From 1b8cf2705e277219d093b5820e39f84cd7834af1 Mon Sep 17 00:00:00 2001
From: Sergey Pepyakin <sergei@parity.io>
Date: Fri, 25 Jan 2019 11:39:59 +0100
Subject: [PATCH] Add docs.

---
 derive/src/lib.rs | 42 ++++++++++++++++++++++++++++++++++++++++++
 src/host.rs       |  2 ++
 tests/derives.rs  |  2 ++
 3 files changed, 46 insertions(+)

diff --git a/derive/src/lib.rs b/derive/src/lib.rs
index c119dbc..cd5605f 100644
--- a/derive/src/lib.rs
+++ b/derive/src/lib.rs
@@ -1,3 +1,45 @@
+//! A derive macro for generation of simple `Externals`.
+//!
+//! ```nocompile
+//! #// no compile because we can't depend on wasmi here, or otherwise it will be a circular dependency.
+//! extern crate wasmi;
+//! extern crate wasmi_derive;
+//!
+//! use std::fmt;
+//! use wasmi::HostError;
+//! use wasmi_derive::derive_externals;
+//!
+//! #[derive(Debug)]
+//! struct NoInfoError;
+//! impl HostError for NoInfoError {}
+//! impl fmt::Display for NoInfoError {
+//!     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+//!         write!(f, "NoInfoError")
+//!     }
+//! }
+//!
+//! struct NonStaticExternals<'a> {
+//!     state: &'a mut usize,
+//! }
+//!
+//! #[derive_externals]
+//! impl<'a> NonStaticExternals<'a> {
+//!     pub fn hello(&self, a: u32, b: u32) -> u32 {
+//!         a + b
+//!     }
+//!
+//!     pub fn increment(&mut self) {
+//!         *self.state += 1;
+//!     }
+//!
+//!     pub fn traps(&self) -> Result<(), NoInfoError> {
+//!         Err(NoInfoError)
+//!     }
+//! }
+//! ```
+//!
+
+// We reached the `recursion_limit` in quote macro.
 #![recursion_limit = "128"]
 
 extern crate proc_macro;
diff --git a/src/host.rs b/src/host.rs
index 3700fc7..e215a2f 100644
--- a/src/host.rs
+++ b/src/host.rs
@@ -137,6 +137,8 @@ impl HostError {
 
 /// Trait that allows to implement host functions.
 ///
+/// You can use `wasmi-derive` or you can implement this trait manually.
+///
 /// # Examples
 ///
 /// ```rust
diff --git a/tests/derives.rs b/tests/derives.rs
index 1d93fcd..2f05f24 100644
--- a/tests/derives.rs
+++ b/tests/derives.rs
@@ -1,3 +1,5 @@
+// If you are to update this code, make sure you update the example in `wasmi-derive`.
+
 extern crate wasmi;
 extern crate wasmi_derive;