diff --git a/implementations/rust/preserves-schema/src/support/mod.rs b/implementations/rust/preserves-schema/src/support/mod.rs
index 1f8066b..f4049ce 100644
--- a/implementations/rust/preserves-schema/src/support/mod.rs
+++ b/implementations/rust/preserves-schema/src/support/mod.rs
@@ -3,7 +3,6 @@ pub use lazy_static::lazy_static;
 use preserves::value::ArcValue;
 use preserves::value::Domain;
 use preserves::value::Embeddable;
-use preserves::value::IOResult;
 use preserves::value::IOValue;
 use preserves::value::NestedValue;
 use preserves::value::NoEmbeddedDomainCodec;
@@ -11,9 +10,10 @@ use preserves::value::Value;
 
 use std::convert::From;
 use std::convert::TryFrom;
+use std::io;
 use std::sync::Arc;
 
-pub fn decode_lit<D: Embeddable, N: NestedValue<D>>(bs: &[u8]) -> IOResult<N> {
+pub fn decode_lit<D: Embeddable, N: NestedValue<D>>(bs: &[u8]) -> io::Result<N> {
     preserves::value::packed::from_bytes(bs, NoEmbeddedDomainCodec)
 }
 
diff --git a/implementations/rust/preserves/src/lib.rs b/implementations/rust/preserves/src/lib.rs
index dad9ebc..85e4b46 100644
--- a/implementations/rust/preserves/src/lib.rs
+++ b/implementations/rust/preserves/src/lib.rs
@@ -7,6 +7,7 @@ pub mod value;
 
 #[cfg(test)]
 mod dom {
+    use std::io;
     use super::value::*;
 
     #[derive(Debug, Hash, Clone, Ord, PartialEq, Eq, PartialOrd)]
@@ -17,7 +18,7 @@ mod dom {
 
     impl Domain for Dom {}
 
-    fn dom_as_preserves(v: &Dom) -> IOResult<UnwrappedIOValue> {
+    fn dom_as_preserves(v: &Dom) -> io::Result<UnwrappedIOValue> {
         Ok(match v {
             Dom::One => Value::ByteString(vec![255, 255, 255, 255]),
             Dom::Two => Value::symbol(&format!("Dom::{:?}", v)),
diff --git a/implementations/rust/preserves/src/value/domain.rs b/implementations/rust/preserves/src/value/domain.rs
index cf4a0a2..8af8dec 100644
--- a/implementations/rust/preserves/src/value/domain.rs
+++ b/implementations/rust/preserves/src/value/domain.rs
@@ -1,6 +1,7 @@
+use std::io;
+
 use super::BinarySource;
 use super::Embeddable;
-use super::IOResult;
 use super::IOValue;
 use super::Reader;
 use super::Writer;
@@ -11,7 +12,7 @@ pub trait DomainDecode<D: Embeddable> {
         &mut self,
         src: &'src mut S,
         read_annotations: bool,
-    ) -> IOResult<D>;
+    ) -> io::Result<D>;
 }
 
 pub trait DomainEncode<D: Embeddable> {
@@ -19,7 +20,7 @@ pub trait DomainEncode<D: Embeddable> {
         &mut self,
         w: &mut W,
         d: &D,
-    ) -> IOResult<()>;
+    ) -> io::Result<()>;
 }
 
 pub struct IOValueDomainCodec;
@@ -29,7 +30,7 @@ impl DomainDecode<IOValue> for IOValueDomainCodec {
         &mut self,
         src: &'src mut S,
         read_annotations: bool,
-    ) -> IOResult<IOValue> {
+    ) -> io::Result<IOValue> {
         PackedReader::new(src, IOValueDomainCodec).demand_next(read_annotations)
     }
 }
@@ -39,7 +40,7 @@ impl DomainEncode<IOValue> for IOValueDomainCodec {
         &mut self,
         w: &mut W,
         d: &IOValue,
-    ) -> IOResult<()> {
+    ) -> io::Result<()> {
         w.write(self, d)
     }
 }
@@ -51,7 +52,7 @@ impl<D: Embeddable> DomainDecode<D> for NoEmbeddedDomainCodec {
         &mut self,
         _src: &'src mut S,
         _read_annotations: bool,
-    ) -> IOResult<D> {
+    ) -> io::Result<D> {
         Err(std::io::Error::new(std::io::ErrorKind::Unsupported, "Embedded values not supported here"))
     }
 }
@@ -61,7 +62,7 @@ impl<D: Embeddable> DomainEncode<D> for NoEmbeddedDomainCodec {
         &mut self,
         _w: &mut W,
         _d: &D,
-    ) -> IOResult<()> {
+    ) -> io::Result<()> {
         Err(std::io::Error::new(std::io::ErrorKind::Unsupported, "Embedded values not supported here"))
     }
 }
diff --git a/implementations/rust/preserves/src/value/mod.rs b/implementations/rust/preserves/src/value/mod.rs
index a3e9abd..7d64231 100644
--- a/implementations/rust/preserves/src/value/mod.rs
+++ b/implementations/rust/preserves/src/value/mod.rs
@@ -40,8 +40,6 @@ pub use ser::Serializer;
 pub use ser::to_value;
 pub use writer::Writer;
 
-pub type IOResult<T> = std::result::Result<T, std::io::Error>;
-
 pub fn invert_map<A, B>(m: &Map<A, B>) -> Map<B, A>
     where A: Clone, B: Clone + Ord
 {
diff --git a/implementations/rust/preserves/src/value/packed/mod.rs b/implementations/rust/preserves/src/value/packed/mod.rs
index 7c2e47a..2620632 100644
--- a/implementations/rust/preserves/src/value/packed/mod.rs
+++ b/implementations/rust/preserves/src/value/packed/mod.rs
@@ -5,26 +5,28 @@ pub mod writer;
 pub use reader::PackedReader;
 pub use writer::PackedWriter;
 
