},
 };
 static arc arcs_69_1[3] = {
-	{25, 2},
+	{147, 2},
-	{147, 3},
+	{25, 3},
 	{0, 1},
 };
 static arc arcs_69_2[1] = {
-	{26, 4},
+	{0, 2},
 };
 static arc arcs_69_3[1] = {
-	{0, 3},
+	{26, 4},
 };
 static arc arcs_69_4[2] = {
-	{147, 3},
+	{13, 5},
 	{0, 4},
 };
-static state states_69[5] = {
+static arc arcs_69_5[1] = {
+	{147, 6},
+};
+static arc arcs_69_6[1] = {
+	{15, 2},
+};
+static state states_69[7] = {
 	{1, arcs_69_0},
 	{3, arcs_69_1},
 	{1, arcs_69_2},
 	{1, arcs_69_3},
 	{2, arcs_69_4},
+	{1, arcs_69_5},
+	{1, arcs_69_6},
 };
 static arc arcs_70_0[2] = {
 	{146, 1},
@@ -1806,7 +1814,7 @@ static dfa dfas[79] = {
 	 "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\002\000"},
 	{324, "arglist", 0, 8, states_68,
 	 "\000\040\010\060\000\000\000\000\000\000\000\000\000\002\000\140\010\111\023\000\000"},
-	{325, "argument", 0, 5, states_69,
+	{325, "argument", 0, 7, states_69,
 	 "\000\040\010\000\000\000\000\000\000\000\000\000\000\002\000\140\010\111\023\000\000"},
 	{326, "list_iter", 0, 2, states_70,
 	 "\000\000\000\000\000\000\000\000\000\000\000\042\000\000\000\000\000\000\000\000\000"},