> Yes, fset for most primitives should be f=
orbidden.
Define "most".
That would mean we can't use advise, trace-function, debug-on-entry, or=
elp on them.=C2=A0 There are very legitimate reasons to fset them.
For some of them definitely. I'd draw =
the line between pure functions like car and eq, where those facilities nev=
er make sense and would be ineffective anyway as the functions are compiled=
away or called directly, and impure functions like call-process, where fse=
t is necessary for mocking. As a rule of thumb, I'd suggest to ban fset=
on all symbols that have a byte-code equivalent, and on constant symbols.=
=C2=A0