Fixing SystemError when nb_bool/nb_nonzero sets a Python exception in type_caster<bool>::load (#1976)

Author: YannickJadoul

include/pybind11/cast.h

@@ -1172,6 +1172,8 @@ template <> class type_caster<bool> {
             if (res == 0 || res == 1) {
                 value = (bool) res;
                 return true;
+            } else {
+                PyErr_Clear();
             }
         }
         return false;

tests/test_builtin_casters.py

@@ -318,11 +318,15 @@ def test_numpy_bool():
     import numpy as np
     convert, noconvert = m.bool_passthrough, m.bool_passthrough_noconvert
 
+    def cant_convert(v):
+        pytest.raises(TypeError, convert, v)
+
     # np.bool_ is not considered implicit
     assert convert(np.bool_(True)) is True
     assert convert(np.bool_(False)) is False
     assert noconvert(np.bool_(True)) is True
     assert noconvert(np.bool_(False)) is False
+    cant_convert(np.zeros(2, dtype='int'))
 
 
 def test_int_long():