Re: `depreciated` attribute for Lua?

[Lars Müller <appgurulars@...>]

The main problem I see is that it is entirely inadequate. Variable attributes are tied to variables, not to values. const affects the variable, not the value inside it (which can be mutated just fine). close closes whatever is in the variable.

Deprecations however should be tied to values, not to variables. Functions are first-class, so what if I do mytable.reduce(t, add)? At this point the variable becomes an argument of reduce (the value is put on the stack when calling), and the deprecation info tied to the variable would be lost.

Attributes only apply to local variables (everything else would complicate tables, since environments are just tables and implementing e.g. const for environmentals would require the ability to mark table slots as immutable). This makes them pretty much useless for libraries: Libraries typically either stuff their functions in API tables (for which attributes can't be used) either by directly assigning functions as myapi.myfunction or by setting the environment to myapi.

That leaves us with deprecation warnings only if the variable (not the value) is directly accessed - that is, only in the scope of the local. This is hardly useful - just leave a few HACK/TODO comments or directly grep for the usages and fix them instead. For functions your library exposes, warn inside the function as bil til said (which is also more flexible - often you just want to deprecate some legacy signatures). For deprecated table fields your library exposes, you can use __index or __newindex metamethods to warn.

On 12.09.23 03:23, Frityet wrote:

My friend had an idea, much like const, a `depreciated` attribute that warns when used

local add<depreciated> = function(a, b)

return a + b

end

add(1, 2) --warning

Thoughts?