-use super::{BinarySource, DomainDecode, Embeddable, IOResult, IOValue, IOValueDomainCodec, NestedValue, Reader};
+use std::io;
+
+use super::{BinarySource, DomainDecode, Embeddable, IOValue, IOValueDomainCodec, NestedValue, Reader};
 
 pub fn from_bytes<D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>>(
     bs: &[u8],
     decode_embedded: Dec,
-) -> IOResult<N> {
+) -> io::Result<N> {
     super::BytesBinarySource::new(bs).packed(decode_embedded).demand_next(false)
 }
 
-pub fn iovalue_from_bytes(bs: &[u8]) -> IOResult<IOValue> {
+pub fn iovalue_from_bytes(bs: &[u8]) -> io::Result<IOValue> {
     from_bytes(bs, IOValueDomainCodec)
 }
 
 pub fn annotated_from_bytes<D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>>(
     bs: &[u8],
     decode_embedded: Dec,
-) -> IOResult<N> {
+) -> io::Result<N> {
     super::BytesBinarySource::new(bs).packed(decode_embedded).demand_next(true)
 }
 
-pub fn annotated_iovalue_from_bytes(bs: &[u8]) -> IOResult<IOValue> {
+pub fn annotated_iovalue_from_bytes(bs: &[u8]) -> io::Result<IOValue> {
     annotated_from_bytes(bs, IOValueDomainCodec)
 }
diff --git a/implementations/rust/preserves/src/value/packed/reader.rs b/implementations/rust/preserves/src/value/packed/reader.rs
index b127c1c..24adc8e 100644
--- a/implementations/rust/preserves/src/value/packed/reader.rs
+++ b/implementations/rust/preserves/src/value/packed/reader.rs
@@ -6,13 +6,13 @@ use num::traits::cast::{FromPrimitive, ToPrimitive};
 use std::borrow::Cow;
 use std::convert::TryFrom;
 use std::convert::TryInto;
+use std::io;
 use std::marker::PhantomData;
 
 use super::constants::Tag;
 use super::super::{
     DomainDecode,
     Embeddable,
-    IOResult,
     Map,
     NestedValue,
     Record,
@@ -39,16 +39,16 @@ impl<'de, 'src, D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>, S: Binar
     BinarySource<'de>
     for PackedReader<'de, 'src, D, N, Dec, S>
 {
-    fn skip(&mut self) -> IOResult<()> {
+    fn skip(&mut self) -> io::Result<()> {
         self.source.skip()
     }
-    fn peek(&mut self) -> IOResult<u8> {
+    fn peek(&mut self) -> io::Result<u8> {
         self.source.peek()
     }
-    fn readbytes(&mut self, count: usize) -> IOResult<Cow<'de, [u8]>> {
+    fn readbytes(&mut self, count: usize) -> io::Result<Cow<'de, [u8]>> {
         self.source.readbytes(count)
     }
-    fn readbytes_into(&mut self, bs: &mut [u8]) -> IOResult<()> {
+    fn readbytes_into(&mut self, bs: &mut [u8]) -> io::Result<()> {
         self.source.readbytes_into(bs)
     }
 }
@@ -62,7 +62,7 @@ impl<'de, 'src, D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>, S: Binar
         PackedReader { source, decode_embedded, phantom: PhantomData }
     }
 
-    fn read(&mut self) -> IOResult<u8> {
+    fn read(&mut self) -> io::Result<u8> {
         let v = self.peek()?;
         self.skip()?;
         Ok(v)
@@ -75,7 +75,7 @@ impl<'de, 'src, D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>, S: Binar
         }
     }
 
-    fn varint(&mut self) -> IOResult<usize> {
+    fn varint(&mut self) -> io::Result<usize> {
         let mut shift = 0;
         let mut acc: usize = 0;
         loop {
@@ -86,7 +86,7 @@ impl<'de, 'src, D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>, S: Binar
         }
     }
 
-    fn peekend(&mut self) -> IOResult<bool> {
+    fn peekend(&mut self) -> io::Result<bool> {
         if self.peek()? == Tag::End.into() {
             self.skip()?;
             Ok(true)
@@ -129,7 +129,7 @@ impl<'de, 'src, D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>, S: Binar
         }
     }
 
-    fn read_signed_integer(&mut self, count: usize) -> IOResult<SignedInteger> {
+    fn read_signed_integer(&mut self, count: usize) -> io::Result<SignedInteger> {
         if count == 0 {
             return Ok(SignedInteger::from(0_i128));
         }
@@ -228,7 +228,7 @@ impl<'de, 'src, D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>, S: Binar
     Reader<'de, D, N>
     for PackedReader<'de, 'src, D, N, Dec, S>
 {
-    fn next(&mut self, read_annotations: bool) -> IOResult<Option<N>> {
+    fn next(&mut self, read_annotations: bool) -> io::Result<Option<N>> {
         match self.peek() {
             Err(e) if is_eof_io_error(&e) => return Ok(None),
             Err(e) => return Err(e),
@@ -296,7 +296,7 @@ impl<'de, 'src, D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>, S: Binar
             }
             Tag::Record => {
                 let iter = DelimitedStream { reader: self.configured(read_annotations) };
-                let vs = iter.collect::<IOResult<Vec<N>>>()?;
+                let vs = iter.collect::<io::Result<Vec<N>>>()?;
                 if vs.is_empty() {
                     return Err(io_syntax_error("Too few elements in encoded record"))
                 }
@@ -304,7 +304,7 @@ impl<'de, 'src, D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>, S: Binar
             }
             Tag::Sequence => {
                 let iter = DelimitedStream { reader: self.configured(read_annotations) };
-                let vs = iter.collect::<IOResult<Vec<N>>>()?;
+                let vs = iter.collect::<io::Result<Vec<N>>>()?;
                 Value::Sequence(vs).wrap()
             }
             Tag::Set => {
@@ -456,7 +456,7 @@ impl<'a, 'de, 'src, D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>, S: B
     Iterator
     for DelimitedStream<'a, 'de, 'src, D, N, Dec, S>
 {
-    type Item = IOResult<N>;
+    type Item = io::Result<N>;
     fn next(&mut self) -> Option<Self::Item> {
         match self.reader.reader.peekend() {
             Err(e) => Some(Err(e)),
@@ -466,7 +466,7 @@ impl<'a, 'de, 'src, D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>, S: B
     }
 }
 
