let begin_tokens_of_token = function
END -> [ BEGIN ; OBJECT ; SIG ; STRUCT ]
| IN -> [ LET ]
| DONE -> [ DO ]
| DO -> [ WHILE ; FOR ]
| RPAREN -> [LPAREN]
| RBRACE -> [LBRACE]
| RBRACKET -> [LBRACKET; LBRACKETLESS; LBRACKETGREATER]
| BARRBRACKET -> [LBRACKETBAR]
| GREATERRBRACE -> [LBRACELESS]
| GREATERRBRACKET -> [LBRACKETLESS]
| WITH -> [MATCH;TRY;LBRACE]
| THEN -> [IF]
| ELSE -> [THEN]
| OBJECT -> [CLASS]
| STRUCT | SIG -> [MODULE]
| _ -> assert false