bugfix do not reset shapetracker of 0 size lazybuffer (#3096)

it might be coming from an expand, and resetting results incorrect stride. caught by interpreted backend

test/imported/test_indexing.py

@@ -1149,7 +1149,8 @@ class TestIndexing(unittest.TestCase):
     # this isn't technically necessary, but matches NumPy stride calculations.
     # TODO not too sure about this
     # numpy_testing_assert_equal_helper((60, 20, 5), z.lazydata.st.real_strides())
-    self.assertTrue(z.lazydata.st.contiguous)
+    # TODO: should this be contiguous?
+    # self.assertTrue(z.lazydata.st.contiguous)
 
   # TODO bool indexing
   # TODO data_ptr()

test/test_lazybuffer.py

@@ -50,5 +50,11 @@ class TestLazyBuffer(unittest.TestCase):
     b = Tensor([1, 2, 3], f"{Device.DEFAULT}:0")
     assert a.device == b.device
 
+  def test_shrink_const_into_zero(self):
+    a = Tensor.zeros(4,4,4).shrink((None, (0,0), None))
+    b = Tensor.zeros(4,1,4)
+    c = a.cat(b, dim=1)
+    np.testing.assert_allclose(c.numpy(), np.concatenate((a.numpy(), b.numpy()), axis=1))
+
 if __name__ == "__main__":
   unittest.main()

tinygrad/lazy.py

@@ -18,7 +18,7 @@ sys.setrecursionlimit(10000)
 lazycache: Dict[Any, ReferenceType[LazyBuffer]] = {}
 def create_lazybuffer(device:str, st:ShapeTracker, dtype:DType, op:Optional[Op]=None, arg:Any=None, srcs:Tuple[LazyBuffer, ...]=(),
                       base:Optional[LazyBuffer]=None, enable_cache=bool(getenv("LAZYCACHE", 1))):
-  if st.size == 0: st, op, arg, srcs, base = ShapeTracker.from_shape(st.shape), LoadOps.CONST, 0, (), None
+  if st.size == 0: op, arg, srcs, base = LoadOps.CONST, 0, (), None
 
   cache_key = (device, st, dtype, op, arg, tuple(ref(x) for x in srcs)) if base is None else (st, ref(base))
   if (rret := lazycache.get(cache_key, None)): return cast(LazyBuffer, rret())  # NOTE: this should always be a live reference