10000 gh-118513: Fix sibling comprehensions with a name bound in one and gl… · python/cpython@c8deb1e · GitHub
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gh-118513: Fix sibling comprehensions with a name bound in one and global in the other (#118526)
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com> Co-authored-by: Kirill Podoprigora <kirill.bast9@mail.ru>
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-39
lines changed

3 files changed

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‎Lib/test/test_listcomps.py

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Original file line numberDiff line numberDiff line change
@@ -666,6 +666,20 @@ def test_code_replace_extended_arg(self):
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self._check_in_scopes(code, expected)
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self._check_in_scopes(code, expected, exec_func=self._replacing_exec)
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def test_multiple_comprehension_name_reuse(self):
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code = """
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[x for x in [1]]
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y = [x for _ in [1]]
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"""
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self._check_in_scopes(code, {"y": [3]}, ns={"x": 3})
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code = """
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x = 2
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[x for x in [1]]
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y = [x for _ in [1]]
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"""
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self._check_in_scopes(code, {"x": 2, "y": [3]}, ns={"x": 3}, scopes=["class"])
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self._check_in_scopes(code, {"x": 2, "y": [2]}, ns={"x": 3}, scopes=["function", "module"])
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__test__ = {'doctests' : doctests}
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‎Misc/NEWS.d/next/Core and Builtins/2024-05-02-21-19-35.gh-issue-118513.qHODjb.rst

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Fix incorrect :exc:`UnboundLocalError` when two comprehensions in the same function both reference the same name, and in one comprehension the name is bound while in the other it's an implicit global.

‎Python/compile.c

Lines changed: 42 additions & 39 deletions
Original file line numberDiff line numberDiff line change
@@ -5561,10 +5561,48 @@ push_inlined_comprehension_state(struct compiler *c, location loc,
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while (PyDict_Next(entry->ste_symbols, &pos, &k, &v)) {
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assert(PyLong_Check(v));
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long symbol = PyLong_AS_LONG(v);
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// only values bound in the comprehension (DEF_LOCAL) need to be handled
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// at all; DEF_LOCAL | DEF_NONLOCAL can occur in the case of an
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// assignment expression to a nonlocal in the comprehension, these don't
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// need handling here since they shouldn't be isolated
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long scope = (symbol >> SCOPE_OFFSET) & SCOPE_MASK;
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PyObject *outv = PyDict_GetItemWithError(c->u->u_ste->ste_symbols, k);
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if (outv == NULL) {
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if (PyErr_Occurred()) {
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return ERROR;
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}
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outv = _PyLong_GetZero();
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}
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assert(PyLong_CheckExact(outv));
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long outsc = (PyLong_AS_LONG(outv) >> SCOPE_OFFSET) & SCOPE_MASK;
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// If a name has different scope inside than outside the comprehension,
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// we need to temporarily handle it with the right scope while
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// compiling the comprehension. If it's free in the comprehension
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// scope, no special handling; it should be handled the same as the
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// enclosing scope. (If it's free in outer scope and cell in inner
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// scope, we can't treat it as both cell and free in the same function,
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// but treating it as free throughout is fine; it's *_DEREF
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// either way.)
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if ((scope != outsc && scope != FREE && !(scope == CELL && outsc == FREE))
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|| in_class_block) {
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if (state->temp_symbols == NULL) {
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state->temp_symbols = PyDict_New();
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if (state->temp_symbols == NULL) {
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return ERROR;
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}
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}
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// update the symbol to the in-comprehension version and save
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// the outer version; we'll restore it after running the
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// comprehension
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Py_INCREF(outv);
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if (PyDict_SetItem(c->u->u_ste->ste_symbols, k, v) < 0) {
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Py_DECREF(outv);
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return ERROR;
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}
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if (PyDict_SetItem(state->temp_symbols, k, outv) < 0) {
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Py_DECREF(outv);
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return ERROR;
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}
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Py_DECREF(outv);
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}
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// locals handling for names bound in comprehension (DEF_LOCAL |
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// DEF_NONLOCAL occurs in assignment expression to nonlocal)
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if ((symbol & DEF_LOCAL && !(symbol & DEF_NONLOCAL)) || in_class_block) {
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if (!_PyST_IsFunctionLike(c->u->u_ste)) {
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// non-function scope: override this name to use fast locals
@@ -5589,41 +5627,6 @@ push_inlined_comprehension_state(struct compiler *c, location loc,
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}
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}
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}
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long scope = (symbol >> SCOPE_OFFSET) & SCOPE_MASK;
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PyObject *outv = PyDict_GetItemWithError(c->u->u_ste->ste_symbols, k);
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if (outv == NULL) {
5595-
outv = _PyLong_GetZero();
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}
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assert(PyLong_Check(outv));
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long outsc = (PyLong_AS_LONG(outv) >> SCOPE_OFFSET) & SCOPE_MASK;
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if (scope != outsc && !(scope == CELL && outsc == FREE)) {
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// If a name has different scope inside than outside the
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// comprehension, we need to temporarily handle it with the
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// right scope while compiling the comprehension. (If it's free
5603-
// in outer scope and cell in inner scope, we can't treat it as
5604-
// both cell and free in the same function, but treating it as
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// free throughout is fine; it's *_DEREF either way.)
5606-
5607-
if (state->temp_symbols == NULL) {
5608-
state->temp_symbols = PyDict_New();
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if (state->temp_symbols == NULL) {
5610-
return ERROR;
5611-
}
5612-
}
5613-
// update the symbol to the in-comprehension version and save
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// the outer version; we'll restore it after running the
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// comprehension
5616-
Py_INCREF(outv);
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if (PyDict_SetItem(c->u->u_ste->ste_symbols, k, v) < 0) {
5618< 341A /code>-
Py_DECREF(outv);
5619-
return ERROR;
5620-
}
5621-
if (PyDict_SetItem(state->temp_symbols, k, outv) < 0) {
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Py_DECREF(outv);
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return ERROR;
5624-
}
5625-
Py_DECREF(outv);
5626-
}
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// local names bound in comprehension must be isolated from
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// outer scope; push existing value (which may be NULL if
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// not defined) on stack

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