check: bounds-check roslice peeks, not just slice
diff --git a/lang/check/bounds.go b/lang/check/bounds.go
index 51b64e7..887b25d 100644
--- a/lang/check/bounds.go
+++ b/lang/check/bounds.go
@@ -1259,7 +1259,7 @@
 			}
 		}
 
-	} else if recvTyp.Eq(typeExprSliceU8) {
+	} else if recvTyp.Eq(typeExprSliceU8) || recvTyp.Eq(typeExprRosliceU8) {
 		if method >= t.IDPeekU8 {
 			if m := method - t.IDPeekU8; m < t.ID(len(ioMethodAdvances)) {
 				au := ioMethodAdvances[m]