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gh-130821: Add type information to wrong type error messages #130835

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gh-130821: Add type information to wrong type error messages #130835

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a513ee8
Add type information to wrong type error messages
donBarbos Mar 4, 2025
4d792e4
Use %T to format type names
donBarbos Mar 5, 2025
d976676
Fix error message for methods return type
donBarbos Apr 28, 2025
d811b4c
Revert "Fix error message for methods return type"
donBarbos Apr 28, 2025
70d57c2
Use new message template
donBarbos Apr 28, 2025
b6f75e4
Merge branch 'main' into issue-130821
donBarbos Apr 28, 2025
390f941
Improve message and fix test
donBarbos Apr 28, 2025
d2e54e6
Fix more methods
donBarbos Apr 28, 2025
0ac8a1c
Escape parentheses in regex pattern to fix test match
donBarbos Apr 28, 2025
59bca2d
Fix message for coroutine test
donBarbos Apr 28, 2025
51a6c79
Add News entry
donBarbos Apr 28, 2025
699b112
Update message template
donBarbos Apr 28, 2025
06606e4
Merge branch 'main' into issue-130821
donBarbos May 6, 2025
8c142f3
Merge branch 'main' into issue-130821
serhiy-storchaka Jul 6, 2025
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51 changes: 25 additions & 26 deletions Objects/abstract.c
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Original file line number Diff line number Diff line change
Expand Up @@ -129,8 +129,9 @@ PyObject_LengthHint(PyObject *o, Py_ssize_t defaultvalue)
return defaultvalue;
}
if (!PyLong_Check(result)) {
PyErr_Format(PyExc_TypeError, "__length_hint__ must be an integer, not %.100s",
Py_TYPE(result)->tp_name);
PyErr_Format(PyExc_TypeError,
"%T.__length_hint__ must return type int (not %T)",
o, result);
Py_DECREF(result);
return -1;
}
Expand All @@ -140,7 +141,9 @@ PyObject_LengthHint(PyObject *o, Py_ssize_t defaultvalue)
return -1;
}
if (res < 0) {
PyErr_Format(PyExc_ValueError, "__length_hint__() should return >= 0");
PyErr_Format(PyExc_ValueError,
"%T.__length_hint__ must return positive int (not %T)",
o, result);
return -1;
}
return res;
Expand Down Expand Up @@ -884,8 +887,8 @@ PyObject_Format(PyObject *obj, PyObject *format_spec)

if (result && !PyUnicode_Check(result)) {
PyErr_Format(PyExc_TypeError,
"__format__ must return a str, not %.200s",
Py_TYPE(result)->tp_name);
"%T.__format__ must return type str (not %T)",
obj, result);
Py_SETREF(result, NULL);
goto done;
}
Expand Down Expand Up @@ -1418,17 +1421,17 @@ _PyNumber_Index(PyObject *item)

if (!PyLong_Check(result)) {
PyErr_Format(PyExc_TypeError,
"__index__ returned non-int (type %.200s)",
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I don't see much reason to change this error message either.

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@donBarbos donBarbos Apr 29, 2025 •
edited
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I changed it to the more common way as you recommended elsewhere: __method__() must return an int, not ...
and added type info before method name, like for other methods

Py_TYPE(result)->tp_name);
"%T.__index__ must return type int (not %T)",
item, result);
Py_DECREF(result);
return NULL;
}
/* Issue #17576: warn if 'result' not of exact type int. */
if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
"__index__ returned non-int (type %.200s). "
"%T.__index__ must return type int (not %T). "
"The ability to return an instance of a strict subclass of int "
"is deprecated, and may be removed in a future version of Python.",
Py_TYPE(result)->tp_name)) {
item, result)) {
Py_DECREF(result);
return NULL;
}
Expand Down Expand Up @@ -1528,17 +1531,16 @@ PyNumber_Long(PyObject *o)

if (!PyLong_Check(result)) {
PyErr_Format(PyExc_TypeError,
"__int__ returned non-int (type %.200s)",
Py_TYPE(result)->tp_name);
"%T.__int__ must return type int (not %T)", o, result);
Py_DECREF(result);
return NULL;
}
/* Issue #17576: warn if 'result' not of exact type int. */
if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
"__int__ returned non-int (type %.200s). "
"%T.__int__ must return type int (not %T). "
"The ability to return an instance of a strict subclass of int "
"is deprecated, and may be removed in a future version of Python.",
Py_TYPE(result)->tp_name)) {
o, result)) {
Py_DECREF(result);
return NULL;
}
Expand Down Expand Up @@ -1606,17 +1608,17 @@ PyNumber_Float(PyObject *o)

