Fix apply bug with keyword

parser.ml

@@ -80,6 +80,10 @@ let token_to_op tok =
 let token_is_operator tok =
   Hashtbl.mem operators tok
 
+let is_keyword = function
+  | "if" | "then" | "else" | "let" -> true
+  | _ -> false
+
 (* common parsers *)
 
 let any seq =
@@ -175,13 +179,12 @@ and let_value seq =
 *)
 and expr pre seq =
   seq |> oneof [
-    (either unary value) @> binop pre;
     ifexpr;
+    oneof [apply; unary; value] @> binop pre;
     level;
     assoc;
     lambda;
     extern_value;
-    apply;
   ]
 
 (* level := "level" {"get" | "set"} [op] *)
@@ -260,6 +263,7 @@ and value seq =
   match seq () with
   | Seq.Nil -> raise End_of_tokens
   | Seq.Cons (x, seq) -> begin match x with
+      | Ident id when is_keyword id -> failwith "value"
       | Ident "true" -> Nbool true, seq
       | Ident "false" -> Nbool false, seq
       | Ident id -> Var id, seq
@@ -293,8 +297,8 @@ and binop pre left seq =
         else
           left, Seq.cons x seq
 
-      | RParen | Ident "then" | Ident "else" ->
-        left, Seq.cons x seq
+      | RParen -> left, Seq.cons x seq
+      | Ident id when is_keyword id -> left, Seq.cons x seq
       | _ -> unexpected_token x
     end