fix do_devectorize dtype (#17295)

each one derives its dtype from src, not shared

test/null/test_uop_graph.py

@@ -248,6 +248,14 @@ class TestUOpGraph(unittest.TestCase):
     uops = to_uops_list([out])
     self.assertEqual(len(uops), 2)  # +1 for SINK
 
+  def test_devectorize_derives_lane_dtype(self):
+    from tinygrad.codegen import do_devectorize
+    # an Invalid lane derives bool while the value lane derives float: the lane rebuild must derive, not inherit
+    lhs = UOp.stack(UOp.invalid(), UOp.const(None, 1.0).cast(dtypes.float))
+    out = do_devectorize(lhs * lhs)
+    invalid_lane_mul = next(u for u in out.src[0].toposort() if u.op is Ops.MUL)
+    self.assertIs(invalid_lane_mul.dtype, dtypes.bool)
+
   @unittest.skip("this test isn't valid uops")
   def test_noop_vectorize_fold(self):
     d0 = UOp.param(0, dtypes.float, (1,))

tinygrad/codegen/__init__.py

@@ -127,7 +127,7 @@ def do_devectorize(b:UOp):
   src = []
   for idx in itertools.product(*[range(x) for x in b.shape]):
     idx_c = [UOp.const(None, i) for i in idx]
-    src.append(b.replace(src=tuple(x.base if x.base.arg is Invalid else x.index(*idx_c) for x in b.src)))
+    src.append(b.replace(dtype=None, src=tuple(x.base if x.base.arg is Invalid else x.index(*idx_c) for x in b.src)))
   return UOp.stack(*src).reshape(b.shape) if b.op is not Ops.STORE else UOp.group(*src)
 
 def do_stack_wmma(u:UOp):