diff --git a/artiq/runtime.rs/libstd_artiq/error.rs b/artiq/runtime.rs/libstd_artiq/error.rs
new file mode 100644
index 000000000..df1d76b6c
--- /dev/null
+++ b/artiq/runtime.rs/libstd_artiq/error.rs
@@ -0,0 +1,453 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Traits for working with Errors.
+//!
+//! # The `Error` trait
+//!
+//! `Error` is a trait representing the basic expectations for error values,
+//! i.e. values of type `E` in `Result<T, E>`. At a minimum, errors must provide
+//! a description, but they may optionally provide additional detail (via
+//! `Display`) and cause chain information:
+//!
+//! ```
+//! use std::fmt::Display;
+//!
+//! trait Error: Display {
+//!     fn description(&self) -> &str;
+//!
+//!     fn cause(&self) -> Option<&Error> { None }
+//! }
+//! ```
+//!
+//! The `cause` method is generally used when errors cross "abstraction
+//! boundaries", i.e.  when a one module must report an error that is "caused"
+//! by an error from a lower-level module. This setup makes it possible for the
+//! high-level module to provide its own errors that do not commit to any
+//! particular implementation, but also reveal some of its implementation for
+//! debugging via `cause` chains.
+
+// A note about crates and the facade:
+//
+// Originally, the `Error` trait was defined in libcore, and the impls
+// were scattered about. However, coherence objected to this
+// arrangement, because to create the blanket impls for `Box` required
+// knowing that `&str: !Error`, and we have no means to deal with that
+// sort of conflict just now. Therefore, for the time being, we have
+// moved the `Error` trait into libstd. As we evolve a sol'n to the
+// coherence challenge (e.g., specialization, neg impls, etc) we can
+// reconsider what crate these items belong in.
+
+use any::TypeId;
+use boxed::Box;
+use cell;
+use fmt::{self, Debug, Display};
+use marker::{Send, Sync, Reflect};
+use mem::transmute;
+use num;
+use core::raw::TraitObject;
+use str;
+use string::{self, String};
+
+/// Base functionality for all errors in Rust.
+pub trait Error: Debug + Display + Reflect {
+    /// A short description of the error.
+    ///
+    /// The description should not contain newlines or sentence-ending
+    /// punctuation, to facilitate embedding in larger user-facing
+    /// strings.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::error::Error;
+    ///
+    /// match "xc".parse::<u32>() {
+    ///     Err(e) => {
+    ///         println!("Error: {}", e.description());
+    ///     }
+    ///     _ => println!("No error"),
+    /// }
+    /// ```
+    fn description(&self) -> &str;
+
+    /// The lower-level cause of this error, if any.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::error::Error;
+    /// use std::fmt;
+    ///
+    /// #[derive(Debug)]
+    /// struct SuperError {
+    ///     side: SuperErrorSideKick,
+    /// }
+    ///
+    /// impl fmt::Display for SuperError {
+    ///     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    ///         write!(f, "SuperError is here!")
+    ///     }
+    /// }
+    ///
+    /// impl Error for SuperError {
+    ///     fn description(&self) -> &str {
+    ///         "I'm the superhero of errors!"
+    ///     }
+    ///
+    ///     fn cause(&self) -> Option<&Error> {
+    ///         Some(&self.side)
+    ///     }
+    /// }
+    ///
+    /// #[derive(Debug)]
+    /// struct SuperErrorSideKick;
+    ///
+    /// impl fmt::Display for SuperErrorSideKick {
+    ///     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    ///         write!(f, "SuperErrorSideKick is here!")
+    ///     }
+    /// }
+    ///
+    /// impl Error for SuperErrorSideKick {
+    ///     fn description(&self) -> &str {
+    ///         "I'm SuperError side kick!"
+    ///     }
+    /// }
+    ///
+    /// fn get_super_error() -> Result<(), SuperError> {
+    ///     Err(SuperError { side: SuperErrorSideKick })
+    /// }
+    ///
+    /// fn main() {
+    ///     match get_super_error() {
+    ///         Err(e) => {
+    ///             println!("Error: {}", e.description());
+    ///             println!("Caused by: {}", e.cause().unwrap());
+    ///         }
+    ///         _ => println!("No error"),
+    ///     }
+    /// }
+    /// ```
+    fn cause(&self) -> Option<&Error> { None }
+
+    /// Get the `TypeId` of `self`
+    #[doc(hidden)]
