closes bpo-34641: Further restrict the LHS of keyword argument function call syntax. (GH-9212)
diff --git a/Doc/whatsnew/3.8.rst b/Doc/whatsnew/3.8.rst
index 259dcf6..b2475c7 100644
--- a/Doc/whatsnew/3.8.rst
+++ b/Doc/whatsnew/3.8.rst
@@ -94,6 +94,10 @@
* Added support of ``\N{name}`` escapes in :mod:`regular expressions <re>`.
(Contributed by Jonathan Eunice and Serhiy Storchaka in :issue:`30688`.)
+* The syntax allowed for keyword names in function calls was further
+ restricted. In particular, ``f((keyword)=arg)`` is no longer allowed. It was
+ never intended to permit more than a bare name on the left-hand side of a
+ keyword argument assignment term. See :issue:`34641`.
New Modules
===========
diff --git a/Lib/test/test_syntax.py b/Lib/test/test_syntax.py
index fa1e7aa..c5b2496 100644
--- a/Lib/test/test_syntax.py
+++ b/Lib/test/test_syntax.py
@@ -269,6 +269,9 @@
>>> f(x.y=1)
Traceback (most recent call last):
SyntaxError: keyword can't be an expression
+>>> f((x)=2)
+Traceback (most recent call last):
+SyntaxError: keyword can't be an expression
More set_context():
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-09-11-23-12-33.bpo-34641.gFBCc9.rst b/Misc/NEWS.d/next/Core and Builtins/2018-09-11-23-12-33.bpo-34641.gFBCc9.rst
new file mode 100644
index 0000000..9b6eb24
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-09-11-23-12-33.bpo-34641.gFBCc9.rst
@@ -0,0 +1,2 @@
+Further restrict the syntax of the left-hand side of keyword arguments in
+function calls. In particular, ``f((keyword)=arg)`` is now disallowed.
diff --git a/Python/ast.c b/Python/ast.c
index 94962e0..b93eb88 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -2815,29 +2815,56 @@
identifier key, tmp;
int k;
- /* chch is test, but must be an identifier? */
- e = ast_for_expr(c, chch);
- if (!e)
- return NULL;
- /* f(lambda x: x[0] = 3) ends up getting parsed with
- * LHS test = lambda x: x[0], and RHS test = 3.
- * SF bug 132313 points out that complaining about a keyword
- * then is very confusing.
- */
- if (e->kind == Lambda_kind) {
+ // To remain LL(1), the grammar accepts any test (basically, any
+ // expression) in the keyword slot of a call site. So, we need
+ // to manually enforce that the keyword is a NAME here.
+ static const int name_tree[] = {
+ test,
+ or_test,
+ and_test,
+ not_test,
+ comparison,
+ expr,
+ xor_expr,
+ and_expr,
+ shift_expr,
+ arith_expr,
+ term,
+ factor,
+ power,
+ atom_expr,
+ atom,
+ 0,
+ };
+ node *expr_node = chch;
+ for (int i = 0; name_tree[i]; i++) {
+ if (TYPE(expr_node) != name_tree[i])
+ break;
+ if (NCH(expr_node) != 1)
+ break;
+ expr_node = CHILD(expr_node, 0);
+ }
+ if (TYPE(expr_node) == lambdef) {
+ // f(lambda x: x[0] = 3) ends up getting parsed with LHS
+ // test = lambda x: x[0], and RHS test = 3. Issue #132313
+ // points out that complaining about a keyword then is very
+ // confusing.
ast_error(c, chch,
"lambda cannot contain assignment");
return NULL;
}
- else if (e->kind != Name_kind) {
+ else if (TYPE(expr_node) != NAME) {
ast_error(c, chch,
- "keyword can't be an expression");
+ "keyword can't be an expression");
return NULL;
}
- else if (forbidden_name(c, e->v.Name.id, ch, 1)) {
+ key = new_identifier(STR(expr_node), c);
+ if (key == NULL) {
return NULL;
}
- key = e->v.Name.id;
+ if (forbidden_name(c, key, chch, 1)) {
+ return NULL;
+ }
for (k = 0; k < nkeywords; k++) {
tmp = ((keyword_ty)asdl_seq_GET(keywords, k))->arg;
if (tmp && !PyUnicode_Compare(tmp, key)) {