bug#64537: mix lists and vectors when using backquote

[Stefan Kangas]

Shynur Xie <one.last.kiss@outlook.com> writes:

> The docstring of ‘backquote’ says “vectors work just like lists”.
> Should we also clarify that mixing lists and vectors these 2 way:
>
>     `(... ,@[...])  ; by contrast: `(,@[] 1)  => (1)
>     `[,@'()]        ; by contrast: `[1 ,@'()] => [1]
>
> will lead to unexpected behavior?  Or suggest not doing so?  Or let
> ‘backquote’ detect this and signal an error?

Copying in Stefan Monnier.