[BUG]: STL casters should probably type cast from `collections.abc`

[meghprkh]

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What version (or hash if on master) of pybind11 are you using?

2.12.0

Problem description

If I have some class inheriting from collections.abc, it would not implicitly cast to corresponding C++ types. Example code shows a reproduction.

This probably makes most sense as nowadays a lot of Python libraries use Mapping/Set as an abstract type instead of dictionary.

Example code with set follows

Reproducible example code

Python class


from collections.abc import MutableSet

class CaselessSet(MutableSet[str]):
 # Using https://stackoverflow.com/a/27531275 as the implementation
 # ... implementation not written for brevity


C++ `mymod`


m.def("set_size", [](set<string>& s) {
 return s.size();
});


`mymod.pyi`:


from collections.abc import Set as AbstractSet
def set_size(set: AbstractSet[str])


usage:


s = CaselessSet('a', 'B')
mymod.set_size(s)

Is this a regression? Put the last known working version here if it is.

Not a regression