Specialcase bound methods in singledispatchmethods

Removed _dispatchmethod=False from register property, because it was an incorrect assumption.

Author: johnslavik

Lib/functools.py

@@ -888,21 +888,24 @@ def _find_impl(cls, registry):
             match = t
     return registry.get(match)
 
-def _get_dispatch_param(func, *, _insideclass=False):
+def _get_dispatch_param(func, *, _dispatchmethod=False):
     """Finds the first positional and user-specified parameter in a callable
     or descriptor.
 
     Used by singledispatch for registration by type annotation of the parameter.
     """
     # Fast path for typical callables and descriptors.
     # idx is 0 when singledispatch() and 1 when singledispatchmethod().
-    idx = _insideclass
     if isinstance(func, staticmethod):
         idx = 0
         func = func.__func__
     elif isinstance(func, classmethod):
         func = func.__func__
         idx = 1
+    elif _dispatchmethod and isinstance(func, MethodType):
+        idx = 0
+    else:
+        idx = _dispatchmethod
     if isinstance(func, FunctionType) and not hasattr(func, "__wrapped__"):
         # Method from inspect._signature_from_function.
         func_code = func.__code__
@@ -967,7 +970,7 @@ def _is_valid_dispatch_type(cls):
         return (isinstance(cls, UnionType) and
                 all(isinstance(arg, type) for arg in cls.__args__))
 
-    def register(cls, func=None, _insideclass=False):
+    def register(cls, func=None, _dispatchmethod=False):
         """generic_func.register(cls, func) -> func
 
         Registers a new implementation for the given *cls* on a *generic_func*.
@@ -992,7 +995,7 @@ def register(cls, func=None, _insideclass=False):
                 )
             func = cls
 
-            argname = _get_dispatch_param(func, _insideclass=_insideclass)
+            argname = _get_dispatch_param(func, _dispatchmethod=_dispatchmethod)
             if argname is None:
                 raise TypeError(
                     f"Invalid first argument to `register()`: {func!r} "
@@ -1071,12 +1074,12 @@ def __init__(self, func):
         self.dispatcher = singledispatch(func)
         self.func = func
 
-    def register(self, cls, method=None, _insideclass=True):
+    def register(self, cls, method=None, _dispatchmethod=True):
         """generic_method.register(cls, func) -> func
 
         Registers a new implementation for the given *cls* on a *generic_method*.
         """
-        return self.dispatcher.register(cls, func=method, _insideclass=_insideclass)
+        return self.dispatcher.register(cls, func=method, _dispatchmethod=_dispatchmethod)
 
     def __get__(self, obj, cls=None):
         return _singledispatchmethod_get(self, obj, cls)
@@ -1151,8 +1154,7 @@ def __wrapped__(self):
 
     @property
     def register(self):
-        # This is called from outside of the class with singledispatchmethod.
-        return partial(self._unbound.register, _insideclass=False)
+        return self._unbound.register
 
 
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