Hi guys,

compiling CPython from the master branch will result in a git history with the commit https://github.com/python/cpython/commit/211055176157545ce98e6c02b09d624719e6dd30 included and in Lib/inspect.py, however the return type is still like before and behaviour has not changed.

    Python 3.9.0a4+ (heads/master:be79373a78, Mar 11 2020, 16:36:27) 
    [GCC 9.2.1 20190827 (Red Hat 9.2.1-1)] on linux
    Type "help", "copyright", "credits" or "license" for more information.
    >>> import inspect
    >>> inspect.signature(lambda x, y: None).parameters == inspect.signature(lambda y, x: None).parameters
    True
    >>> 

I have been able to confirm this on all builds I've done. To get it to do expected behaviour and return False on above code, I need to patch back the commit that changed OrderedDict to dict (https://raw.githubusercontent.com/Gelbpunkt/python-image/master/inspect.patch is the file I am using to patch). I have compiled against the codebase of https://github.com/python/cpython/commit/be79373a78c0d75fc715ab64253c9b757987a848 and believe this is some issue with the Lib/inspect.py code internally if the patch file can fix it.

Just to show the types are inequal:

Without patch file:

    >>> inspect.signature(lambda x: None).parameters
    mappingproxy({'x': <Parameter "x">})

With patch file:

    >>> inspect.signature(lambda x: None).parameters
    mappingproxy(OrderedDict([('x', <Parameter "x">)]))

Would you create a pull request?

New changeset 611836a69a7a98bb106b4d315ed76a1e17266f4f by Jens Reidel in branch 'master':
bpo-39957: Change Signature.parameters to OrderedDict (GH-18988)
https://github.com/python/cpython/commit/611836a69a7a98bb106b4d315ed76a1e17266f4f