Allow an implicit paren for (: <id> : T ... -> T)
Allow an implicit paren for (: <id> : T ... -> T)

svn: r12038

mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket