openpgp: Use non_exhaustive attribute.

  - Fixes #563
  - With an MSRV >= 1.40.0, we can use #[non_exhaustive], as mentioned
    in #406.
  - This is also a clippy lint:
    https://rust-lang.github.io/rust-clippy/master/index.html#manual_non_exhaustive

1 files changed, 1 insertions, 5 deletions

diff --git a/openpgp/src/message/mod.rs b/openpgp/src/message/mod.rs
index 82dd1695..5b35f161 100644
--- a/openpgp/src/message/mod.rs
+++ b/openpgp/src/message/mod.rs
@@ -48,16 +48,13 @@ use self::grammar::MessageParser;
 ///
 /// Note: This enum cannot be exhaustively matched to allow future
 /// extensions.
+#[non_exhaustive]
 #[derive(Debug, Clone)]
 pub enum MessageParserError {
     /// A parser error.
     Parser(ParseError<usize, Token, LexicalError>),
     /// An OpenPGP error.
     OpenPGP(Error),
-
-    /// This marks this enum as non-exhaustive.  Do not use this
-    /// variant.
-    #[doc(hidden)] __Nonexhaustive,
 }
 
 impl From<MessageParserError> for anyhow::Error {
@@ -65,7 +62,6 @@ impl From<MessageParserError> for anyhow::Error {
         match err {
             MessageParserError::Parser(p) => p.into(),
             MessageParserError::OpenPGP(p) => p.into(),
-            MessageParserError::__Nonexhaustive => unreachable!(),
         }
     }
 }