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Use the default deserialize_from for Option<T>

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The custom one was functionally identical to the default implementation given by
the Deserialize trait. If someone has benchmarks that the custom one performs
better, we can put it back.
This commit is contained in:
David Tolnay 2017-12-10 21:27:42 -08:00
parent 34936be574
commit ffd2017c6f
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1 changed files with 5 additions and 50 deletions
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55
serde/src/de/impls.rs
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@ -485,7 +485,6 @@ forwarded_impl!((), Box<CStr>, CString::into_boxed_c_str);
struct OptionVisitor<T> {
marker: PhantomData<T>,
}
struct OptionFromVisitor<'a, T: 'a>(&'a mut Option<T>);
impl<'de, T> Visitor<'de> for OptionVisitor<T>
where
@ -522,49 +521,6 @@ where
}
}
impl<'a, 'de, T> Visitor<'de> for OptionFromVisitor<'a, T>
where
T: Deserialize<'de>,
{
type Value = ();
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
formatter.write_str("option")
}
#[inline]
fn visit_unit<E>(self) -> Result<(), E>
where
E: Error,
{
*self.0 = None;
Ok(())
}
#[inline]
fn visit_none<E>(self) -> Result<(), E>
where
E: Error,
{
*self.0 = None;
Ok(())
}
#[inline]
fn visit_some<D>(self, deserializer: D) -> Result<(), D::Error>
where
D: Deserializer<'de>,
{
// The some enum's repr is opaque, so we can't play cute tricks with
// its tag to build this in place unconditionally.
//
// FIXME: investigate whether branching on the old value being Some to
// deserialize_from the value is profitable (probably data-dependent?)
*self.0 = try!(T::deserialize(deserializer).map(Some));
Ok(())
}
}
impl<'de, T> Deserialize<'de> for Option<T>
where
T: Deserialize<'de>,
@ -576,12 +532,11 @@ where
deserializer.deserialize_option(OptionVisitor { marker: PhantomData })
}
fn deserialize_from<D>(&mut self, deserializer: D) -> Result<(), D::Error>
where
D: Deserializer<'de>,
{
deserializer.deserialize_option(OptionFromVisitor(self))
}
// The Some variant's repr is opaque, so we can't play cute tricks with its
// tag to have deserialize_from build the content in place unconditionally.
//
// FIXME: investigate whether branching on the old value being Some to
// deserialize_from the value is profitable (probably data-dependent?)
}
////////////////////////////////////////////////////////////////////////////////