> I think option 2 is bad as it gives users no way to know which functions are
> strict in their value argument without knowing the implementation or us
> documenting every function with the strictness properties. We could do the
> latter but the API would be simpler if we just said that all functions are
> strict in their key and value arguments.

This is even a problem of current API. Although most of the functions
are strict in keys, it is not mentioned at any place in the
documentation.

That's mostly an oversight. After we agreed a while back that the API should be consistently key strict I intended to update the documentation, but never got around to it.

-- Johan