openpgp: Clarify that message::Token is not covered by SemVer.

  - Do this using a deprecation so that anyone using it will get a
    compiler warning.

  - Revert this change once message::Token is private.

  - See #836.

2 files changed, 6 insertions, 1 deletions

diff --git a/openpgp/src/message/lexer.rs b/openpgp/src/message/lexer.rs
index 8e6f8910..e32f58ed 100644
--- a/openpgp/src/message/lexer.rs
+++ b/openpgp/src/message/lexer.rs
@@ -13,6 +13,8 @@ pub(crate) type LexerItem<Tok, Loc, Error>
 /// extensions.
 #[non_exhaustive]
 #[derive(Debug, Clone, Copy, PartialEq)]
+#[deprecated(since = "1.9.0",
+             note = "Not covered by SemVer guarantees, DO NOT match on it.")]
 pub enum Token {
     /// A Literal data packet.
     Literal,
diff --git a/openpgp/src/message/mod.rs b/openpgp/src/message/mod.rs
index 0967607e..9e734aa4 100644
--- a/openpgp/src/message/mod.rs
+++ b/openpgp/src/message/mod.rs
@@ -21,6 +21,9 @@
 //!
 //! [Section 11.3 of RFC 4880]: https://tools.ietf.org/html/rfc4880#section-11.3
 
+// XXX: For Token.  Drop this once Token is private.
+#![allow(deprecated)]
+
 use std::convert::TryFrom;
 use std::fmt;
 use std::io;
@@ -35,7 +38,7 @@ use crate::packet::Tag;
 use crate::parse::Parse;
 
 mod lexer;
-lalrpop_util::lalrpop_mod!(#[allow(clippy::all)] grammar, "/message/grammar.rs");
+lalrpop_util::lalrpop_mod!(#[allow(clippy::all, deprecated)] grammar, "/message/grammar.rs");
 
 use self::lexer::{Lexer, LexicalError};
 pub use self::lexer::Token;