isdtype() should raise if parameter is not a dtype

.gitignore

@@ -128,12 +128,12 @@ ENV/
 env.bak/
 venv.bak/
 
-# Spyder project settings
+# Project settings
+.idea
+.ropeproject
 .spyderproject
 .spyproject
-
-# Rope project settings
-.ropeproject
+.vscode
 
 # mkdocs documentation
 /site

array_api_strict/_data_type_functions.py

@@ -167,6 +167,9 @@ def isdtype(
     https://data-apis.org/array-api/latest/API_specification/generated/array_api.isdtype.html
     for more details
     """
+    if not isinstance(dtype, _DType):
+       raise TypeError(f"'dtype' must be a dtype, not a {type(dtype)!r}")
+
     if isinstance(kind, tuple):
         # Disallow nested tuples
         if any(isinstance(k, tuple) for k in kind):

array_api_strict/tests/test_data_type_functions.py

@@ -31,15 +31,17 @@ def test_can_cast(from_, to, expected):
 def test_isdtype_strictness():
     assert_raises(TypeError, lambda: isdtype(float64, 64))
     assert_raises(ValueError, lambda: isdtype(float64, 'f8'))
-
     assert_raises(TypeError, lambda: isdtype(float64, (('integral',),)))
+    assert_raises(TypeError, lambda: isdtype(float64, None))
+    assert_raises(TypeError, lambda: isdtype(np.float64, float64))
+    assert_raises(TypeError, lambda: isdtype(asarray(1.0), float64))
+
     with assert_raises(TypeError), warnings.catch_warnings(record=True) as w:
         warnings.simplefilter("always")
         isdtype(float64, np.object_)
         assert len(w) == 1
         assert issubclass(w[-1].category, UserWarning)
 
-    assert_raises(TypeError, lambda: isdtype(float64, None))
     with assert_raises(TypeError), warnings.catch_warnings(record=True) as w:
         warnings.simplefilter("always")
         isdtype(float64, np.float64)