+    fn type_id(&self) -> TypeId where Self: 'static {
+        TypeId::of::<Self>()
+    }
+}
+
+impl<'a, E: Error + 'a> From<E> for Box<Error + 'a> {
+    fn from(err: E) -> Box<Error + 'a> {
+        Box::new(err)
+    }
+}
+
+impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<Error + Send + Sync + 'a> {
+    fn from(err: E) -> Box<Error + Send + Sync + 'a> {
+        Box::new(err)
+    }
+}
+
+impl From<String> for Box<Error + Send + Sync> {
+    fn from(err: String) -> Box<Error + Send + Sync> {
+        #[derive(Debug)]
+        struct StringError(String);
+
+        impl Error for StringError {
+            fn description(&self) -> &str { &self.0 }
+        }
+
+        impl Display for StringError {
+            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                Display::fmt(&self.0, f)
+            }
+        }
+
+        Box::new(StringError(err))
+    }
+}
+
+impl From<String> for Box<Error> {
+    fn from(str_err: String) -> Box<Error> {
+        let err1: Box<Error + Send + Sync> = From::from(str_err);
+        let err2: Box<Error> = err1;
+        err2
+    }
+}
+
+impl<'a, 'b> From<&'b str> for Box<Error + Send + Sync + 'a> {
+    fn from(err: &'b str) -> Box<Error + Send + Sync + 'a> {
+        From::from(String::from(err))
+    }
+}
+
+impl<'a> From<&'a str> for Box<Error> {
+    fn from(err: &'a str) -> Box<Error> {
+        From::from(String::from(err))
+    }
+}
+
+impl Error for str::ParseBoolError {
+    fn description(&self) -> &str { "failed to parse bool" }
+}
+
+impl Error for str::Utf8Error {
+    fn description(&self) -> &str {
+        "invalid utf-8: corrupt contents"
+    }
+}
+
+impl Error for num::ParseIntError {
+    fn description(&self) -> &str {
+        self.__description()
+    }
+}
+
+impl Error for num::TryFromIntError {
+    fn description(&self) -> &str {
+        self.__description()
+    }
+}
+
+impl Error for num::ParseFloatError {
+    fn description(&self) -> &str {
+        self.__description()
+    }
+}
+
+impl Error for string::FromUtf8Error {
+    fn description(&self) -> &str {
+        "invalid utf-8"
+    }
+}
+
+impl Error for string::FromUtf16Error {
+    fn description(&self) -> &str {
+        "invalid utf-16"
+    }
+}
+
+impl Error for string::ParseError {
+    fn description(&self) -> &str {
+        match *self {}
+    }
+}
+
+impl<T: Error> Error for Box<T> {
+    fn description(&self) -> &str {
+        Error::description(&**self)
+    }
+
+    fn cause(&self) -> Option<&Error> {
+        Error::cause(&**self)
+    }
+}
+
+impl Error for fmt::Error {
+    fn description(&self) -> &str {
+        "an error occurred when formatting an argument"
+    }
+}
+
+impl<'a, T: ?Sized + Reflect> Error for cell::BorrowError<'a, T> {
+    fn description(&self) -> &str {
+        "already mutably borrowed"
+    }
+}
+
+impl<'a, T: ?Sized + Reflect> Error for cell::BorrowMutError<'a, T> {
+    fn description(&self) -> &str {
+        "already borrowed"
+    }
+}
+
+// copied from any.rs
+impl Error + 'static {
+    /// Returns true if the boxed type is the same as `T`
+    #[inline]
+    pub fn is<T: Error + 'static>(&self) -> bool {
+        // Get TypeId of the type this function is instantiated with
+        let t = TypeId::of::<T>();
+
+        // Get TypeId of the type in the trait object
+        let boxed = self.type_id();
+
+        // Compare both TypeIds on equality
+        t == boxed
+    }
+
+    /// Returns some reference to the boxed value if it is of type `T`, or
+    /// `None` if it isn't.
+    #[inline]
+    pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T> {
+        if self.is::<T>() {
+            unsafe {
+                // Get the raw representation of the trait object
+                let to: TraitObject = transmute(self);
+
+                // Extract the data pointer
+                Some(&*(to.data as *const T))
+            }
+        } else {
+            None
+        }
+    }
+
+    /// Returns some mutable reference to the boxed value if it is of type `T`, or
+    /// `None` if it isn't.
+    #[inline]
+    pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T> {
+        if self.is::<T>() {
+            unsafe {
+                // Get the raw representation of the trait object
+                let to: TraitObject = transmute(self);
+
+                // Extract the data pointer
+                Some(&mut *(to.data as *const T as *mut T))
