From 34dd95f9098c41497243c60527606e8764e71716 Mon Sep 17 00:00:00 2001
From: "Tobin C. Harding" <me@tobin.cc>
Date: Fri, 12 Jul 2024 13:52:01 +1000
Subject: [PATCH] Debug Midstate forwards

Done in preparation for adding a `length` field to `Midstate` and also
in preparation for removing the `Display` implementation (will be
justified in the patch that does it).

Currently in the `Debug` impl of `Midstate` we are calling through to
`Display` using the alternate form of printing, we can use `as_hex` to
achieve almost the same thing. Note that in `LowerHex` we use the
`fmt_hex_exact` macro that allows us to reverse the iterator however
when we later attempt to use `f.debug_struct` we cannot use the macro.

Elect to change the current behaviour to `Debug` forwards, shown by the
change to the regression test.
---
 hashes/src/sha256.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/hashes/src/sha256.rs b/hashes/src/sha256.rs
index bbc2d27a9..2057fa057 100644
--- a/hashes/src/sha256.rs
+++ b/hashes/src/sha256.rs
@@ -10,6 +10,8 @@ use core::ops::Index;
 use core::slice::SliceIndex;
 use core::{cmp, convert, fmt};
 
+use hex::DisplayHex;
+
 #[cfg(doc)]
 use crate::sha256t;
 use crate::{sha256d, FromSliceError, HashEngine as _};
@@ -195,7 +197,7 @@ impl fmt::Display for Midstate {
 }
 
 impl fmt::Debug for Midstate {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "{:#}", self) }
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "0x{}", self.0.as_hex()) }
 }
 
 impl convert::AsRef<[u8]> for Midstate {
@@ -1019,7 +1021,7 @@ mod tests {
 
     #[test]
     fn regression_midstate_debug_format() {
-        let want = "0xc9f0c6ddea3eb37d606e63476c93f3d389500fc3f2cab338396c117ce6e4e09c";
+        let want = "0x9ce0e4e67c116c3938b3caf2c30f5089d3f3936c47636e607db33eeaddc6f0c9";
         let got = format!("{:?}", TAP_LEAF_MIDSTATE);
         assert_eq!(got, want);
     }