From 0f5e573e3c2aa0d5545736995929051f84f251d0 Mon Sep 17 00:00:00 2001
From: Nathaniel Starkman <nstarman@users.noreply.github.com>
Date: Fri, 28 Jun 2024 12:53:19 -0400
Subject: [PATCH] feat: deprecate multihash (#175)

Signed-off-by: nstarman <nstarman@users.noreply.github.com>
---
 plum/__init__.py  |  3 +++
 plum/signature.py |  4 ++--
 plum/util.py      | 12 +++++++++---
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/plum/__init__.py b/plum/__init__.py
index 9570b4ab..543a620a 100644
--- a/plum/__init__.py
+++ b/plum/__init__.py
@@ -23,6 +23,9 @@
 from .type import resolve_type_hint
 from .util import *  # noqa: F401, F403
 
+# Deprecated
+from .util import multihash  # noqa: F401, F403
+
 # Ensure that type checking is always entirely correct! The default O(1) strategy
 # is super fast, but might yield unpredictable dispatch behaviour. The O(n) strategy
 # actually is not yet available, but we can already opt in to use it.
diff --git a/plum/signature.py b/plum/signature.py
index 9cdbeb90..fd9fb23e 100644
--- a/plum/signature.py
+++ b/plum/signature.py
@@ -13,7 +13,7 @@
 from .repr import repr_short, rich_repr
 from .type import is_faithful, resolve_type_hint
 from .typing import get_type_hints
-from .util import Comparable, Missing, TypeHint, multihash, wrap_lambda
+from .util import Comparable, Missing, TypeHint, wrap_lambda
 
 __all__ = ["Signature", "append_default_args"]
 
@@ -131,7 +131,7 @@ def __eq__(self, other):
         return False
 
     def __hash__(self):
-        return multihash(Signature, *self.types, self.varargs)
+        return hash((Signature, *self.types, self.varargs))
 
     def expand_varargs(self, n: int) -> Tuple[TypeHint, ...]:
         """Expand variable arguments.
diff --git a/plum/util.py b/plum/util.py
index 3e57cc33..fb6ad303 100644
--- a/plum/util.py
+++ b/plum/util.py
@@ -1,6 +1,7 @@
 import abc
 import sys
-from typing import List, Sequence
+import warnings
+from typing import Hashable, List, Sequence
 
 if sys.version_info.minor <= 8:  # pragma: specific no cover 3.9 3.10 3.11
     from typing import Callable
@@ -11,7 +12,6 @@
     "Callable",
     "TypeHint",
     "Missing",
-    "multihash",
     "Comparable",
     "wrap_lambda",
     "is_in_class",
@@ -47,7 +47,7 @@ def __init__(self):
         raise TypeError("`Missing` cannot be instantiated.")
 
 
-def multihash(*args):
+def multihash(*args: Hashable) -> int:
     """Multi-argument order-sensitive hash.
 
     Args:
@@ -56,6 +56,12 @@ def multihash(*args):
     Returns:
         int: Hash.
     """
+    warnings.warn(
+        "The function `multihash` is deprecated and will be removed in a future "
+        "version. Please use `hash(tuple(*args))` instead.",
+        DeprecationWarning,
+        stacklevel=2,
+    )
     return hash(args)