#display #derive

macro displaydoc-watt

A derive macro for implementing the display Trait via a doc comment and string interpolation

1 unstable release

0.1.0 Nov 21, 2019

#1853 in Procedural macros


293 lines

derive(Display) /// From<docs>

Latest Version Rust Documentation

This library provides a convenient derive macro for the standard library's core::fmt::Display trait.

displaydoc-watt = "0.1"

Compiler support: requires rustc 1.34+


use displaydoc_watt::Display;
use thiserror::Error;

#[derive(Display, Error, Debug)]
pub enum DataStoreError {
    /// data store disconnected
    Disconnect(#[source] io::Error),
    /// the data for key `{0}` is not available
    /// invalid header (expected {expected:?}, found {found:?})
    InvalidHeader {
        expected: String,
        found: String,
    /// unknown data store error


  • A Display impl is generated for your type if you provide doc comment messages on the struct or each variant of your enum, as shown above in the example.

    The messages support a shorthand for interpolating fields from the error.

    • /// {var}write!("{}", self.var)
    • /// {0}write!("{}", self.0)
    • /// {var:?}write!("{:?}", self.var)
    • /// {0:?}write!("{:?}", self.0)


  1. Is this crate no_std compatible?

    • Not at the moment, the primary displaydoc crate does support no_std but I have not yet figured out how to make that work when the proc macro is compiled to wasm.
  2. Does this crate work with Path and PathBuf via the Display trait?

    • Yuuup. This crate uses @dtolnay's autoref specialization technique to add a special trait for types to get the display impl, it then specializes for Path and PathBuf and when either of these types are found it calls self.display() to get a std::path::Display<'_> type which can be used with the Display format specifier!


Licensed under either of Apache License, Version 2.0 or MIT license at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.