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gh-150700: Fix class-scope inline comprehensions when nested scopes reference __class__ and friends (#150735)

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* Fix class-scope inline comprehensions when nested scopes reference `__class__` and friends

In `inline_comprehension()`, when `__class__` / `__classdict__` /
`__conditional_annotations__` appears as `FREE` in a comprehension's
symbol table because a nested scope captured it (e.g. nested lambdas),
this name is still discarded from `comp_free` unconditionally.

This prevents `drop_class_free()` from seeing it, so the appropriate
`ste_needs_(...)` flag is never set on the enclosing class.
That leads to `codegen_make_closure()` throwing `SystemError` when it
couldn't find `__class__` / `__classdict__` /
`__conditional_annotations__` in the class's cellvars.

From now on we just discard from `comp_free` when no child scope
(e.g. a lambda) still needs the name as `FREE`. When a child scope does
need it, keep it in `comp_free` so `drop_class_free()` can set the
appropriate flag and the class creates the implicit cell.

* Fix tests

* Fix typo

* Fix formatting

* Add test checking validity of `__class__` returned

* Prefer 'used' to 'deferred'
This commit is contained in:
Bartosz Sławecki
2026-06-10 00:22:13 +02:00
committed by GitHub
parent 580499177c
commit ce916dc506
3 changed files with 43 additions and 4 deletions
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Python/symtable.c
+9 -4
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@@ -834,17 +834,22 @@ inline_comprehension(PySTEntryObject *ste, PySTEntryObject *comp,
return 0;
}
// __class__, __classdict__ and __conditional_annotations__ are
// never allowed to be free through a class scope (see
// drop_class_free)
// not allowed to be free through a class scope (see
// drop_class_free) unless children scopes need it
if (scope == FREE && ste->ste_type == ClassBlock &&
(_PyUnicode_EqualToASCIIString(k, "__class__") ||
_PyUnicode_EqualToASCIIString(k, "__classdict__") ||
_PyUnicode_EqualToASCIIString(k, "__conditional_annotations__"))) {
scope = GLOBAL_IMPLICIT;
if (PySet_Discard(comp_free, k) < 0) {
int child_needs_free = is_free_in_any_child(comp, k);
if (child_needs_free < 0) {
return 0;
}
if (!child_needs_free) {
if (PySet_Discard(comp_free, k) < 0) {
return 0;
}
}
if (_PyUnicode_EqualToASCIIString(k, "__class__")) {
remove_dunder_class = 1;
}