+            }
+        } else {
+            None
+        }
+    }
+}
+
+impl Error + 'static + Send {
+    /// Forwards to the method defined on the type `Any`.
+    #[inline]
+    pub fn is<T: Error + 'static>(&self) -> bool {
+        <Error + 'static>::is::<T>(self)
+    }
+
+    /// Forwards to the method defined on the type `Any`.
+    #[inline]
+    pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T> {
+        <Error + 'static>::downcast_ref::<T>(self)
+    }
+
+    /// Forwards to the method defined on the type `Any`.
+    #[inline]
+    pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T> {
+        <Error + 'static>::downcast_mut::<T>(self)
+    }
+}
+
+impl Error + 'static + Send + Sync {
+    /// Forwards to the method defined on the type `Any`.
+    #[inline]
+    pub fn is<T: Error + 'static>(&self) -> bool {
+        <Error + 'static>::is::<T>(self)
+    }
+
+    /// Forwards to the method defined on the type `Any`.
+    #[inline]
+    pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T> {
+        <Error + 'static>::downcast_ref::<T>(self)
+    }
+
+    /// Forwards to the method defined on the type `Any`.
+    #[inline]
+    pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T> {
+        <Error + 'static>::downcast_mut::<T>(self)
+    }
+}
+
+impl Error {
+    #[inline]
+    /// Attempt to downcast the box to a concrete type.
+    pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<Error>> {
+        if self.is::<T>() {
+            unsafe {
+                // Get the raw representation of the trait object
+                let raw = Box::into_raw(self);
+                let to: TraitObject =
+                    transmute::<*mut Error, TraitObject>(raw);
+
+                // Extract the data pointer
+                Ok(Box::from_raw(to.data as *mut T))
+            }
+        } else {
+            Err(self)
+        }
+    }
+}
+
+impl Error + Send {
+    #[inline]
+    /// Attempt to downcast the box to a concrete type.
+    pub fn downcast<T: Error + 'static>(self: Box<Self>)
+                                        -> Result<Box<T>, Box<Error + Send>> {
+        let err: Box<Error> = self;
+        <Error>::downcast(err).map_err(|s| unsafe {
+            // reapply the Send marker
+            transmute::<Box<Error>, Box<Error + Send>>(s)
+        })
+    }
+}
+
+impl Error + Send + Sync {
+    #[inline]
+    /// Attempt to downcast the box to a concrete type.
+    pub fn downcast<T: Error + 'static>(self: Box<Self>)
+                                        -> Result<Box<T>, Box<Self>> {
+        let err: Box<Error> = self;
+        <Error>::downcast(err).map_err(|s| unsafe {
+            // reapply the Send+Sync marker
+            transmute::<Box<Error>, Box<Error + Send + Sync>>(s)
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use prelude::v1::*;
+    use super::Error;
+    use fmt;
+
+    #[derive(Debug, PartialEq)]
+    struct A;
+    #[derive(Debug, PartialEq)]
+    struct B;
+
+    impl fmt::Display for A {
+        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+            write!(f, "A")
+        }
+    }
+    impl fmt::Display for B {
+        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+            write!(f, "B")
+        }
+    }
+
+    impl Error for A {
+        fn description(&self) -> &str { "A-desc" }
+    }
+    impl Error for B {
+        fn description(&self) -> &str { "A-desc" }
+    }
+
+    #[test]
+    fn downcasting() {
+        let mut a = A;
+        let mut a = &mut a as &mut (Error + 'static);
+        assert_eq!(a.downcast_ref::<A>(), Some(&A));
+        assert_eq!(a.downcast_ref::<B>(), None);
+        assert_eq!(a.downcast_mut::<A>(), Some(&mut A));
+        assert_eq!(a.downcast_mut::<B>(), None);
+
+        let a: Box<Error> = Box::new(A);
+        match a.downcast::<B>() {
+            Ok(..) => panic!("expected error"),
+            Err(e) => assert_eq!(*e.downcast::<A>().unwrap(), A),
+        }
+    }
+}
diff --git a/artiq/runtime.rs/libstd_artiq/io/error.rs b/artiq/runtime.rs/libstd_artiq/io/error.rs
index bdb040c03..f8684a4ec 100644
--- a/artiq/runtime.rs/libstd_artiq/io/error.rs
+++ b/artiq/runtime.rs/libstd_artiq/io/error.rs
@@ -14,7 +14,7 @@ use core::fmt;
 use core::marker::{Send, Sync};
 use core::option::Option::{self, Some, None};
 use core::result;
- use collections::string::String;
+use error;
 
