remove unreachable tensor dtype assert (#8190)

it would have failed in `to_dtype`. added some tests for it too

test/test_tensor.py

@@ -424,6 +424,10 @@ class TestTinygrad(unittest.TestCase):
     data = [np.array(1.0), np.array(2.0), np.array(3.0)]
     np.testing.assert_equal(Tensor(data).numpy(), np.array(data))
 
+  def test_tensor_dtype_errors(self):
+    with self.assertRaises(AttributeError): Tensor([3], dtype="typo")
+    with self.assertRaises(TypeError): Tensor([3], dtype=(dtypes.int,))
+
   def test_tensor_bytes(self):
     data = b"abc123"
     t = Tensor(data)

tinygrad/tensor.py

@@ -125,7 +125,6 @@ class Tensor(SimpleMathTrait):
   def __init__(self, data:Union[None, ConstType, bytes, List, Tuple, UOp, MultiLazyBuffer, 'np.ndarray', pathlib.Path],  # type: ignore [name-defined] # noqa: F821
                device:Optional[Union[str, tuple, list]]=None, dtype:Optional[DTypeLike]=None, requires_grad:Optional[bool]=None):
     if dtype is not None: dtype = to_dtype(dtype)
-    assert dtype is None or isinstance(dtype, DType), f"invalid dtype {dtype}"
     if device is None and isinstance(data, pathlib.Path): device = f"DISK:{data.resolve()}"  # keep it on the disk if device is None
     device = tuple(Device.canonicalize(x) for x in device) if isinstance(device, (tuple, list)) else Device.canonicalize(device)