Add error message if @method decorate is in wrong place

Author: saulshanabrook

docs/changelog.md

@@ -7,6 +7,7 @@ _This project uses semantic versioning_
 - Fix pretty printing of lambda functions
 - Add support for subsuming rewrite generated by default function and method definitions
 - Add better error message when using @function in class (thanks @shinawy)
+- Add error method if `@method` decorator is in wrong place
 
 ## 8.0.1 (2024-10-24)
 

python/egglog/egraph.py

@@ -570,6 +570,10 @@ def _generate_class_decls(  # noqa: C901,PLR0912
                 fn = fn.fget
             case _:
                 ref = InitRef(cls_name) if is_init else MethodRef(cls_name, method_name)
+        if isinstance(fn, _WrappedMethod):
+            msg = f"{cls_name}.{method_name} Add the @method(...) decorator above @classmethod or @property"
+
+            raise ValueError(msg)  # noqa: TRY004
         special_function_name: SpecialFunctions | None = (
             "fn-partial" if egg_fn == "unstable-fn" else "fn-app" if egg_fn == "unstable-app" else None
         )

python/egglog/exp/array_api.py

@@ -386,13 +386,13 @@ def var(cls, name: StringLike) -> TupleTupleInt: ...
 
     def __init__(self, length: IntLike, idx_fn: Callable[[Int], TupleInt]) -> None: ...
 
-    @classmethod
     @method(subsume=True)
+    @classmethod
     def single(cls, i: TupleInt) -> TupleTupleInt:
         return TupleTupleInt(Int(1), lambda _: i)
 
-    @classmethod
     @method(subsume=True)
+    @classmethod
     def from_vec(cls, vec: Vec[Int]) -> TupleInt:
         return TupleInt(vec.length(), partial(index_vec_int, vec))