-fn decodestr(cow: Cow<'_, [u8]>) -> IOResult<Cow<'_, str>> {
+fn decodestr(cow: Cow<'_, [u8]>) -> io::Result<Cow<'_, str>> {
     match cow {
         Cow::Borrowed(bs) =>
             Ok(Cow::Borrowed(std::str::from_utf8(bs).map_err(|_| io_syntax_error("Invalid UTF-8"))?)),
diff --git a/implementations/rust/preserves/src/value/packed/writer.rs b/implementations/rust/preserves/src/value/packed/writer.rs
index b583874..978565c 100644
--- a/implementations/rust/preserves/src/value/packed/writer.rs
+++ b/implementations/rust/preserves/src/value/packed/writer.rs
@@ -1,6 +1,7 @@
 use num::bigint::BigInt;
 use num::cast::ToPrimitive;
 use std::convert::TryInto;
+use std::io;
 use std::mem;
 use std::ops::{Deref, DerefMut};
 use super::constants::Tag;
@@ -8,7 +9,6 @@ use super::super::DomainEncode;
 use super::super::Embeddable;
 use super::super::IOValue;
 use super::super::IOValueDomainCodec;
-use super::super::IOResult;
 use super::super::NestedValue;
 
 use super::super::writer::{Writer, AnnotationWriter, CompoundWriter, varint};
@@ -78,7 +78,7 @@ impl PackedWriter<Vec<u8>> {
     pub fn encode<D: Embeddable, N: NestedValue<D>, Enc: DomainEncode<D>>(
         enc: &mut Enc,
         v: &N,
-    ) -> IOResult<Vec<u8>> {
+    ) -> io::Result<Vec<u8>> {
         let mut buf: Vec<u8> = Vec::new();
         let w = &mut PackedWriter::new(&mut buf);
         w.write(enc, v)?;
@@ -99,18 +99,18 @@ impl<W: std::io::Write> PackedWriter<W> {
         self.0.deref_mut()
     }
 
-    pub fn write_byte(&mut self, b: u8) -> IOResult<()> {
+    pub fn write_byte(&mut self, b: u8) -> io::Result<()> {
         self.w().write_all(&[b])
     }
 
-    pub fn write_medium_integer(&mut self, bs: &[u8]) -> IOResult<()> {
+    pub fn write_medium_integer(&mut self, bs: &[u8]) -> io::Result<()> {
         let count: u8 = bs.len().try_into().unwrap();
         if !(1..=16).contains(&count) { panic!("Invalid medium_integer count: {}", count) }
         self.write_byte(Tag::MediumInteger(count).into())?;
         self.w().write_all(bs)
     }
 
-    pub fn write_atom(&mut self, tag: Tag, bs: &[u8]) -> IOResult<()> {
+    pub fn write_atom(&mut self, tag: Tag, bs: &[u8]) -> io::Result<()> {
         self.write_byte(tag.into())?;
         varint(&mut self.w(), bs.len().try_into().unwrap())?;
         self.w().write_all(bs)
@@ -152,7 +152,7 @@ impl BinaryOrderWriter {
         self.0.last_mut().unwrap()
     }
 
-    fn finish<W: WriteWriter>(mut self, w: &mut W) -> IOResult<()> {
+    fn finish<W: WriteWriter>(mut self, w: &mut W) -> io::Result<()> {
         if !self.buffer().is_empty() { panic!("Missing final delimit()"); }
         self.items_mut().pop();
         self.items_mut().sort();
@@ -165,51 +165,51 @@ impl BinaryOrderWriter {
 }
 
 pub trait WriteWriter: Writer {
-    fn write_raw_bytes(&mut self, v: &[u8]) -> IOResult<()>;
-    fn write_tag(&mut self, tag: Tag) -> IOResult<()> {
+    fn write_raw_bytes(&mut self, v: &[u8]) -> io::Result<()>;
+    fn write_tag(&mut self, tag: Tag) -> io::Result<()> {
         self.write_raw_bytes(&[tag.into()])
     }
 }
 
 impl<W: std::io::Write> WriteWriter for PackedWriter<W> {
-    fn write_raw_bytes(&mut self, v: &[u8]) -> IOResult<()> {
+    fn write_raw_bytes(&mut self, v: &[u8]) -> io::Result<()> {
         self.w().write_all(v)
     }
 }
 
 impl WriteWriter for BinaryOrderWriter {
-    fn write_raw_bytes(&mut self, v: &[u8]) -> IOResult<()> {
+    fn write_raw_bytes(&mut self, v: &[u8]) -> io::Result<()> {
         use std::io::Write;
         self.buffer().write_all(v)
     }
 }
 
 impl<T: WriteWriter> AnnotationWriter for T {
-    fn start_annotation(&mut self) -> IOResult<()> {
+    fn start_annotation(&mut self) -> io::Result<()> {
         Ok(self.write_tag(Tag::Annotation)?)
     }
 
-    fn start_value(&mut self) -> IOResult<()> {
+    fn start_value(&mut self) -> io::Result<()> {
         Ok(())
     }
 }
 
 impl<W: std::io::Write> CompoundWriter for PackedWriter<W> {
-    fn extend(&mut self) -> IOResult<()> {
+    fn extend(&mut self) -> io::Result<()> {
         Ok(())
     }
 
-    fn delimit(&mut self) -> IOResult<()> {
+    fn delimit(&mut self) -> io::Result<()> {
         Ok(())
     }
 }
 
 impl CompoundWriter for BinaryOrderWriter {
-    fn extend(&mut self) -> IOResult<()> {
+    fn extend(&mut self) -> io::Result<()> {
         Ok(())
     }
 
