alt Hacker NewsIn my experience using newtypes like this causes a constant shuffle between the original type and the newtype.
If a library exposes Foo and I wrap it in MyFoo implementing some trait, I need to convert to MyFoo everywhere the trait is needed and back to Foo everywhere the original type is expected.
In practice this means cluttering the code with as_foo and as_myfoo all over the place.
You could also impl From or Deref for one direction of the conversion, but it makes the code less clear in my opinion.
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honestly in my experience it rarely matters (if you care about stable APIs) as most types you want to have at an API boundary are written (or auto generated) by you
this leaves a few often small types like `DateTime<Utc>`, which you can handle with serde serialization function overwrite attributes or automatic conversions not even needing new types (through some of this attributes could be better designed)
serde is not perfect but pretty decent, but IMHO the proc macros it provides need some love/a v2 rewrite, which would only affect impl. code gen and as such is fully backward compatible, can be mixed with old code and can be from a different author (i.e. it doesn't have the problem)
Anyway that doesn't make the problem go away, just serialization/serde is both the best and worst example. (Best as it's extremely wide spread, "good enough" but not perfect, which is poison for ecosystem evolution, worst as serialization is enough of a special case to make it's best solution be potentially unusable to solve the generic problem (e.g. reflections)).
One strategy I like is to declare “view” types for serialization and deserialization, because you’re going to be doing that anyway if your serialized format is meant to be compatible across versions anyway.
Serde also comes with a bunch of attributes and features to make it easy to short-circuit this stuff ad hoc.
I know this only solves the serialization use case, but that seems to be where most people run into this.