[next]: Fix inline lambda pass opcount preserving option (#1687)

In #1531 the `itir.Node` class got a `type` attribute, that until now
contributed to the hash computation of all nodes. As such two
`itir.SymRef` with the same `id`, but one with a type inferred and one
without (i.e. `None`) got a different hash value. Consequently the
`inline_lambda` pass did not recognize them as a reference to the same
symbol and erroneously inlined the expression even with
`opcount_preserving=True`. This PR fixes the hash computation, such that
again `node1 == node2` implies `hash(node1) == hash(node2)`.

src/gt4py/next/iterator/ir.py

@@ -37,10 +37,14 @@ def __str__(self) -> str:
         return pformat(self)
 
     def __hash__(self) -> int:
-        return hash(type(self)) ^ hash(
-            tuple(
-                hash(tuple(v)) if isinstance(v, list) else hash(v)
-                for v in self.iter_children_values()
+        return hash(
+            (
+                type(self),
+                *(
+                    tuple(v) if isinstance(v, list) else v
+                    for (k, v) in self.iter_children_items()
+                    if k not in ["location", "type"]
+                ),
             )
         )
 

tests/next_tests/unit_tests/iterator_tests/transforms_tests/test_inline_lambdas.py

@@ -8,6 +8,7 @@
 
 import pytest
 
+from gt4py.next.type_system import type_specifications as ts
 from gt4py.next.iterator.ir_utils import ir_makers as im
 from gt4py.next.iterator.transforms.inline_lambdas import InlineLambdas
 
@@ -39,6 +40,21 @@
         ),
         im.multiplies_(im.plus(2, 1), im.plus("x", "x")),
     ),
+    (
+        # ensure opcount preserving option works whether `itir.SymRef` has a type or not
+        "typed_ref",
+        im.let("a", im.call("opaque")())(
+            im.plus(im.ref("a", ts.ScalarType(kind=ts.ScalarKind.FLOAT32)), im.ref("a", None))
+        ),
+        {
+            True: im.let("a", im.call("opaque")())(
+                im.plus(  # stays as is
+                    im.ref("a", ts.ScalarType(kind=ts.ScalarKind.FLOAT32)), im.ref("a", None)
+                )
+            ),
+            False: im.plus(im.call("opaque")(), im.call("opaque")()),
+        },
+    ),
 ]