-    fn delimit(&mut self) -> IOResult<()> {
+    fn delimit(&mut self) -> io::Result<()> {
         self.items_mut().push(vec![]);
         Ok(())
     }
@@ -228,67 +228,67 @@ impl Writer for BinaryOrderWriter {
     type SetWriter = BinaryOrderWriter;
     type EmbeddedWriter = PackedWriter<Vec<u8>>;
 
-    binary_order_writer_method!(mut align(natural_chunksize: u64) -> IOResult<()>);
+    binary_order_writer_method!(mut align(natural_chunksize: u64) -> io::Result<()>);
 
-    fn start_annotations(&mut self) -> IOResult<Self::AnnWriter> {
+    fn start_annotations(&mut self) -> io::Result<Self::AnnWriter> {
         Ok(self.pop())
     }
-    fn end_annotations(&mut self, ann: Self::AnnWriter) -> IOResult<()> {
+    fn end_annotations(&mut self, ann: Self::AnnWriter) -> io::Result<()> {
         self.push(ann);
         Ok(())
     }
 
-    binary_order_writer_method!(mut write_bool(v: bool) -> IOResult<()>);
+    binary_order_writer_method!(mut write_bool(v: bool) -> io::Result<()>);
 
-    binary_order_writer_method!(mut write_f32(v: f32) -> IOResult<()>);
-    binary_order_writer_method!(mut write_f64(v: f64) -> IOResult<()>);
+    binary_order_writer_method!(mut write_f32(v: f32) -> io::Result<()>);
+    binary_order_writer_method!(mut write_f64(v: f64) -> io::Result<()>);
 
-    binary_order_writer_method!(mut write_i8(v: i8) -> IOResult<()>);
-    binary_order_writer_method!(mut write_u8(v: u8) -> IOResult<()>);
-    binary_order_writer_method!(mut write_i16(v: i16) -> IOResult<()>);
-    binary_order_writer_method!(mut write_u16(v: u16) -> IOResult<()>);
-    binary_order_writer_method!(mut write_i32(v: i32) -> IOResult<()>);
-    binary_order_writer_method!(mut write_u32(v: u32) -> IOResult<()>);
-    binary_order_writer_method!(mut write_i64(v: i64) -> IOResult<()>);
-    binary_order_writer_method!(mut write_u64(v: u64) -> IOResult<()>);
-    binary_order_writer_method!(mut write_i128(v: i128) -> IOResult<()>);
-    binary_order_writer_method!(mut write_u128(v: u128) -> IOResult<()>);
-    binary_order_writer_method!(mut write_int(v: &BigInt) -> IOResult<()>);
+    binary_order_writer_method!(mut write_i8(v: i8) -> io::Result<()>);
+    binary_order_writer_method!(mut write_u8(v: u8) -> io::Result<()>);
+    binary_order_writer_method!(mut write_i16(v: i16) -> io::Result<()>);
+    binary_order_writer_method!(mut write_u16(v: u16) -> io::Result<()>);
+    binary_order_writer_method!(mut write_i32(v: i32) -> io::Result<()>);
+    binary_order_writer_method!(mut write_u32(v: u32) -> io::Result<()>);
+    binary_order_writer_method!(mut write_i64(v: i64) -> io::Result<()>);
+    binary_order_writer_method!(mut write_u64(v: u64) -> io::Result<()>);
+    binary_order_writer_method!(mut write_i128(v: i128) -> io::Result<()>);
+    binary_order_writer_method!(mut write_u128(v: u128) -> io::Result<()>);
+    binary_order_writer_method!(mut write_int(v: &BigInt) -> io::Result<()>);
 
-    binary_order_writer_method!(mut write_string(v: &str) -> IOResult<()>);
-    binary_order_writer_method!(mut write_bytes(v: &[u8]) -> IOResult<()>);
-    binary_order_writer_method!(mut write_symbol(v: &str) -> IOResult<()>);
+    binary_order_writer_method!(mut write_string(v: &str) -> io::Result<()>);
+    binary_order_writer_method!(mut write_bytes(v: &[u8]) -> io::Result<()>);
+    binary_order_writer_method!(mut write_symbol(v: &str) -> io::Result<()>);
 
-    fn start_record(&mut self, _field_count: Option<usize>) -> IOResult<Self::SeqWriter> {
+    fn start_record(&mut self, _field_count: Option<usize>) -> io::Result<Self::SeqWriter> {
         self.write_tag(Tag::Record)?;
         Ok(self.pop())
     }
-    fn start_sequence(&mut self, _item_count: Option<usize>) -> IOResult<Self::SeqWriter> {
+    fn start_sequence(&mut self, _item_count: Option<usize>) -> io::Result<Self::SeqWriter> {
         self.write_tag(Tag::Sequence)?;
         Ok(self.pop())
     }
-    fn end_seq(&mut self, seq: Self::SeqWriter) -> IOResult<()> {
+    fn end_seq(&mut self, seq: Self::SeqWriter) -> io::Result<()> {
         self.push(seq);
         self.write_tag(Tag::End)
     }
 
-    fn start_set(&mut self, _item_count: Option<usize>) -> IOResult<Self::SetWriter> {
+    fn start_set(&mut self, _item_count: Option<usize>) -> io::Result<Self::SetWriter> {
         self.write_tag(Tag::Set)?;
         Ok(BinaryOrderWriter::new())
     }
-    fn start_dictionary(&mut self, _entry_count: Option<usize>) -> IOResult<Self::SetWriter> {
+    fn start_dictionary(&mut self, _entry_count: Option<usize>) -> io::Result<Self::SetWriter> {
         self.write_tag(Tag::Dictionary)?;
         Ok(BinaryOrderWriter::new())
     }
-    fn end_set(&mut self, set: Self::SetWriter) -> IOResult<()> {
+    fn end_set(&mut self, set: Self::SetWriter) -> io::Result<()> {
         set.finish(self)
     }
 
