coercion = [
SYMBOL ":" -> false,0
| SYMBOL ":"; SYMBOL ">" -> true,0
| SYMBOL ":"; arity = int ; SYMBOL ">" -> true,arity
];
ty = term ->
coercion = [
SYMBOL ":" -> false,0
| SYMBOL ":"; SYMBOL ">" -> true,0
| SYMBOL ":"; arity = int ; SYMBOL ">" -> true,arity
];
ty = term ->