Make ctypedefed bint behave like normal bint (GH-4660)

Closes https://github.com/cython/cython/issues/3066

Cython/Compiler/PyrexTypes.py

@@ -4929,14 +4929,19 @@ def independent_spanning_type(type1, type2):
             type1 = type1.ref_base_type
         else:
             type2 = type2.ref_base_type
-    if type1 == type2:
+
+    resolved_type1 = type1.resolve()
+    resolved_type2 = type2.resolve()
+    if resolved_type1 == resolved_type2:
         return type1
-    elif (type1 is c_bint_type or type2 is c_bint_type) and (type1.is_numeric and type2.is_numeric):
+    elif ((resolved_type1 is c_bint_type or resolved_type2 is c_bint_type)
+            and (type1.is_numeric and type2.is_numeric)):
         # special case: if one of the results is a bint and the other
         # is another C integer, we must prevent returning a numeric
         # type so that we do not lose the ability to coerce to a
         # Python bool if we have to.
         return py_object_type
+
     span_type = _spanning_type(type1, type2)
     if span_type is None:
         return error_type

tests/run/ctypedef_bint.pyx

+from __future__ import print_function
+
+from cython cimport typeof
+
+ctypedef bint mybool
+
+cdef mybool mybul = True
+cdef bint bul = True
+cdef int num = 42
+
+
+def CondExprNode_to_obj(test):
+    """
+    >>> CondExprNode_to_obj(True)
+    Python object | Python object
+    2
+    >>> CondExprNode_to_obj(False)
+    Python object | Python object
+    84
+    """
+
+    print(typeof(mybul if test else num), "|", typeof(bul if test else num))
+
+    return (mybul if test else num) + (bul if test else num)
+
+
+def BoolBinopNode_to_obj():
+    """
+    >>> BoolBinopNode_to_obj()
+    Python object | Python object
+    2
+    """
+
+    print(typeof(mybul or num), "|", typeof(bul or num))
+
+    return (mybul or num) + (bul or num)
+
+
+cdef int test_bool(mybool arg):
+    return <int>arg
+
+
+def CondExprNode_to_bool(test):
+    """
+    >>> CondExprNode_to_bool(True)
+    bint | bint
+    0
+    >>> CondExprNode_to_bool(False)
+    bint | bint
+    2
+    """
+
+    print(typeof(not mybul if test else mybul), "|", typeof(not bul if test else bul))
+
+    # test_bool() would silently crash if one of the types is cast
+    # to Python object and not just assigned.
+    # It happens when a type is wrongly inferred as Python object
+    # instead of bint or mybool.
+    return test_bool(not mybul if test else mybul) + test_bool(not bul if test else bul)
+
+
+def BoolBinopNode_to_bool():
+    """
+    >>> BoolBinopNode_to_bool()
+    bint | bint
+    2
+    """
+
+    print(typeof(not mybul or mybul), "|", typeof(not bul or bul))
+
+    return test_bool(not mybul or mybul) + test_bool(not bul or bul)