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bpo-43224: Implement substitution of unpacked TypeVarTuple (GH-31800)

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Serhiy Storchaka 2022-03-11 21:43:58 +02:00 • committed by GitHub
parent c83fc9c02c
commit 5b1b9eacb9
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2 changed files with 117 additions and 75 deletions
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49
Lib/typing.py
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@ -1297,30 +1297,39 @@ class _GenericAlias(_BaseGenericAlias, _root=True):
# anything more exotic than a plain `TypeVar`, we need to consider
# edge cases.
if any(isinstance(p, TypeVarTuple) for p in self.__parameters__):
raise NotImplementedError(
"Type substitution for TypeVarTuples is not yet implemented"
)
params = self.__parameters__
# In the example above, this would be {T3: str}
new_arg_by_param = dict(zip(self.__parameters__, args))
new_arg_by_param = {}
for i, param in enumerate(params):
if isinstance(param, TypeVarTuple):
j = len(args) - (len(params) - i - 1)
if j < i:
raise TypeError(f"Too few arguments for {self}")
new_arg_by_param.update(zip(params[:i], args[:i]))
new_arg_by_param[param] = args[i: j]
new_arg_by_param.update(zip(params[i + 1:], args[j:]))
break
else:
new_arg_by_param.update(zip(params, args))
new_args = []
for old_arg in self.__args__:
if _is_unpacked_typevartuple(old_arg):
original_typevartuple = old_arg.__parameters__[0]
new_arg = new_arg_by_param[original_typevartuple]
substfunc = getattr(old_arg, '__typing_subst__', None)
if substfunc:
new_arg = substfunc(new_arg_by_param[old_arg])
else:
substfunc = getattr(old_arg, '__typing_subst__', None)
if substfunc:
new_arg = substfunc(new_arg_by_param[old_arg])
subparams = getattr(old_arg, '__parameters__', ())
if not subparams:
new_arg = old_arg
else:
subparams = getattr(old_arg, '__parameters__', ())
if not subparams:
new_arg = old_arg
else:
subargs = tuple(new_arg_by_param[x] for x in subparams)
new_arg = old_arg[subargs]
subargs = []
for x in subparams:
if isinstance(x, TypeVarTuple):
subargs.extend(new_arg_by_param[x])
else:
subargs.append(new_arg_by_param[x])
new_arg = old_arg[tuple(subargs)]
if self.__origin__ == collections.abc.Callable and isinstance(new_arg, tuple):
# Consider the following `Callable`.
@ -1612,6 +1621,12 @@ class _UnpackGenericAlias(_GenericAlias, _root=True):
# a single item.
return '*' + repr(self.__args__[0])
def __getitem__(self, args):
if (len(self.__parameters__) == 1 and
isinstance(self.__parameters__[0], TypeVarTuple)):
return args
return super().__getitem__(args)
class Generic:
"""Abstract base class for generic types.