-    fn start_embedded(&mut self) -> IOResult<Self::EmbeddedWriter> {
+    fn start_embedded(&mut self) -> io::Result<Self::EmbeddedWriter> {
         self.write_tag(Tag::Embedded)?;
         Ok(self.pop())
     }
-    fn end_embedded(&mut self, ptr: Self::EmbeddedWriter) -> IOResult<()> {
+    fn end_embedded(&mut self, ptr: Self::EmbeddedWriter) -> io::Result<()> {
         self.push(ptr);
         Ok(())
     }
@@ -308,54 +308,54 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
     type SetWriter = BinaryOrderWriter;
     type EmbeddedWriter = Self;
 
-    fn start_annotations(&mut self) -> IOResult<Self::AnnWriter> {
+    fn start_annotations(&mut self) -> io::Result<Self::AnnWriter> {
         Ok(self.suspend())
     }
 
-    fn end_annotations(&mut self, ann: Self::AnnWriter) -> IOResult<()> {
+    fn end_annotations(&mut self, ann: Self::AnnWriter) -> io::Result<()> {
         self.resume(ann);
         Ok(())
     }
 
-    fn align(&mut self, _natural_chunksize: u64) -> IOResult<()> {
+    fn align(&mut self, _natural_chunksize: u64) -> io::Result<()> {
         Ok(())
     }
 
-    fn write_bool(&mut self, v: bool) -> IOResult<()> {
+    fn write_bool(&mut self, v: bool) -> io::Result<()> {
         self.write_tag(if v { Tag::True } else { Tag::False })
     }
 
-    fn write_f32(&mut self, v: f32) -> IOResult<()> {
+    fn write_f32(&mut self, v: f32) -> io::Result<()> {
         self.write_tag(Tag::Float)?;
         self.write_raw_bytes(&u32::to_be_bytes(f32::to_bits(v)))
     }
 
-    fn write_f64(&mut self, v: f64) -> IOResult<()> {
+    fn write_f64(&mut self, v: f64) -> io::Result<()> {
         self.write_tag(Tag::Double)?;
         self.write_raw_bytes(&u64::to_be_bytes(f64::to_bits(v)))
     }
 
-    fn write_i8(&mut self, v: i8) -> IOResult<()> {
+    fn write_i8(&mut self, v: i8) -> io::Result<()> {
         if v >= -3 && v <= 12 { return self.write_tag(Tag::SmallInteger(v)) }
         self.write_medium_integer(&[v as u8])
     }
 
-    fn write_u8(&mut self, v: u8) -> IOResult<()> {
+    fn write_u8(&mut self, v: u8) -> io::Result<()> {
         if let Ok(w) = v.try_into() { return self.write_i8(w) }
         self.write_medium_integer(&[0, v])
     }
 
-    fn write_i16(&mut self, v: i16) -> IOResult<()> {
+    fn write_i16(&mut self, v: i16) -> io::Result<()> {
         if let Ok(w) = v.try_into() { return self.write_i8(w) }
         self.write_medium_integer(&[(v >> 8) as u8, (v & 255) as u8])
     }
 
-    fn write_u16(&mut self, v: u16) -> IOResult<()> {
+    fn write_u16(&mut self, v: u16) -> io::Result<()> {
         if let Ok(w) = v.try_into() { return self.write_i16(w) }
         self.write_medium_integer(&[0, (v >> 8) as u8, (v & 255) as u8])
     }
 
-    fn write_i32(&mut self, v: i32) -> IOResult<()> {
+    fn write_i32(&mut self, v: i32) -> io::Result<()> {
         if let Ok(w) = v.try_into() { return self.write_i16(w) }
         if fits_in_bytes!(v, 3) {
             return self.write_medium_integer(&[(v >> 16) as u8,
@@ -368,7 +368,7 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
                                     (v & 255) as u8])
     }
 
-    fn write_u32(&mut self, v: u32) -> IOResult<()> {
+    fn write_u32(&mut self, v: u32) -> io::Result<()> {
         if let Ok(w) = v.try_into() { return self.write_i32(w) }
         self.write_medium_integer(&[0,
                                     (v >> 24) as u8,
@@ -377,7 +377,7 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
                                     (v & 255) as u8])
     }
 
-    fn write_i64(&mut self, v: i64) -> IOResult<()> {
+    fn write_i64(&mut self, v: i64) -> io::Result<()> {
         if let Ok(w) = v.try_into() { return self.write_i32(w) }
         if fits_in_bytes!(v, 5) {
             return self.write_medium_integer(&[(v >> 32) as u8,
@@ -413,7 +413,7 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
                                     (v & 255) as u8])
     }
 
-    fn write_u64(&mut self, v: u64) -> IOResult<()> {
+    fn write_u64(&mut self, v: u64) -> io::Result<()> {
         if let Ok(w) = v.try_into() { return self.write_i64(w) }
         self.write_medium_integer(&[0,
                                     (v >> 56) as u8,
@@ -426,7 +426,7 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
                                     (v & 255) as u8])
     }
 
-    fn write_i128(&mut self, v: i128) -> IOResult<()> {
+    fn write_i128(&mut self, v: i128) -> io::Result<()> {
         if let Ok(w) = v.try_into() { return self.write_i64(w) }
         let bs: [u8; 16] = v.to_be_bytes();
         if fits_in_bytes!(v, 9)  { return self.write_medium_integer(&bs[7..]); }
@@ -439,7 +439,7 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
         self.write_medium_integer(&bs)
     }
 
-    fn write_u128(&mut self, v: u128) -> IOResult<()> {
+    fn write_u128(&mut self, v: u128) -> io::Result<()> {
         if let Ok(w) = v.try_into() { return self.write_i128(w) }
         let bs: [u8; 16] = v.to_be_bytes();
         self.write_tag(Tag::SignedInteger)?;
@@ -448,7 +448,7 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
         self.write_raw_bytes(&bs)
     }
 
