bpo-44791: Fix substitution of ParamSpec in Concatenate with different parameter expressions (GH-27518)
* Substitution with a list of types returns now a tuple of types.
* Substitution with Concatenate returns now a Concatenate with
concatenated lists of arguments.
* Substitution with Ellipsis is not supported.
(cherry picked from commit ecfacc362dd7fef7715dcd94f2e2ca6c622ef115)
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
diff --git a/Lib/typing.py b/Lib/typing.py
index 705331a..aca3f7a 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -598,7 +598,7 @@ def Concatenate(self, parameters):
raise TypeError("The last parameter to Concatenate should be a "
"ParamSpec variable.")
msg = "Concatenate[arg, ...]: each arg must be a type."
- parameters = tuple(_type_check(p, msg) for p in parameters)
+ parameters = (*(_type_check(p, msg) for p in parameters[:-1]), parameters[-1])
return _ConcatenateGenericAlias(self, parameters)
@@ -1274,6 +1274,16 @@ def __init__(self, *args, **kwargs):
_typevar_types=(TypeVar, ParamSpec),
_paramspec_tvars=True)
+ def copy_with(self, params):
+ if isinstance(params[-1], (list, tuple)):
+ return (*params[:-1], *params[-1])
+ if isinstance(params[-1], _ConcatenateGenericAlias):
+ params = (*params[:-1], *params[-1].__args__)
+ elif not isinstance(params[-1], ParamSpec):
+ raise TypeError("The last parameter to Concatenate should be a "
+ "ParamSpec variable.")
+ return super().copy_with(params)
+
class Generic:
"""Abstract base class for generic types.