Merge rust-bitcoin/rust-bitcoin#1121: Use u8::try_from

517059e Use u8::try_from (Tobin C. Harding)

Pull request description:

  Currently we use a cast to get the `u8` depth, as suggested by the TODO in the code we can now use `TryFrom` since we bumped the MSRV.

  Use `u8::try_from.expect("")` since depth (node count) is guarded by `TAPROOT_CONTROL_MAX_NODE_COUNT`.

ACKs for top commit:
  Kixunil:
    ACK 517059e
  apoelstra:
    ACK 517059e

Tree-SHA512: 98e58617247a05025ec13ad3d00a464cb2351c98c6d871be43b252d3982e291b7187e25780e7fe367f5a3a64fa20f3b328876a8901af4da09e675f50727a26cf

Author: apoelstra

src/util/taproot.rs

@@ -610,9 +610,8 @@ impl ScriptLeaf {
     /// Returns the depth of this script leaf in the tap tree.
     #[inline]
     pub fn depth(&self) -> u8 {
-        // The depth is guaranteed to be < 127 by the TaprootBuilder type.
-        // TODO: Following MSRV bump implement via `try_into().expect("")`.
-        self.merkle_branch.0.len() as u8
+        // Depth is guarded by TAPROOT_CONTROL_MAX_NODE_COUNT.
+        u8::try_from(self.merkle_branch.0.len()).expect("depth is guaranteed to fit in a u8")
     }
 
     /// Computes a leaf hash for this [`ScriptLeaf`].