RFC: Add a @mustuse function attribute

[CompeyDev]

This RFC proposes a @mustuse attribute, which may be applied to a function, enforcing the usage of a function's return value.

Rendered.

[dv-extrarius]

I know it's used in several languages, but to me "mustuse" is sort of confusing - it sounds like you have to use the function. In C++ there is the gcc attribute warn_unused_result and the standard nodiscard (don't discard the return value or you get a warning), both of which seem better to me

[CompeyDev]

I know it's used in several languages, but to me "mustuse" is sort of confusing - it sounds like you have to use the function. In C++ there is the gcc attribute warn_unused_result and the standard nodiscard (don't discard the return value or you get a warning), both of which seem better to me

I would also prefer @nodiscard on second thought, since @mustuse does initially feel like a dead code lint of sorts.

[Dekkonot]

I'd like it if there was a 'reason' argument supported for this attribute, as it may not be obvious at a glance why a value must be used.

Also, this seems like it'd need a presence in the type system. That's not currently implemented, so this RFC is somewhat hiding a much more complicated proposal behind it. I suggest you (or someone else) write an RFC for attributes to exist in the type system.

[CompeyDev]

I suggest you (or someone else) write an RFC for attributes to exist in the type system.

I was looking to do that as an extension to this RFC once it is merged.