. It certainly does not convert Rule 16 into a general limitation on the trial court's broad discretion as t evidentiary questions at tri- al. Cf. Giles I. Maryland, 386 U.S. 66, 101, 87 S.Ct. 793, 810, 17 L.Ed.2d 737 (1967) (Fortes, J., concurring in judgment). ?to We conclude, therefore, that Rule 16 impose