clippy: a couple tiny fixes

Clippy prefers we do string slicing after conversion to bytes, not
before, which may be more efficient (at least, in elimantes some panic
paths which we know are impossible since our strings are ASCII, but the
compiler probably doesn't).

It also changes some nested lists in docs to use 1/2/3 numbering because
that's what rustdoc recognizes (and clippy complains about weird
indentation with the existing a/b/c sublist).

Author: apoelstra

src/descriptor/checksum.rs

@@ -112,7 +112,7 @@ pub fn verify_checksum(s: &str) -> Result<&str, Error> {
         }
 
         let mut eng = Engine::new();
-        eng.input_unchecked(s[..last_hash_pos].as_bytes());
+        eng.input_unchecked(&s.as_bytes()[..last_hash_pos]);
 
         let expected = eng.checksum_chars();
 

src/descriptor/mod.rs

@@ -549,6 +549,7 @@ impl Descriptor<DefiniteDescriptorKey> {
     /// Returns a plan if the provided assets are sufficient to produce a non-malleable satisfaction
     ///
     /// If the assets aren't sufficient for generating a Plan, the descriptor is returned
+    #[allow(clippy::result_large_err)] // our "error type" is the original descriptor
     pub fn plan<P>(self, provider: &P) -> Result<Plan, Self>
     where
         P: AssetProvider<DefiniteDescriptorKey>,
@@ -577,6 +578,7 @@ impl Descriptor<DefiniteDescriptorKey> {
     /// Returns a plan if the provided assets are sufficient to produce a malleable satisfaction
     ///
     /// If the assets aren't sufficient for generating a Plan, the descriptor is returned
+    #[allow(clippy::result_large_err)] // our "error type" is the original descriptor
     pub fn plan_mall<P>(self, provider: &P) -> Result<Plan, Self>
     where
         P: AssetProvider<DefiniteDescriptorKey>,

src/miniscript/analyzable.rs

@@ -18,8 +18,8 @@ use crate::{Miniscript, MiniscriptKey, ScriptContext, Terminal};
 /// This allows parsing miniscripts if
 /// 1. It is unsafe(does not require a digital signature to spend it)
 /// 2. It contains a unspendable path because of either
-///     a. Resource limitations
-///     b. Timelock Mixing
+///     1. Resource limitations
+///     2. Timelock Mixing
 /// 3. The script is malleable and thereby some of satisfaction weight
 ///    guarantees are not satisfied.
 /// 4. It has repeated public keys
@@ -124,8 +124,8 @@ impl ExtParams {
 /// We currently mark Miniscript as Non-Analyzable if
 /// 1. It is unsafe(does not require a digital signature to spend it)
 /// 2. It contains a unspendable path because of either
-///     a. Resource limitations
-///     b. Timelock Mixing
+///     1. Resource limitations
+///     2. Timelock Mixing
 /// 3. The script is malleable and thereby some of satisfaction weight
 ///    guarantees are not satisfied.
 /// 4. It has repeated publickeys

src/psbt/mod.rs

@@ -480,6 +480,7 @@ pub trait PsbtExt {
     ///  Returns a tuple containing
     /// - Original psbt
     /// - Input Error detailing why the input finalization failed
+    #[allow(clippy::result_large_err)] // our "error type" includes the original PSBT
     fn finalize_inp<C: secp256k1::Verification>(
         self,
         secp: &secp256k1::Secp256k1<C>,
@@ -494,6 +495,7 @@ pub trait PsbtExt {
     ) -> Result<(), Error>;
 
     /// Same as [`PsbtExt::finalize_inp`], but allows for malleable satisfactions
+    #[allow(clippy::result_large_err)] // our "error type" includes the original PSBT
     fn finalize_inp_mall<C: secp256k1::Verification>(
         self,
         secp: &secp256k1::Secp256k1<C>,