Make errors Clone.

Manually implement PartialEq, Eq and Clone for types using SendSyncPhantomData.
This is necessary because the default derive imposes an additional PartialEq/Eq/Clone bounds on the phantom type.

Author: raldone01

src/error.rs

@@ -149,7 +149,7 @@ use crate::{FromBytes, Ref};
 /// - [`CastError`]: the error type of reference conversions
 /// - [`TryCastError`]: the error type of fallible reference conversions
 /// - [`TryReadError`]: the error type of fallible read conversions
-#[derive(PartialEq, Eq)]
+#[derive(PartialEq, Eq, Clone)]
 pub enum ConvertError<A, S, V> {
     /// The conversion source was improperly aligned.
     Alignment(A),
@@ -242,15 +242,14 @@ where
 }
 
 /// The error emitted if the conversion source is improperly aligned.
-#[derive(PartialEq, Eq)]
 pub struct AlignmentError<Src, Dst: ?Sized> {
     /// The source value involved in the conversion.
     src: Src,
     /// The inner destination type involved in the conversion.
     ///
     /// INVARIANT: An `AlignmentError` may only be constructed if `Dst`'s
     /// alignment requirement is greater than one.
-    dst: SendSyncPhantomData<Dst>,
+    _dst: SendSyncPhantomData<Dst>,
 }
 
 impl<Src, Dst: ?Sized> AlignmentError<Src, Dst> {
@@ -261,7 +260,7 @@ impl<Src, Dst: ?Sized> AlignmentError<Src, Dst> {
     pub(crate) unsafe fn new_unchecked(src: Src) -> Self {
         // INVARIANT: The caller guarantees that `Dst`'s alignment requirement
         // is greater than one.
-        Self { src, dst: SendSyncPhantomData::default() }
+        Self { src, _dst: SendSyncPhantomData::default() }
     }
 
     /// Produces the source underlying the failed conversion.
@@ -274,7 +273,7 @@ impl<Src, Dst: ?Sized> AlignmentError<Src, Dst> {
         // INVARIANT: `with_src` doesn't change the type of `Dst`, so the
         // invariant that `Dst`'s alignment requirement is greater than one is
         // preserved.
-        AlignmentError { src: new_src, dst: SendSyncPhantomData::default() }
+        AlignmentError { src: new_src, _dst: SendSyncPhantomData::default() }
     }
 
     /// Maps the source value associated with the conversion error.
@@ -299,7 +298,7 @@ impl<Src, Dst: ?Sized> AlignmentError<Src, Dst> {
     /// ```
     #[inline]
     pub fn map_src<NewSrc>(self, f: impl FnOnce(Src) -> NewSrc) -> AlignmentError<NewSrc, Dst> {
-        AlignmentError { src: f(self.src), dst: SendSyncPhantomData::default() }
+        AlignmentError { src: f(self.src), _dst: SendSyncPhantomData::default() }
     }
 
     pub(crate) fn into<S, V>(self) -> ConvertError<Self, S, V> {
@@ -337,6 +336,22 @@ impl<Src, Dst: ?Sized> AlignmentError<Src, Dst> {
     }
 }
 
+impl<Src: Clone, Dst: ?Sized> Clone for AlignmentError<Src, Dst> {
+    #[inline]
+    fn clone(&self) -> Self {
+        AlignmentError { src: self.src.clone(), _dst: SendSyncPhantomData::default() }
+    }
+}
+
+impl<Src: PartialEq, Dst: ?Sized> PartialEq for AlignmentError<Src, Dst> {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        self.src == other.src
+    }
+}
+
+impl<Src: Eq, Dst: ?Sized> Eq for AlignmentError<Src, Dst> {}
+
 impl<Src, Dst: ?Sized + Unaligned> From<AlignmentError<Src, Dst>> for Infallible {
     #[inline(always)]
     fn from(_: AlignmentError<Src, Dst>) -> Infallible {
@@ -408,17 +423,16 @@ impl<Src, Dst: ?Sized, S, V> From<AlignmentError<Src, Dst>>
 }
 
 /// The error emitted if the conversion source is of incorrect size.
-#[derive(PartialEq, Eq)]
 pub struct SizeError<Src, Dst: ?Sized> {
     /// The source value involved in the conversion.
     src: Src,
     /// The inner destination type involved in the conversion.
-    dst: SendSyncPhantomData<Dst>,
+    _dst: SendSyncPhantomData<Dst>,
 }
 
 impl<Src, Dst: ?Sized> SizeError<Src, Dst> {
     pub(crate) fn new(src: Src) -> Self {
-        Self { src, dst: SendSyncPhantomData::default() }
+        Self { src, _dst: SendSyncPhantomData::default() }
     }
 
     /// Produces the source underlying the failed conversion.
@@ -429,7 +443,7 @@ impl<Src, Dst: ?Sized> SizeError<Src, Dst> {
 