-    fn write_int(&mut self, v: &BigInt) -> IOResult<()> {
+    fn write_int(&mut self, v: &BigInt) -> io::Result<()> {
         match v.to_i8() {
             Some(n) => self.write_i8(n),
             None => {
@@ -460,53 +460,53 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
         }
     }
 
-    fn write_string(&mut self, v: &str) -> IOResult<()> {
+    fn write_string(&mut self, v: &str) -> io::Result<()> {
         self.write_atom(Tag::String, v.as_bytes())
     }
 
-    fn write_bytes(&mut self, v: &[u8]) -> IOResult<()> {
+    fn write_bytes(&mut self, v: &[u8]) -> io::Result<()> {
         self.write_atom(Tag::ByteString, v)
     }
 
-    fn write_symbol(&mut self, v: &str) -> IOResult<()> {
+    fn write_symbol(&mut self, v: &str) -> io::Result<()> {
         self.write_atom(Tag::Symbol, v.as_bytes())
     }
 
-    fn start_record(&mut self, _field_count: Option<usize>) -> IOResult<Self::SeqWriter> {
+    fn start_record(&mut self, _field_count: Option<usize>) -> io::Result<Self::SeqWriter> {
         self.write_tag(Tag::Record)?;
         Ok(self.suspend())
     }
 
-    fn start_sequence(&mut self, _item_count: Option<usize>) -> IOResult<Self::SeqWriter> {
+    fn start_sequence(&mut self, _item_count: Option<usize>) -> io::Result<Self::SeqWriter> {
         self.write_tag(Tag::Sequence)?;
         Ok(self.suspend())
     }
 
-    fn end_seq(&mut self, seq: Self::SeqWriter) -> IOResult<()> {
+    fn end_seq(&mut self, seq: Self::SeqWriter) -> io::Result<()> {
         self.resume(seq);
         self.write_tag(Tag::End)
     }
 
-    fn start_set(&mut self, _item_count: Option<usize>) -> IOResult<Self::SetWriter> {
+    fn start_set(&mut self, _item_count: Option<usize>) -> io::Result<Self::SetWriter> {
         self.write_tag(Tag::Set)?;
         Ok(BinaryOrderWriter::new())
     }
 
-    fn start_dictionary(&mut self, _entry_count: Option<usize>) -> IOResult<Self::SetWriter> {
+    fn start_dictionary(&mut self, _entry_count: Option<usize>) -> io::Result<Self::SetWriter> {
         self.write_tag(Tag::Dictionary)?;
         Ok(BinaryOrderWriter::new())
     }
 
-    fn end_set(&mut self, set: Self::SetWriter) -> IOResult<()> {
+    fn end_set(&mut self, set: Self::SetWriter) -> io::Result<()> {
         set.finish(self)
     }
 
-    fn start_embedded(&mut self) -> IOResult<Self::EmbeddedWriter> {
+    fn start_embedded(&mut self) -> io::Result<Self::EmbeddedWriter> {
         self.write_tag(Tag::Embedded)?;
         Ok(self.suspend())
     }
 
-    fn end_embedded(&mut self, ann: Self::EmbeddedWriter) -> IOResult<()> {
+    fn end_embedded(&mut self, ann: Self::EmbeddedWriter) -> io::Result<()> {
         self.resume(ann);
         Ok(())
     }
diff --git a/implementations/rust/preserves/src/value/reader.rs b/implementations/rust/preserves/src/value/reader.rs
index 088f164..a15742e 100644
--- a/implementations/rust/preserves/src/value/reader.rs
+++ b/implementations/rust/preserves/src/value/reader.rs
@@ -1,15 +1,16 @@
 use crate::error::{self, ExpectedKind, Received, io_eof};
 
 use std::borrow::Cow;
+use std::io;
 use std::io::Read;
 use std::marker::PhantomData;
 
-use super::{DomainDecode, Embeddable, IOResult, IOValue, IOValueDomainCodec, NestedValue};
+use super::{DomainDecode, Embeddable, IOValue, IOValueDomainCodec, NestedValue};
 
 pub type ReaderResult<T> = std::result::Result<T, error::Error>;
 
 pub trait Reader<'de, D: Embeddable, N: NestedValue<D>> {
-    fn next(&mut self, read_annotations: bool) -> IOResult<Option<N>>;
+    fn next(&mut self, read_annotations: bool) -> io::Result<Option<N>>;
     fn open_record(&mut self, arity: Option<usize>) -> ReaderResult<()>;
     fn open_sequence_or_set(&mut self) -> ReaderResult<()>;
     fn open_sequence(&mut self) -> ReaderResult<()>;
@@ -21,13 +22,13 @@ pub trait Reader<'de, D: Embeddable, N: NestedValue<D>> {
 
     //---------------------------------------------------------------------------
 
-    fn skip_value(&mut self) -> IOResult<()> {
+    fn skip_value(&mut self) -> io::Result<()> {
         // TODO efficient skipping in specific impls of this trait
         let _ = self.demand_next(false)?;
         Ok(())
     }
 
-    fn demand_next(&mut self, read_annotations: bool) -> IOResult<N> {
+    fn demand_next(&mut self, read_annotations: bool) -> io::Result<N> {
         self.next(read_annotations)?.ok_or_else(io_eof)
     }
 
@@ -121,7 +122,7 @@ impl<'r, 'de, D: Embeddable, N: NestedValue<D>, R: Reader<'de, D, N>>
     Reader<'de, D, N>
     for &'r mut R
 {
-    fn next(&mut self, read_annotations: bool) -> IOResult<Option<N>> {
+    fn next(&mut self, read_annotations: bool) -> io::Result<Option<N>> {
         (*self).next(read_annotations)
     }
 