if (!PyFloat_Check(res)) {
PyErr_Format(PyExc_TypeError,
"%.50s.__float__ returned non-float (type %.50s)",
Py_TYPE(o)->tp_name, Py_TYPE(res)->tp_name);
"%T.__float__ must return type float (not %T)",
o, res);
Py_DECREF(res);
return NULL;
}
/* Issue #26983: warn if 'res' not of exact type float. */
if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
"%.50s.__float__ returned non-float (type %.50s). "
"%T.__float__ must return type float (not %T). "
"The ability to return an instance of a strict subclass of float "
"is deprecated, and may be removed in a future version of Python.",
Py_TYPE(o)->tp_name, Py_TYPE(res)->tp_name)) {
o, res)) {
Py_DECREF(res);
return NULL;
}
Expand Down Expand Up @@ -2432,10 +2434,8 @@ method_output_as_list(PyObject *o, PyObject *meth)
PyThreadState *tstate = _PyThreadState_GET();
if (_PyErr_ExceptionMatches(tstate, PyExc_TypeError)) {
_PyErr_Format(tstate, PyExc_TypeError,
"%.200s.%U() returned a non-iterable (type %.200s)",
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Here I strongly prefer the old message. Iterable is not a type, it's a category of types.

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what do you think about new message: "%T.%U() must return an iterable, not %T"

Py_TYPE(o)->tp_name,
meth,
Py_TYPE(meth_output)->tp_name);
"%T.%U() must return type iterable (not %T)",
o, meth, meth_output);
}
Py_DECREF(meth_output);
return NULL;
Expand Down Expand Up @@ -2815,9 +2815,8 @@ PyObject_GetIter(PyObject *o)
PyObject *res = (*f)(o);
if (res != NULL && !PyIter_Check(res)) {
PyErr_Format(PyExc_TypeError,
"iter() returned non-iterator "
"of type '%.100s'",
Py_TYPE(res)->tp_name);
"%T.iter() must return type iterator of type '%T'",
o, res);
Py_SETREF(res, NULL);
}
return res;
Expand All @@ -2836,8 +2835,8 @@ PyObject_GetAIter(PyObject *o) {
PyObject *it = (*f)(o);
if (it != NULL && !PyAIter_Check(it)) {
PyErr_Format(PyExc_TypeError,
"aiter() returned not an async iterator of type '%.100s'",
Py_TYPE(it)->tp_name);
"%T.aiter() must return type async iterator of type '%T'",
o, it);
Py_SETREF(it, NULL);
}
return it;
Expand Down
8 changes: 4 additions & 4 deletions Objects/bytesobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -567,8 +567,8 @@ format_obj(PyObject *v, const char **pbuf, Py_ssize_t *plen)
return NULL;
if (!PyBytes_Check(result)) {
PyErr_Format(PyExc_TypeError,
"__bytes__ returned non-bytes (type %.200s)",
Py_TYPE(result)->tp_name);
"%T.__bytes__ must return type bytes (not %T)",
v, result);
Py_DECREF(result);
return NULL;
}
Expand Down Expand Up @@ -2762,8 +2762,8 @@ bytes_new_impl(PyTypeObject *type, PyObject *x, const char *encoding,
return NULL;
if (!PyBytes_Check(bytes)) {
PyErr_Format(PyExc_TypeError,
"__bytes__ returned non-bytes (type %.200s)",
Py_TYPE(bytes)->tp_name);
"%T.__bytes__ must return type bytes (not %T)",
x, bytes);
Py_DECREF(bytes);
return NULL;
}
Expand Down
8 changes: 4 additions & 4 deletions Objects/complexobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -499,17 +499,17 @@ try_complex_special_method(PyObject *op)
}
if (!PyComplex_Check(res)) {
PyErr_Format(PyExc_TypeError,
"__complex__ returned non-complex (type %.200s)",
Py_TYPE(res)->tp_name);
"%T.__complex__ must return type complex (not %T)",
op, res);
Py_DECREF(res);
return NULL;
}
/* Issue #29894: warn if 'res' not of exact type complex. */
if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
"__complex__ returned non-complex (type %.200s). "
"%T.__complex__ must return type complex (not %T). "
"The ability to return an instance of a strict subclass of complex "
"is deprecated, and may be removed in a future version of Python.",
Py_TYPE(res)->tp_name)) {
op, res)) {
Py_DECREF(res);
return NULL;
}
Expand Down
8 changes: 4 additions & 4 deletions Objects/fileobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -66,9 +66,9 @@ PyFile_GetLine(PyObject *f, int n)
}
if (result != NULL && !PyBytes_Check(result) &&
!PyUnicode_Check(result)) {
PyErr_Format(PyExc_TypeError,
"%T.readline() must return type str (not %T)", f, result);
Py_SETREF(result, NULL);
PyErr_SetString(PyExc_TypeError,
"object.readline() returned non-string");
}

