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[mypyc] Return empty bytes for an empty slice #22335

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Merged
hauntsaninja merged 1 commit into from
Nov 2, 2026
Merged

[mypyc] Return empty bytes for an empty slice #22335

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3 changes: 3 additions & 0 deletions mypyc/lib-rt/bytes_ops.c
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Original file line number Diff line number Diff line change
Expand Up @@ -78,6 +78,9 @@ PyObject *CPyBytes_GetSlice(PyObject *obj, CPyTagged start, CPyTagged end) {
startn = Clamp(startn, 0, len);
endn = Clamp(endn, 0, len);
Py_ssize_t slice_len = endn - startn;
if (slice_len < 0) {
slice_len = 0;
}
if (PyBytes_Check(obj)) {
return PyBytes_FromStringAndSize(PyBytes_AS_STRING(obj) + startn, slice_len);
} else {
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10 changes: 10 additions & 0 deletions mypyc/test-data/run-bytes.test
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Expand Up @@ -243,6 +243,16 @@ def test_endswith() -> None:
assert not test2.endswith(b'other')

[case testBytesSlicing]
from typing import Any, cast

def test_reversed_slice_bounds() -> None:
bounds = (-100, -3, -1, 0, 1, 2, 3, 100, 2**100)
for value in (b"", b"a", b"abc"):
interpreted = cast(Any, value)
for start in bounds:
for end in bounds:
assert value[start:end] == interpreted[start:end]

def test_bytes_slicing() -> None:
b = b'abcdefg'
zero = int()
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