Fix equality so that if using on two different types won't try to upcast

Author: saulshanabrook

python/egglog/runtime.py

@@ -584,11 +584,17 @@ def __eq__(self, other: object) -> object:  # type: ignore[override]
         if (method := _get_expr_method(self, "__eq__")) is not None:
             return method(other)
 
-        # TODO: Check if two objects can be upcasted to be the same. If not, then return NotImplemented so other
-        # expr gets a chance to resolve __eq__ which could be a preserved method.
-        from .egraph import BaseExpr, eq  # noqa: PLC0415
+        if not (isinstance(self, RuntimeExpr) and isinstance(other, RuntimeExpr)):
+            return NotImplemented
+        if self.__egg_typed_expr__.tp != other.__egg_typed_expr__.tp:
+            return NotImplemented
 
-        return eq(cast("BaseExpr", self)).to(cast("BaseExpr", other))
+        from .egraph import Fact  # noqa: PLC0415
+
+        return Fact(
+            Declarations.create(self, other),
+            EqDecl(self.__egg_typed_expr__.tp, self.__egg_typed_expr__.expr, other.__egg_typed_expr__.expr),
+        )
 
     def __ne__(self, other: object) -> object:  # type: ignore[override]
         if (method := _get_expr_method(self, "__ne__")) is not None: