Improve error message when assigning tuples of incorrect size to a ctuple. Previously, it said "Expected tuple of size 4, got tuple", which is unhelpful and confusing.

2 files changed, 9 insertions, 5 deletions

diff --git a/Cython/Utility/TypeConversion.c b/Cython/Utility/TypeConversion.c
index 6c454d145..9ca29a0f0 100644
--- a/Cython/Utility/TypeConversion.c
+++ b/Cython/Utility/TypeConversion.c
@@ -576,12 +576,16 @@ static {{struct_type_decl}} {{funcname}}(PyObject *);
 static {{struct_type_decl}} {{funcname}}(PyObject * o) {
     {{struct_type_decl}} result;
 
-    if (!PyTuple_Check(o) || PyTuple_GET_SIZE(o) != {{size}}) {
+    if (unlikely(!PyTuple_Check(o))) {
         __Pyx_TypeName o_type_name = __Pyx_PyType_GetName(Py_TYPE(o));
         PyErr_Format(PyExc_TypeError,
-                     "Expected a tuple of size %d, got " __Pyx_FMT_TYPENAME, {{size}}, o_type_name);
+                     "Expected a tuple of size %zd, got " __Pyx_FMT_TYPENAME, (Py_ssize_t) {{size}}, o_type_name);
         __Pyx_DECREF_TypeName(o_type_name);
         goto bad;
+    } else if (unlikely(PyTuple_GET_SIZE(o) != {{size}})) {
+        PyErr_Format(PyExc_TypeError,
+                     "Expected a tuple of size %zd, got size %zd", (Py_ssize_t) {{size}}, PyTuple_GET_SIZE(o));
+        goto bad;
     }
 
 #if CYTHON_ASSUME_SAFE_MACROS && !CYTHON_AVOID_BORROWED_REFS
diff --git a/tests/run/ctuple.pyx b/tests/run/ctuple.pyx
index 2d92f8bad..9412a2cc3 100644
--- a/tests/run/ctuple.pyx
+++ b/tests/run/ctuple.pyx
@@ -8,11 +8,11 @@ def simple_convert(*o):
     >>> simple_convert(1)
     Traceback (most recent call last):
     ...
-    TypeError: Expected a tuple of size 2, got tuple
+    TypeError: Expected a tuple of size 2, got size 1
     >>> simple_convert(1, 2, 3)
     Traceback (most recent call last):
     ...
-    TypeError: Expected a tuple of size 2, got tuple
+    TypeError: Expected a tuple of size 2, got size 3
     """
     cdef (int, double) xy = o
     return xy
@@ -231,7 +231,7 @@ def test_mul_to_ctuple((int, int) ab, int c):
     (1, 2, 1, 2)
     >>> test_mul_to_ctuple((1, 2), 3)
     Traceback (most recent call last):
-    TypeError: Expected a tuple of size 4, got tuple
+    TypeError: Expected a tuple of size 4, got size 6
     """
     result: tuple[cython.int, cython.int, cython.int, cython.int] = ab * c
     return result