if (n < 0 && result != NULL && PyBytes_Check(result)) {
Expand Down Expand Up @@ -191,8 +191,8 @@ PyObject_AsFileDescriptor(PyObject *o)
Py_DECREF(fno);
}
else {
PyErr_SetString(PyExc_TypeError,
"fileno() returned a non-integer");
PyErr_Format(PyExc_TypeError,
"%T.fileno() must return type int (not %T)", o, fno);
Py_DECREF(fno);
return -1;
}
Expand Down
8 changes: 4 additions & 4 deletions Objects/floatobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -297,11 +297,11 @@
if (nb && nb->nb_index) {
PyObject *res = _PyNumber_Index(op);
if (!res) {
return -1;

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expected ‘)’ before ‘{’ token

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expected ‘)’ before ‘{’ token

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expected ‘)’ before ‘{’ token

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syntax error: missing ')' before '{' [C:\a\cpython\cpython\PCbuild\_freeze_module.vcxproj]

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syntax error: missing ')' before '{' [D:\a\cpython\cpython\PCbuild\_freeze_module.vcxproj]

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syntax error: missing ')' before '{' [D:\a\cpython\cpython\PCbuild\_freeze_module.vcxproj]

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syntax error: missing ')' before '{' [C:\a\cpython\cpython\PCbuild\_freeze_module.vcxproj]

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expected ‘)’ before ‘{’ token

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expected ‘)’ before ‘{’ token

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expected ‘)’ before ‘{’ token

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expected ‘)’ before ‘{’ token

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expected ‘)’ before ‘{’ token
}
double val = PyLong_AsDouble(res);
Py_DECREF(res);
return val;

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expected expression before ‘}’ token

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expected expression before ‘}’ token

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expected expression before ‘}’ token