     /// Sets the source value associated with the conversion error.
     pub(crate) fn with_src<NewSrc>(self, new_src: NewSrc) -> SizeError<NewSrc, Dst> {
-        SizeError { src: new_src, dst: SendSyncPhantomData::default() }
+        SizeError { src: new_src, _dst: SendSyncPhantomData::default() }
     }
 
     /// Maps the source value associated with the conversion error.
@@ -455,12 +469,12 @@ impl<Src, Dst: ?Sized> SizeError<Src, Dst> {
     /// ```
     #[inline]
     pub fn map_src<NewSrc>(self, f: impl FnOnce(Src) -> NewSrc) -> SizeError<NewSrc, Dst> {
-        SizeError { src: f(self.src), dst: SendSyncPhantomData::default() }
+        SizeError { src: f(self.src), _dst: SendSyncPhantomData::default() }
     }
 
     /// Sets the destination type associated with the conversion error.
     pub(crate) fn with_dst<NewDst: ?Sized>(self) -> SizeError<Src, NewDst> {
-        SizeError { src: self.src, dst: SendSyncPhantomData::default() }
+        SizeError { src: self.src, _dst: SendSyncPhantomData::default() }
     }
 
     /// Converts the error into a general [`ConvertError`].
@@ -507,6 +521,22 @@ impl<Src, Dst: ?Sized> SizeError<Src, Dst> {
     }
 }
 
+impl<Src: Clone, Dst: ?Sized> Clone for SizeError<Src, Dst> {
+    #[inline]
+    fn clone(&self) -> Self {
+        SizeError { src: self.src.clone(), _dst: SendSyncPhantomData::default() }
+    }
+}
+
+impl<Src: PartialEq, Dst: ?Sized> PartialEq for SizeError<Src, Dst> {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        self.src == other.src
+    }
+}
+
+impl<Src: Eq, Dst: ?Sized> Eq for SizeError<Src, Dst> {}
+
 impl<Src, Dst: ?Sized> fmt::Debug for SizeError<Src, Dst> {
     #[inline]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -552,17 +582,17 @@ impl<Src, Dst: ?Sized, A, V> From<SizeError<Src, Dst>> for ConvertError<A, SizeE
 }
 
 /// The error emitted if the conversion source contains invalid data.
-#[derive(PartialEq, Eq)]
+#[derive(Eq)]
 pub struct ValidityError<Src, Dst: ?Sized + TryFromBytes> {
     /// The source value involved in the conversion.
     pub(crate) src: Src,
     /// The inner destination type involved in the conversion.
-    dst: SendSyncPhantomData<Dst>,
+    _dst: SendSyncPhantomData<Dst>,
 }
 
 impl<Src, Dst: ?Sized + TryFromBytes> ValidityError<Src, Dst> {
     pub(crate) fn new(src: Src) -> Self {
-        Self { src, dst: SendSyncPhantomData::default() }
+        Self { src, _dst: SendSyncPhantomData::default() }
     }
 
     /// Produces the source underlying the failed conversion.
@@ -593,7 +623,7 @@ impl<Src, Dst: ?Sized + TryFromBytes> ValidityError<Src, Dst> {
     /// ```
     #[inline]
     pub fn map_src<NewSrc>(self, f: impl FnOnce(Src) -> NewSrc) -> ValidityError<NewSrc, Dst> {
-        ValidityError { src: f(self.src), dst: SendSyncPhantomData::default() }
+        ValidityError { src: f(self.src), _dst: SendSyncPhantomData::default() }
     }
 
     /// Converts the error into a general [`ConvertError`].
@@ -614,6 +644,13 @@ impl<Src, Dst: ?Sized + TryFromBytes> ValidityError<Src, Dst> {
     }
 }
 
+impl<Src: PartialEq, Dst: ?Sized + TryFromBytes> PartialEq for ValidityError<Src, Dst> {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        self.src == other.src
+    }
+}
+
 impl<Src, Dst: ?Sized + TryFromBytes> fmt::Debug for ValidityError<Src, Dst> {
     #[inline]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -1078,4 +1115,13 @@ mod tests {
             Destination type: bool"
         );
     }
+
+    /// A dummy type with no traits implemented.
+    struct NoTraits;
+
+    #[test]
+    fn clone_size_error() {
+        let err = SizeError::<_, NoTraits>::new(&NoTraits);
+        let _err2 = err.clone();
+    }
 }

src/util/mod.rs

@@ -39,13 +39,19 @@ impl<T: ?Sized> Default for SendSyncPhantomData<T> {
 }
 
 impl<T: ?Sized> PartialEq for SendSyncPhantomData<T> {
-    fn eq(&self, other: &Self) -> bool {
-        self.0.eq(&other.0)
+    fn eq(&self, _other: &Self) -> bool {
+        true
     }
 }
 
 impl<T: ?Sized> Eq for SendSyncPhantomData<T> {}
 
+impl<T: ?Sized> Clone for SendSyncPhantomData<T> {
+    fn clone(&self) -> Self {
+        SendSyncPhantomData(PhantomData)
+    }
+}
+
 pub(crate) trait AsAddress {
     fn addr(self) -> usize;
 }