Do not allow !=

Only allow <> and suggest this operator when != is used

Signed-off-by: Rudi Grinberg <rudi.grinberg@gmail.com>

dune-project

@@ -15,7 +15,7 @@
    base-unix
    base-threads)
   (conflicts
-   (jbuilder (!= "transition"))
+   (jbuilder (<> "transition"))
    (odoc (< 1.3.0)))
   (synopsis "Fast, portable and opinionated build system")
   (description "

src/dune_project.ml

@@ -199,7 +199,7 @@ module Opam = struct
         ; ">", Gt
         ; "<", Lt
         ; "<>", Neq
-        ; "!=", Neq ]
+        ]
 
       let to_dyn =
         let open Dyn.Encoder in
@@ -249,11 +249,15 @@ module Opam = struct
 
       let decode =
         let open Stanza.Decoder in
+        let ops =
+          List.map Op.map ~f:(fun (name, op) ->
+            name, (let+ x = Var.decode in Uop (op, x)))
+        in
+        let ops =
+          ("!=", let+ loc = loc in of_sexp_error loc "Use <> instead of !=")
+          :: ops
+        in
         fix begin fun t ->
-          let ops =
-            List.map Op.map ~f:(fun (name, op) ->
-              name, (let+ x = Var.decode in Uop (op, x)))
-          in
           let logops =
             [ "and", (let+ x = repeat t in And x)
             ; "or", (let+ x = repeat t in Or x)