Use conventional spacing for default type parameters

The exact code formatting we use is not as important as uniformity.
Since we do not use tooling to control the formatting we have to be
vigilant ourselves. Recently I (Tobin) changed the way default type
parameters were formatted (arbitrarily but uniformly). Turns out I
picked the wrong way, there is already a convention as shown in the rust
documentation online (e.g. [1]).

Use 'conventional' spacing for default type parameters. Make the change
across the whole repository, found using

    git grep '\<.* = .*\>'

[1] - https://doc.rust-lang.org/book/ch19-03-advanced-traits.html

src/util/amount.rs

@@ -946,7 +946,7 @@ pub trait CheckedSum<R>: private::SumSeal<R> {
     fn checked_sum(self) -> Option<R>;
 }
 
-impl<T> CheckedSum<Amount> for T where T: Iterator<Item = Amount> {
+impl<T> CheckedSum<Amount> for T where T: Iterator<Item=Amount> {
     fn checked_sum(mut self) -> Option<Amount> {
         let first = Some(self.next().unwrap_or_default());
 
@@ -957,7 +957,7 @@ impl<T> CheckedSum<Amount> for T where T: Iterator<Item = Amount> {
     }
 }
 
-impl<T> CheckedSum<SignedAmount> for T where T: Iterator<Item = SignedAmount> {
+impl<T> CheckedSum<SignedAmount> for T where T: Iterator<Item=SignedAmount> {
     fn checked_sum(mut self) -> Option<SignedAmount> {
         let first = Some(self.next().unwrap_or_default());
 
@@ -971,8 +971,8 @@ mod private {
     /// Used to seal the `CheckedSum` trait
     pub trait SumSeal<A> {}
 
-    impl<T> SumSeal<Amount> for T where T: Iterator<Item = Amount> {}
+    impl<T> SumSeal<Amount> for T where T: Iterator<Item=Amount> {}
-    impl<T> SumSeal<SignedAmount> for T where T: Iterator<Item = SignedAmount> {}
+    impl<T> SumSeal<SignedAmount> for T where T: Iterator<Item=SignedAmount> {}
 }
 
 #[cfg(feature = "serde")]

src/util/base58.rs

@@ -178,7 +178,7 @@ pub fn from_check(data: &str) -> Result<Vec<u8>, Error> {
 
 fn format_iter<I, W>(writer: &mut W, data: I) -> Result<(), fmt::Error>
 where
-    I: Iterator<Item = u8> + Clone,
+    I: Iterator<Item=u8> + Clone,
     W: fmt::Write
 {
     let mut ret = SmallVec::new();
@@ -219,7 +219,7 @@ where
 
 fn encode_iter<I>(data: I) -> String
 where
-    I: Iterator<Item = u8> + Clone,
+    I: Iterator<Item=u8> + Clone,
 {
     let mut ret = String::new();
     format_iter(&mut ret, data).expect("writing into string shouldn't fail");

src/util/bip32.rs

@@ -284,7 +284,7 @@ impl<'a> From<&'a [ChildNumber]> for DerivationPath {
 }
 
 impl ::core::iter::FromIterator<ChildNumber> for DerivationPath {
-    fn from_iter<T>(iter: T) -> Self where T: IntoIterator<Item = ChildNumber> {
+    fn from_iter<T>(iter: T) -> Self where T: IntoIterator<Item=ChildNumber> {
         DerivationPath(Vec::from_iter(iter))
     }
 }

src/util/hash.rs

@@ -57,7 +57,7 @@ pub fn bitcoin_merkle_root<T, I>(mut hashes: I) -> Option<T>
 where
     T: Hash + Encodable,
     <T as Hash>::Engine: io::Write,
-    I: Iterator<Item = T>,
+    I: Iterator<Item=T>,
 {
     let first = hashes.next()?;
     let second = match hashes.next() {

src/util/psbt/raw.rs

@@ -56,7 +56,7 @@ pub type ProprietaryType = u8;
 /// structure according to BIP 174.
 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct ProprietaryKey<Subtype = ProprietaryType> where Subtype: Copy + From<u8> + Into<u8> {
+pub struct ProprietaryKey<Subtype=ProprietaryType> where Subtype: Copy + From<u8> + Into<u8> {
     /// Proprietary type prefix used for grouping together keys under some
     /// application and avoid namespace collision
     #[cfg_attr(feature = "serde", serde(with = "::serde_utils::hex_bytes"))]

src/util/sighash.rs

@@ -36,7 +36,7 @@ use super::taproot::LeafVersion;
 
 /// Efficiently calculates signature hash message for legacy, segwit and taproot inputs.
 #[derive(Debug)]
-pub struct SigHashCache<T: Deref<Target = Transaction>> {
+pub struct SigHashCache<T: Deref<Target=Transaction>> {
     /// Access to transaction required for various introspection, moreover type
     /// `T: Deref<Target=Transaction>` allows to accept borrow and mutable borrow, the
     /// latter in particular is necessary for [`SigHashCache::witness_mut`]
@@ -295,7 +295,7 @@ impl SchnorrSigHashType {
     }
 }
 
-impl<R: Deref<Target = Transaction>> SigHashCache<R> {
+impl<R: Deref<Target=Transaction>> SigHashCache<R> {
     /// Compute the sighash components from an unsigned transaction and auxiliary
     /// in a lazy manner when required.
     /// For the generated sighashes to be valid, no fields in the transaction may change except for
@@ -692,7 +692,7 @@ impl<R: Deref<Target = Transaction>> SigHashCache<R> {
     }
 }
 
-impl<R: DerefMut<Target = Transaction>> SigHashCache<R> {
+impl<R: DerefMut<Target=Transaction>> SigHashCache<R> {
     /// When the SigHashCache is initialized with a mutable reference to a transaction instead of a
     /// regular reference, this method is available to allow modification to the witnesses.
     ///

src/util/taproot.rs

@@ -215,7 +215,7 @@ impl TaprootSpendInfo {
         script_weights: I,
     ) -> Result<Self, TaprootBuilderError>
     where
-        I: IntoIterator<Item = (u32, Script)>,
+        I: IntoIterator<Item=(u32, Script)>,
         C: secp256k1::Verification,
     {
         let mut node_weights = BinaryHeap::<(Reverse<u64>, NodeInfo)>::new();