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expected expression before ‘}’ token
}
PyErr_Format(PyExc_TypeError, "must be real number, not %.50s",
Py_TYPE(op)->tp_name);
Expand All @@ -315,16 +315,16 @@
if (!PyFloat_CheckExact(res)) {
if (!PyFloat_Check(res)) {
PyErr_Format(PyExc_TypeError,
"%.50s.__float__ returned non-float (type %.50s)",
Py_TYPE(op)->tp_name, Py_TYPE(res)->tp_name);
"%T.__float__ must return type float (not %T)",
op, res);
Py_DECREF(res);
return -1;
}
if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
"%.50s.__float__ returned non-float (type %.50s). "
"%T.__float__ must return type float (not %T). "
"The ability to return an instance of a strict subclass of float "
"is deprecated, and may be removed in a future version of Python.",
Py_TYPE(op)->tp_name, Py_TYPE(res)->tp_name)) {
op, res) {
Py_DECREF(res);
return -1;
}
Expand Down
5 changes: 3 additions & 2 deletions Objects/funcobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -556,8 +556,9 @@ func_get_annotation_dict(PyFunctionObject *op)
return NULL;
}
if (!PyDict_Check(ann_dict)) {
PyErr_Format(PyExc_TypeError, "__annotate__ returned non-dict of type '%.100s'",
Py_TYPE(ann_dict)->tp_name);
PyErr_Format(PyExc_TypeError,
"__annotate__ must return type dict of type '%T'",
ann_dict);
Py_DECREF(ann_dict);
return NULL;
}
Expand Down
10 changes: 5 additions & 5 deletions Objects/genobject.c
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Expand Up @@ -1076,14 +1076,14 @@ _PyCoro_GetAwaitableIter(PyObject *o)
if (PyCoro_CheckExact(res) || gen_is_coroutine(res)) {
/* __await__ must return an *iterator*, not
a coroutine or another awaitable (see PEP 492) */
PyErr_SetString(PyExc_TypeError,
"__await__() returned a coroutine");
PyErr_Format(PyExc_TypeError,
"%T.__await__ returned a coroutine", o);
Py_CLEAR(res);
} else if (!PyIter_Check(res)) {
PyErr_Format(PyExc_TypeError,
"__await__() returned non-iterator "
"of type '%.100s'",
Py_TYPE(res)->tp_name);
"%T.__await__ must return type iterator "
"of type '%T'",
o, res);
Py_CLEAR(res);
}
}
Expand Down
5 changes: 3 additions & 2 deletions Objects/iterobject.c
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Expand Up @@ -342,8 +342,9 @@ anextawaitable_getiter(anextawaitableobject *obj)
}
Py_SETREF(awaitable, new_awaitable);
if (!PyIter_Check(awaitable)) {
PyErr_SetString(PyExc_TypeError,
"__await__ returned a non-iterable");
PyErr_Format(PyExc_TypeError,
"%T.__await__ must return type iterable (not %T)",
obj, awaitable);
Py_DECREF(awaitable);
return NULL;
}
Expand Down
6 changes: 4 additions & 2 deletions Objects/moduleobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1258,8 +1258,10 @@ module_get_annotations(PyObject *self, void *Py_UNUSED(ignored))
return NULL;
}
if (!PyDict_Check(annotations)) {
PyErr_Format(PyExc_TypeError, "__annotate__ returned non-dict of type '%.100s'",
Py_TYPE(annotations)->tp_name);
PyErr_Format(PyExc_TypeError,
"%T.__annotate__ must return type dict "
"of type '%T'",
self, annotations);
Py_DECREF(annotate);
Py_DECREF(annotations);
Py_DECREF(dict);
Expand Down
10 changes: 4 additions & 6 deletions Objects/object.c
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Original file line number Diff line number Diff line change
Expand Up @@ -779,8 +779,7 @@ PyObject_Repr(PyObject *v)
}
if (!PyUnicode_Check(res)) {
_PyErr_Format(tstate, PyExc_TypeError,
"__repr__ returned non-string (type %.200s)",
Py_TYPE(res)->tp_name);
"%T.__repr__ must return type str (not %T)", v, res);
Py_DECREF(res);
return NULL;
}
Expand Down Expand Up @@ -822,8 +821,7 @@ PyObject_Str(PyObject *v)
}
if (!PyUnicode_Check(res)) {
_PyErr_Format(tstate, PyExc_TypeError,
"__str__ returned non-string (type %.200s)",
Py_TYPE(res)->tp_name);
"%T.__str__ must return type str (not %T)", v, res);
Py_DECREF(res);
return NULL;
}
Expand Down Expand Up @@ -878,8 +876,8 @@ PyObject_Bytes(PyObject *v)
return NULL;
if (!PyBytes_Check(result)) {
PyErr_Format(PyExc_TypeError,
"__bytes__ returned non-bytes (type %.200s)",
Py_TYPE(result)->tp_name);
"%T.__bytes__ must return type bytes (not %T)",
v, result);
Py_DECREF(result);
return NULL;
}
Expand Down
18 changes: 8 additions & 10 deletions Objects/typeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2010,8 +2010,9 @@ type_get_annotations(PyObject *tp, void *Py_UNUSED(closure))
return NULL;
}
if (!PyDict_Check(annotations)) {
PyErr_Format(PyExc_TypeError, "__annotate__ returned non-dict of type '%.100s'",
Py_TYPE(annotations)->tp_name);
PyErr_Format(PyExc_TypeError,
"%T.__annotate__ must return type dict of "
"type '%T'", tp, annotations);
Py_DECREF(annotations);
Py_DECREF(annotate);
Py_DECREF(dict);
Expand Down Expand Up @@ -3238,10 +3239,8 @@ mro_check(PyTypeObject *type, PyObject *mro)
for (i = 0; i < n; i++) {
PyObject *obj = PyTuple_GET_ITEM(mro, i);
if (!PyType_Check(obj)) {
PyErr_Format(
PyExc_TypeError,
"mro() returned a non-class ('%.500s')",
Py_TYPE(obj)->tp_name);
PyErr_Format(PyExc_TypeError,
"%T.mro() must return class (not %T)", type, obj);
return -1;
}
PyTypeObject *base = (PyTypeObject*)obj;
Expand Down Expand Up @@ -9920,9 +9919,7 @@ slot_nb_bool(PyObject *self)
}
else {
PyErr_Format(PyExc_TypeError,
"__bool__ should return "
"bool, returned %s",
Py_TYPE(value)->tp_name);
"%T.__bool__ must return type bool (not %T)", self, value);
result = -1;
}

Expand Down Expand Up @@ -10447,7 +10444,8 @@ slot_bf_getbuffer(PyObject *self, Py_buffer *buffer, int flags)
}
if (!PyMemoryView_Check(ret)) {
PyErr_Format(PyExc_TypeError,
"__buffer__ returned non-memoryview object");
"%T.__buffer__ must return type memoryview (not %T)",
self, ret);
goto fail;
}

Expand Down
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