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Add std::num::Wrapping impl #1072

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Oct 31, 2017
Merged

Add std::num::Wrapping impl #1072

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eb08f03
Add std::num::Wrapping support
UserAB1236872 Oct 31, 2017
a7e4911
Add newlines to ends of files
UserAB1236872 Oct 31, 2017
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17 changes: 17 additions & 0 deletions serde/src/de/impls.rs
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Expand Up @@ -1825,3 +1825,20 @@ where
deserializer.deserialize_enum("Result", VARIANTS, ResultVisitor(PhantomData))
}
}

////////////////////////////////////////////////////////////////////////////////

#[cfg(feature = "std")]
use std::num::Wrapping;

#[cfg(feature = "std")]
impl<'de, T> Deserialize<'de> for Wrapping<T>
where
T: Deserialize<'de>
{
fn deserialize<D>(deserializer: D) -> Result<Wrapping<T>, D::Error>
where D: Deserializer<'de>
{
Deserialize::deserialize(deserializer).map(Wrapping)
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Deserializing a Wapping<u8> from 500 will fail. Does that match your use case?

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Can you clarify? Do you mean that if you deserialize a number that exceeds the max for that type it won't wrap? That's fine, I didn't expect it to use the wrapping functionality at deserialization time.

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Then isn't this something Wrapping(u8::deserialize(deserializer)?) can already accomplish without this impl?

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Yea that's what I meant. Just wanted to make sure. It's backwards compatible to change later if we want to.

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@hcpl If you just want to (de)serialize a Wrapping that's fine, but it becomes somewhat more problematic if you want to Derive a struct containing one. I guess you could decorate every field with a wrapping with a with attribute, but it's overall cleaner to do this.

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@hcpl hcpl Oct 31, 2017 •
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So there are 2 desired behaviours for Wrapping: accept and produce values in the certain range, or only do so for producing values while accepting anything.

Logically speaking, if we were to provide wrapping behaviour in impl Deserialize, we would have to do custom number parsing to wrap any possible number for consistency's sake.

Also, Wrapping<T> doesn't have any bounds on T, which means we end up having to rely on the unstable specialization feature for numeric types.

So yeah, easier to leave things this way.

}
}
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missing newline at end of file

16 changes: 16 additions & 0 deletions serde/src/ser/impls.rs
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Expand Up @@ -664,3 +664,19 @@ impl Serialize for OsString {
self.as_os_str().serialize(serializer)
}
}

////////////////////////////////////////////////////////////////////////////////

#[cfg(feature = "std")]
use std::num::Wrapping;

#[cfg(feature = "std")]
impl<T: Serialize> Serialize for Wrapping<T> {
#[inline]
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: Serializer,
{
self.0.serialize(serializer)
}
}
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also missing newline