Fix rustc build

PR  #199

Author: GuillaumeGomez

CHANGELOG.md

@@ -5,6 +5,7 @@
 - [Add a new method for `Error`: `chain_err`.](https://github.com/brson/error-chain/pull/141)
 - [Allow `chain_err` to be used on `Option<T>`](https://github.com/brson/error-chain/pull/156)
 - [Add support for creating an error chain on boxed trait errors (`Box<Error>`)](https://github.com/brson/error-chain/pull/156)
+- [Remove lint for unused doc comment.](https://github.com/brson/error-chain/pull/199)
 
 # 0.10.0
 

src/error_chain.rs

@@ -172,6 +172,7 @@ macro_rules! error_chain_processed {
                 self.0.description()
             }
 
+            #[allow(unused_doc_comment)]
             fn cause(&self) -> Option<&::std::error::Error> {
                 match self.1.next_error {
                     Some(ref c) => Some(&**c),
@@ -423,6 +424,7 @@ macro_rules! impl_extract_backtrace {
     ($error_name: ident
      $error_kind_name: ident
      $([$link_error_path: path, $(#[$meta_links: meta])*])*) => {
+        #[allow(unused_doc_comment)]
         fn extract_backtrace(e: &(::std::error::Error + Send + 'static))
             -> Option<::std::sync::Arc<$crate::Backtrace>> {
             if let Some(e) = e.downcast_ref::<$error_name>() {

src/quick_error.rs

@@ -260,7 +260,7 @@ macro_rules! quick_error {
             $item:ident: $imode:tt [$(#[$imeta:meta])*] [$( $var:ident: $typ:ty ),*] {$( $funcs:tt )*}
         )*}
     ) => {
-        #[allow(unused)]
+        #[allow(unused, unused_doc_comment)]
         impl ::std::fmt::Display for $name {
             fn fmt(&self, fmt: &mut ::std::fmt::Formatter)
                 -> ::std::fmt::Result
@@ -310,7 +310,7 @@ macro_rules! quick_error {
                 }
             }
         }*/
-        #[allow(unused)]
+        #[allow(unused, unused_doc_comment)]
         impl $name {
             /// A string describing the error kind.
             pub fn description(&self) -> &str {