[issue39775] inspect.Signature.parameters should be an OrderedDict, not a plain dict

[Antony Lee]

New submission from Antony Lee <anntzer.lee at gmail.com>:

https://bugs.python.org/issue36350 / https://github.com/python/cpython/pull/12412 changed Signature.parameters and BoundArguments.arguments to be plain dicts, not OrderedDicts (for Py3.9a4).  Even though I agree for BoundArguments.arguments (in fact I argued for this behavior in https://bugs.python.org/issue23080), I think Signature.parameters should remain OrderedDicts.  Otherwise, one would get

    >>> inspect.signature(lambda x, y: None).parameters == inspect.signature(lambda y, x: None).parameters
    True

which seems plain wrong (comparing the signature objects themselves still correctly return False because __eq__ explicitly considers parameter order, but one may e.g. want to compare parameters for equality while ignoring the return annotation).

----------
components: Library (Lib)
messages: 362800
nosy: Antony.Lee
priority: normal
severity: normal
status: open
title: inspect.Signature.parameters should be an OrderedDict, not a plain dict
versions: Python 3.9

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<https://bugs.python.org/issue39775>
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