Hi all,
Right now, expressions that evaluates to Optional<()>, Optional<Optional<()>>…
gets special treatment when it’s unused. For example:
func f(s: String) {}
let s: String = “”
s.map(f) // no warning here, even tho the resulting type is `Optional<()>` and
unused.
func g() throws {}
try? g() // no warnings here neither.
This is convenient, but encourages composing map/filter/reduce, etc with
side-effect-ful functions, which we have found a few cases of in our production
code recently. Granted, these cases could’ve been caught with more careful code
reviews. But we wouldn’t have missed them if this “feature” didn’t exist.
I think we should remove the special treatment so that code in the example
above would generate a warning about `()?` being unused. Users can silence it
manually by assigning the result to `_`.
OTOH, this would undermine the convenience of `try?` when the throwing function
don’t return anything.
What do y’all think?
Daniel Duan
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