@@ -160,10 +161,10 @@ impl<'r, 'de, D: Embeddable, N: NestedValue<D>, R: Reader<'de, D, N>>
 
 
 pub trait BinarySource<'de>: Sized {
-    fn skip(&mut self) -> IOResult<()>;
-    fn peek(&mut self) -> IOResult<u8>;
-    fn readbytes(&mut self, count: usize) -> IOResult<Cow<'de, [u8]>>;
-    fn readbytes_into(&mut self, bs: &mut [u8]) -> IOResult<()>;
+    fn skip(&mut self) -> io::Result<()>;
+    fn peek(&mut self) -> io::Result<u8>;
+    fn readbytes(&mut self, count: usize) -> io::Result<Cow<'de, [u8]>>;
+    fn readbytes_into(&mut self, bs: &mut [u8]) -> io::Result<()>;
 
     fn packed<D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>>(
         &mut self,
@@ -191,13 +192,13 @@ impl<'a, R: Read> IOBinarySource<'a, R> {
 }
 
 impl<'de, 'a, R: Read> BinarySource<'de> for IOBinarySource<'a, R> {
-    fn skip(&mut self) -> IOResult<()> {
+    fn skip(&mut self) -> io::Result<()> {
         if self.buf.is_none() { unreachable!(); }
         self.buf = None;
         Ok(())
     }
 
-    fn peek(&mut self) -> IOResult<u8> {
+    fn peek(&mut self) -> io::Result<u8> {
         match self.buf {
             Some(b) => Ok(b),
             None => {
@@ -214,14 +215,14 @@ impl<'de, 'a, R: Read> BinarySource<'de> for IOBinarySource<'a, R> {
         }
     }
 
-    fn readbytes(&mut self, count: usize) -> IOResult<Cow<'de, [u8]>> {
+    fn readbytes(&mut self, count: usize) -> io::Result<Cow<'de, [u8]>> {
         if self.buf.is_some() { unreachable!(); }
         let mut bs = vec![0; count];
         self.read.read_exact(&mut bs)?;
         Ok(Cow::Owned(bs))
     }
 
-    fn readbytes_into(&mut self, bs: &mut [u8]) -> IOResult<()> {
+    fn readbytes_into(&mut self, bs: &mut [u8]) -> io::Result<()> {
         if self.buf.is_some() { unreachable!(); }
         self.read.read_exact(bs)
     }
@@ -239,13 +240,13 @@ impl<'de> BytesBinarySource<'de> {
 }
 
 impl<'de> BinarySource<'de> for BytesBinarySource<'de> {
-    fn skip(&mut self) -> IOResult<()> {
+    fn skip(&mut self) -> io::Result<()> {
         if self.index >= self.bytes.len() { unreachable!(); }
         self.index += 1;
         Ok(())
     }
 
-    fn peek(&mut self) -> IOResult<u8> {
+    fn peek(&mut self) -> io::Result<u8> {
         if self.index >= self.bytes.len() {
             Err(io_eof())
         } else {
@@ -253,7 +254,7 @@ impl<'de> BinarySource<'de> for BytesBinarySource<'de> {
         }
     }
 
-    fn readbytes(&mut self, count: usize) -> IOResult<Cow<'de, [u8]>> {
+    fn readbytes(&mut self, count: usize) -> io::Result<Cow<'de, [u8]>> {
         if self.index + count > self.bytes.len() {
             Err(io_eof())
         } else {
@@ -263,7 +264,7 @@ impl<'de> BinarySource<'de> for BytesBinarySource<'de> {
         }
     }
 
-    fn readbytes_into(&mut self, bs: &mut [u8]) -> IOResult<()> {
+    fn readbytes_into(&mut self, bs: &mut [u8]) -> io::Result<()> {
         let count = bs.len();
         if self.index + count > self.bytes.len() {
             Err(io_eof())
@@ -290,7 +291,7 @@ impl<'de, D: Embeddable, N: NestedValue<D>, R: Reader<'de, D, N>> ConfiguredRead
         self.read_annotations = read_annotations
     }
 
-    pub fn demand_next(&mut self) -> IOResult<N> {
+    pub fn demand_next(&mut self) -> io::Result<N> {
         self.reader.demand_next(self.read_annotations)
     }
 }
@@ -299,7 +300,7 @@ impl<'de, D: Embeddable, N: NestedValue<D>, R: Reader<'de, D, N>>
     std::iter::Iterator
     for ConfiguredReader<'de, D, N, R>
 {
-    type Item = IOResult<N>;
+    type Item = io::Result<N>;
     fn next(&mut self) -> Option<Self::Item> {
         match self.reader.next(self.read_annotations) {
             Err(e) => Some(Err(e)),
diff --git a/implementations/rust/preserves/src/value/writer.rs b/implementations/rust/preserves/src/value/writer.rs
index d90186b..df35de1 100644
--- a/implementations/rust/preserves/src/value/writer.rs
+++ b/implementations/rust/preserves/src/value/writer.rs
@@ -1,17 +1,17 @@
 use num::bigint::BigInt;
+use std::io;
 use super::DomainEncode;
-use super::IOResult;
 use super::signed_integer::SignedIntegerRepr;
 use super::repr::{Embeddable, Value, NestedValue, Float, Double};
 
 pub trait AnnotationWriter: Writer {
-    fn start_annotation(&mut self) -> IOResult<()>;
-    fn start_value(&mut self) -> IOResult<()>;
+    fn start_annotation(&mut self) -> io::Result<()>;
+    fn start_value(&mut self) -> io::Result<()>;
 }
 
 pub trait CompoundWriter: Writer {
-    fn extend(&mut self) -> IOResult<()>;
-    fn delimit(&mut self) -> IOResult<()>;
+    fn extend(&mut self) -> io::Result<()>;
+    fn delimit(&mut self) -> io::Result<()>;
 }
 
 pub trait Writer: Sized {
@@ -20,42 +20,42 @@ pub trait Writer: Sized {
     type SetWriter: CompoundWriter;
     type EmbeddedWriter: Writer;
 
