the Slice in x[::] has to have step as None to help the interpreter

This commit is contained in:
Benjamin Peterson 2009-07-20 20:28:08 +00:00
parent a2514f4ce9
commit 4879c907ce
3 changed files with 17 additions and 5 deletions

View file

@ -1471,7 +1471,21 @@ ast_for_slice(struct compiling *c, const node *n)
ch = CHILD(n, NCH(n) - 1);
if (TYPE(ch) == sliceop) {
if (NCH(ch) != 1) {
if (NCH(ch) == 1) {
/*
This is an extended slice (ie "x[::]") with no expression in the
step field. We set this literally to "None" in order to
disambiguate it from x[:]. (The interpreter might have to call
__getslice__ for x[:], but it must call __getitem__ for x[::].)
*/
identifier none = new_identifier("None", c->c_arena);
if (!none)
return NULL;
ch = CHILD(ch, 0);
step = Name(none, Load, LINENO(ch), ch->n_col_offset, c->c_arena);
if (!step)
return NULL;
} else {
ch = CHILD(ch, 1);
if (TYPE(ch) == test) {
step = ast_for_expr(c, ch);