Do not use redundant closures

Clippy emits:

 warning: redundant closure

As suggested, remove the redundant closures. Doing so causes a
variable to no longer require mut, fix that also.

Author: tcharding

src/descriptor/key.rs

@@ -456,7 +456,7 @@ impl FromStr for DescriptorPublicKey {
                     derivation_path: derivation_paths
                         .into_iter()
                         .next()
-                        .unwrap_or_else(|| bip32::DerivationPath::default()),
+                        .unwrap_or_else(bip32::DerivationPath::default),
                     wildcard,
                 }))
             }
@@ -719,7 +719,7 @@ impl FromStr for DescriptorSecretKey {
                     derivation_path: derivation_paths
                         .into_iter()
                         .next()
-                        .unwrap_or_else(|| bip32::DerivationPath::default()),
+                        .unwrap_or_else(bip32::DerivationPath::default),
                     wildcard,
                 }))
             }

src/descriptor/sortedmulti.rs

@@ -112,11 +112,11 @@ impl<Pk: MiniscriptKey, Ctx: ScriptContext> SortedMultiVec<Pk, Ctx> {
 }
 
 impl<Pk: MiniscriptKey, Ctx: ScriptContext> ForEachKey<Pk> for SortedMultiVec<Pk, Ctx> {
-    fn for_each_key<'a, F: FnMut(&'a Pk) -> bool>(&'a self, mut pred: F) -> bool
+    fn for_each_key<'a, F: FnMut(&'a Pk) -> bool>(&'a self, pred: F) -> bool
     where
         Pk: 'a,
     {
-        self.pks.iter().all(|key| pred(key))
+        self.pks.iter().all(pred)
     }
 }
 

src/miniscript/astelem.rs

@@ -113,9 +113,7 @@ impl<Pk: MiniscriptKey, Ctx: ScriptContext> Terminal<Pk, Ctx> {
                     && c.real_for_each_key(pred)
             }
             Terminal::Thresh(_, ref subs) => subs.iter().all(|sub| sub.real_for_each_key(pred)),
-            Terminal::Multi(_, ref keys) | Terminal::MultiA(_, ref keys) => {
-                keys.iter().all(|key| pred(key))
-            }
+            Terminal::Multi(_, ref keys) | Terminal::MultiA(_, ref keys) => keys.iter().all(pred),
         }
     }