 /// A specialized [`Result`](../result/enum.Result.html) type for I/O
 /// operations.
@@ -68,7 +68,7 @@ enum Repr {
 #[derive(Debug)]
 struct Custom {
     kind: ErrorKind,
-    error: String,
+    error: Box<error::Error+Send+Sync>,
 }
 
 /// A list specifying general categories of I/O error.
@@ -163,12 +163,12 @@ impl Error {
     /// let custom_error2 = Error::new(ErrorKind::Interrupted, custom_error);
     /// ```
     pub fn new<E>(kind: ErrorKind, error: E) -> Error
-        where E: Into<String>
+        where E: Into<Box<error::Error+Send+Sync>>
     {
         Self::_new(kind, error.into())
     }
 
-    fn _new(kind: ErrorKind, error: String) -> Error {
+    fn _new(kind: ErrorKind, error: Box<error::Error+Send+Sync>) -> Error {
         Error {
             repr: Repr::Custom(Box::new(Custom {
                 kind: kind,
@@ -198,10 +198,10 @@ impl Error {
     ///
     /// If this `Error` was constructed via `new` then this function will
     /// return `Some`, otherwise it will return `None`.
-    pub fn get_ref(&self) -> Option<&String> {
+    pub fn get_ref(&self) -> Option<&(error::Error+Send+Sync+'static)> {
         match self.repr {
             Repr::Os(..) => None,
-            Repr::Custom(ref c) => Some(&c.error),
+            Repr::Custom(ref c) => Some(&*c.error),
         }
     }
 
@@ -210,10 +210,10 @@ impl Error {
     ///
     /// If this `Error` was constructed via `new` then this function will
     /// return `Some`, otherwise it will return `None`.
-    pub fn get_mut(&mut self) -> Option<&mut String> {
+    pub fn get_mut(&mut self) -> Option<&mut (error::Error+Send+Sync+'static)> {
         match self.repr {
             Repr::Os(..) => None,
-            Repr::Custom(ref mut c) => Some(&mut c.error),
+            Repr::Custom(ref mut c) => Some(&mut *c.error),
         }
     }
 
@@ -221,7 +221,7 @@ impl Error {
     ///
     /// If this `Error` was constructed via `new` then this function will
     /// return `Some`, otherwise it will return `None`.
-    pub fn into_inner(self) -> Option<String> {
+    pub fn into_inner(self) -> Option<Box<error::Error+Send+Sync>> {
         match self.repr {
             Repr::Os(..) => None,
             Repr::Custom(c) => Some(c.error)
@@ -258,6 +258,42 @@ impl fmt::Display for Error {
     }
 }
 
+impl error::Error for Error {
+    fn description(&self) -> &str {
+        match self.repr {
+            Repr::Os(..) => match self.kind() {
+                ErrorKind::NotFound => "entity not found",
+                ErrorKind::PermissionDenied => "permission denied",
+                ErrorKind::ConnectionRefused => "connection refused",
+                ErrorKind::ConnectionReset => "connection reset",
+                ErrorKind::ConnectionAborted => "connection aborted",
+                ErrorKind::NotConnected => "not connected",
+                ErrorKind::AddrInUse => "address in use",
+                ErrorKind::AddrNotAvailable => "address not available",
+                ErrorKind::BrokenPipe => "broken pipe",
+                ErrorKind::AlreadyExists => "entity already exists",
+                ErrorKind::WouldBlock => "operation would block",
+                ErrorKind::InvalidInput => "invalid input parameter",
+                ErrorKind::InvalidData => "invalid data",
+                ErrorKind::TimedOut => "timed out",
+                ErrorKind::WriteZero => "write zero",
+                ErrorKind::Interrupted => "operation interrupted",
+                ErrorKind::Other => "other os error",
+                ErrorKind::UnexpectedEof => "unexpected end of file",
+                ErrorKind::__Nonexhaustive => unreachable!()
+            },
+            Repr::Custom(ref c) => c.error.description(),
+        }
+    }
+
+    fn cause(&self) -> Option<&error::Error> {
+        match self.repr {
+            Repr::Os(..) => None,
+            Repr::Custom(ref c) => c.error.cause(),
+        }
+    }
+}
+
 fn _assert_error_is_sync_send() {
     fn _is_sync_send<T: Sync+Send>() {}
     _is_sync_send::<Error>();
diff --git a/artiq/runtime.rs/libstd_artiq/lib.rs b/artiq/runtime.rs/libstd_artiq/lib.rs
index 5c4abf384..1ec357302 100644
--- a/artiq/runtime.rs/libstd_artiq/lib.rs
+++ b/artiq/runtime.rs/libstd_artiq/lib.rs
@@ -1,5 +1,6 @@
 #![feature(lang_items, asm, alloc, collections, libc, needs_panic_runtime,
-           question_mark, unicode)]
+           question_mark, unicode, reflect_marker, raw, int_error_internals,
+           try_from, try_borrow)]
 #![no_std]
 #![needs_panic_runtime]
 
@@ -27,6 +28,7 @@ pub mod prelude {
 }
 
 pub mod time;
+pub mod error;
 pub mod io;
 
 use core::fmt::Write;