fix: avoid dtype comparison for None report metadata

meta_tests/test_reporting.py

@@ -0,0 +1,16 @@
+from array_api_tests.dtype_helpers import EqualityMapping
+import reporting
+
+
+class MLXDtype:
+    def __eq__(self, other):
+        if other is None:
+            raise TypeError("MLX dtype equality does not support None")
+        return self is other
+
+
+def test_to_json_serializable_none_does_not_compare_to_dtypes(monkeypatch):
+    dtype = MLXDtype()
+    monkeypatch.setattr(reporting, "dtype_to_name", EqualityMapping([(dtype, "float16")]))
+
+    assert reporting.to_json_serializable(None) is None

reporting.py

@@ -17,7 +17,7 @@
     raise ImportError("pytest-json-report is required to run the array API tests")
 
 def to_json_serializable(o):
-    if o in dtype_to_name:
+    if o is not None and o in dtype_to_name:
         return dtype_to_name[o]
     if isinstance(o, (BuiltinFunctionType, FunctionType, type)):
         return o.__name__