-    fn align(&mut self, natural_chunksize: u64) -> IOResult<()>;
+    fn align(&mut self, natural_chunksize: u64) -> io::Result<()>;
 
-    fn start_annotations(&mut self) -> IOResult<Self::AnnWriter>;
-    fn end_annotations(&mut self, ann: Self::AnnWriter) -> IOResult<()>;
+    fn start_annotations(&mut self) -> io::Result<Self::AnnWriter>;
+    fn end_annotations(&mut self, ann: Self::AnnWriter) -> io::Result<()>;
 
-    fn write_bool(&mut self, v: bool) -> IOResult<()>;
+    fn write_bool(&mut self, v: bool) -> io::Result<()>;
 
-    fn write_f32(&mut self, v: f32) -> IOResult<()>;
-    fn write_f64(&mut self, v: f64) -> IOResult<()>;
+    fn write_f32(&mut self, v: f32) -> io::Result<()>;
+    fn write_f64(&mut self, v: f64) -> io::Result<()>;
 
-    fn write_i8(&mut self, v: i8) -> IOResult<()>;
-    fn write_u8(&mut self, v: u8) -> IOResult<()>;
-    fn write_i16(&mut self, v: i16) -> IOResult<()>;
-    fn write_u16(&mut self, v: u16) -> IOResult<()>;
-    fn write_i32(&mut self, v: i32) -> IOResult<()>;
-    fn write_u32(&mut self, v: u32) -> IOResult<()>;
-    fn write_i64(&mut self, v: i64) -> IOResult<()>;
-    fn write_u64(&mut self, v: u64) -> IOResult<()>;
-    fn write_i128(&mut self, v: i128) -> IOResult<()>;
-    fn write_u128(&mut self, v: u128) -> IOResult<()>;
-    fn write_int(&mut self, v: &BigInt) -> IOResult<()>;
+    fn write_i8(&mut self, v: i8) -> io::Result<()>;
+    fn write_u8(&mut self, v: u8) -> io::Result<()>;
+    fn write_i16(&mut self, v: i16) -> io::Result<()>;
+    fn write_u16(&mut self, v: u16) -> io::Result<()>;
+    fn write_i32(&mut self, v: i32) -> io::Result<()>;
+    fn write_u32(&mut self, v: u32) -> io::Result<()>;
+    fn write_i64(&mut self, v: i64) -> io::Result<()>;
+    fn write_u64(&mut self, v: u64) -> io::Result<()>;
+    fn write_i128(&mut self, v: i128) -> io::Result<()>;
+    fn write_u128(&mut self, v: u128) -> io::Result<()>;
+    fn write_int(&mut self, v: &BigInt) -> io::Result<()>;
 
-    fn write_string(&mut self, v: &str) -> IOResult<()>;
-    fn write_bytes(&mut self, v: &[u8]) -> IOResult<()>;
-    fn write_symbol(&mut self, v: &str) -> IOResult<()>;
+    fn write_string(&mut self, v: &str) -> io::Result<()>;
+    fn write_bytes(&mut self, v: &[u8]) -> io::Result<()>;
+    fn write_symbol(&mut self, v: &str) -> io::Result<()>;
 
-    fn start_record(&mut self, field_count: Option<usize>) -> IOResult<Self::SeqWriter>;
-    fn start_sequence(&mut self, item_count: Option<usize>) -> IOResult<Self::SeqWriter>;
-    fn end_seq(&mut self, seq: Self::SeqWriter) -> IOResult<()>;
+    fn start_record(&mut self, field_count: Option<usize>) -> io::Result<Self::SeqWriter>;
+    fn start_sequence(&mut self, item_count: Option<usize>) -> io::Result<Self::SeqWriter>;
+    fn end_seq(&mut self, seq: Self::SeqWriter) -> io::Result<()>;
 
-    fn start_set(&mut self, item_count: Option<usize>) -> IOResult<Self::SetWriter>;
-    fn start_dictionary(&mut self, entry_count: Option<usize>) -> IOResult<Self::SetWriter>;
-    fn end_set(&mut self, set: Self::SetWriter) -> IOResult<()>;
+    fn start_set(&mut self, item_count: Option<usize>) -> io::Result<Self::SetWriter>;
+    fn start_dictionary(&mut self, entry_count: Option<usize>) -> io::Result<Self::SetWriter>;
+    fn end_set(&mut self, set: Self::SetWriter) -> io::Result<()>;
 
-    fn start_embedded(&mut self) -> IOResult<Self::EmbeddedWriter>;
-    fn end_embedded(&mut self, ptr: Self::EmbeddedWriter) -> IOResult<()>;
+    fn start_embedded(&mut self) -> io::Result<Self::EmbeddedWriter>;
+    fn end_embedded(&mut self, ptr: Self::EmbeddedWriter) -> io::Result<()>;
 
     //---------------------------------------------------------------------------
 
@@ -63,7 +63,7 @@ pub trait Writer: Sized {
         &mut self,
         enc: &mut Enc,
         v: &N,
-    ) -> IOResult<()> {
+    ) -> io::Result<()> {
         match v.annotations().maybe_slice() {
             None => {
                 self.write_value(enc, v.value())?;
@@ -86,7 +86,7 @@ pub trait Writer: Sized {
         &mut self,
         enc: &mut Enc,
         v: &Value<N, D>,
-    ) -> IOResult<()> {
+    ) -> io::Result<()> {
         match v {
             Value::Boolean(b) => self.write_bool(*b),
             Value::Float(Float(f)) => self.write_f32(*f),
@@ -148,7 +148,7 @@ pub trait Writer: Sized {
     }
 }
 
-pub fn varint<W: std::io::Write>(w: &mut W, mut v: u64) -> IOResult<usize> {
+pub fn varint<W: std::io::Write>(w: &mut W, mut v: u64) -> io::Result<usize> {
     let mut byte_count = 0;
     loop {
         byte_count += 1;