Changed the line comments to start with "//". The list constructor is now "#".

LexToken.mll

@@ -246,7 +246,7 @@ let to_lexeme = function
 | RBRACE   _ -> "}"
 | LBRACKET _ -> "["
 | RBRACKET _ -> "]"
-| CONS     _ -> "<:"
+| CONS     _ -> "#"
 | VBAR     _ -> "|"
 | ARROW    _ -> "->"
 | ASS      _ -> ":="
@@ -490,7 +490,7 @@ let mk_sym lexeme region =
   | "}"   -> RBRACE   region
   | "["   -> LBRACKET region
   | "]"   -> RBRACKET region
-  | "<:"  -> CONS     region
+  | "#"   -> CONS     region
   | "|"   -> VBAR     region
   | "->"  -> ARROW    region
   | ":="  -> ASS      region

Lexer.mll

@@ -166,7 +166,7 @@ module Make (Token: TOKEN) : (S with module Token = Token) =
 
     (* When scanning structured constructs, like strings and comments,
        we need to keep the region of the opening symbol (like double
-       quote, "#" or "(*") in order to report any error more
+       quote, "//" or "(*") in order to report any error more
        precisely. Since ocamllex is byte-oriented, we need to store
        the parsed bytes as characters in an accumulator [acc] and
        also its length [len], so, we are done, it is easy to build the
@@ -443,7 +443,7 @@ let esc        = "\\n" | "\\\"" | "\\\\" | "\\b"
                | "\\r" | "\\t" | "\\x" byte
 let symbol     = ';' | ','
                | '(' | ')' | '{' | '}' | '[' | ']'
-               | "<:" | '|' | "->" | ":=" | '=' | ':'
+               | "#" | '|' | "->" | ":=" | '=' | ':'
                | "||" | "&&" | '<' | "<=" | '>' | ">=" | "=/="
                | '+' | '-' | '*' | '.' | '_' | '^'
 
@@ -482,8 +482,8 @@ and scan state = parse
          let state = scan_block thread state lexbuf |> push_block
          in scan state lexbuf }
 
-| '#'  { let opening, _, state = sync state lexbuf in
-         let thread = {opening; len=1; acc=['#']} in
+| "//"  { let opening, _, state = sync state lexbuf in
+         let thread = {opening; len=2; acc=['/';'/']} in
          let state = scan_line thread state lexbuf |> push_line
          in scan state lexbuf }
 

Tests/a.li

@@ -3,7 +3,7 @@ type u is t
 type v is record foo: key; bar: mutez; baz: address end
 type w is K of (U of int) (*v * u*)
 
-parameter p : v   // Line comment
+parameter p : v;   // Line comment
 storage w
 operations u