gnu: emacs-rust-mode: Update to 0.4.0.

* gnu/packages/emacs-xyz.scm (emacs-rust-mode): Update to 0.4.0.

Signed-off-by: Brian Leung <leungbk@mailfence.com>

gnu/packages/emacs-xyz.scm

@@ -15066,24 +15066,18 @@ files.  It focuses on highlighting the document to improve readability.")
     (license license:gpl2+)))
 
 (define-public emacs-rust-mode
-  (let ((commit
-         ;; Last release is old (2016), use more recent commit to get bug
-         ;; fixes.
-         "64b4a2450e4d4c47f6307851c9b2598cd2254d68")
-        (revision "0"))
   (package
     (name "emacs-rust-mode")
-      (version (git-version "0.3.0" revision commit))
+    (version "0.4.0")
     (source (origin
               (method git-fetch)
-                (uri
+              (uri (git-reference
-                 (git-reference
                     (url "https://github.com/rust-lang/rust-mode")
-                  (commit commit)))
+                    (commit version)))
               (file-name (git-file-name name version))
               (sha256
                (base32
-                  "0pbz36lljgb7bdgx3h3g0pq1nss1kvn8mhk1l3mknsmynd6w4nd8"))))
+                "0bcrklyicxh032rrp585rl5mxd26nb61dp6r5bl935rlcmxzsczh"))))
     (build-system emacs-build-system)
     (arguments
      `(#:phases
@@ -15096,7 +15090,7 @@ files.  It focuses on highlighting the document to improve readability.")
     (description "This package provides a major Emacs mode for editing Rust
 source code.")
     (license (list license:expat
-                     license:asl2.0)))))
+                   license:asl2.0))))
 
 (define-public emacs-ztree
   (let ((commit "c54425a094353ec40a8179f9eab3596f76c6cf94"))