Correctly feature gate impl_to_hex_from_lower_hex

Currently we feature gate code within the `impl_to_hex_from_lower_hex`
 macro on "alloc" but `bitcoin` does not have the "alloc" feature so
 this code is never built in. This can be seen by the lack of a
 `to_hex` function on `LeafVersion`.

Remove the feature gate from the macro and put it on the individual
call sites as needed.

internals/src/macros.rs

@@ -219,7 +219,6 @@ macro_rules! impl_to_hex_from_lower_hex {
     ($t:ident, $hex_len_fn:expr) => {
         impl $t {
             /// Gets the hex representation of this type
-            #[cfg(feature = "alloc")]
             pub fn to_hex(&self) -> alloc::string::String {
                 use core::fmt::Write;
 

primitives/src/pow.rs

@@ -4,8 +4,6 @@
 
 use core::fmt;
 
-use internals::impl_to_hex_from_lower_hex;
-
 /// Encoding of 256-bit target as 32-bit float.
 ///
 /// This is used to encode a target into the block header. Satoshi made this part of consensus code
@@ -36,7 +34,8 @@ impl fmt::LowerHex for CompactTarget {
     #[inline]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { fmt::LowerHex::fmt(&self.0, f) }
 }
-impl_to_hex_from_lower_hex!(CompactTarget, |compact_target: &CompactTarget| {
+#[cfg(feature = "alloc")]
+internals::impl_to_hex_from_lower_hex!(CompactTarget, |compact_target: &CompactTarget| {
     8 - compact_target.0.leading_zeros() as usize / 4
 });
 

primitives/src/script/mod.rs

@@ -12,7 +12,6 @@ use core::fmt;
 use core::ops::{Deref, DerefMut};
 
 use hex::DisplayHex;
-use internals::impl_to_hex_from_lower_hex;
 use internals::script::{self, PushDataLenLen};
 
 use crate::opcodes::all::*;
@@ -231,13 +230,15 @@ impl fmt::LowerHex for Script {
         fmt::LowerHex::fmt(&self.as_bytes().as_hex(), f)
     }
 }
-impl_to_hex_from_lower_hex!(Script, |script: &Script| script.len() * 2);
+#[cfg(feature = "alloc")]
+internals::impl_to_hex_from_lower_hex!(Script, |script: &Script| script.len() * 2);
 
 impl fmt::LowerHex for ScriptBuf {
     #[inline]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { fmt::LowerHex::fmt(self.as_script(), f) }
 }
-impl_to_hex_from_lower_hex!(ScriptBuf, |script_buf: &ScriptBuf| script_buf.len() * 2);
+#[cfg(feature = "alloc")]
+internals::impl_to_hex_from_lower_hex!(ScriptBuf, |script_buf: &ScriptBuf| script_buf.len() * 2);
 
 impl fmt::UpperHex for Script {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {

primitives/src/sequence.rs

@@ -19,7 +19,6 @@ use core::fmt;
 
 #[cfg(feature = "arbitrary")]
 use arbitrary::{Arbitrary, Unstructured};
-use internals::impl_to_hex_from_lower_hex;
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 #[cfg(feature = "alloc")]
@@ -231,7 +230,8 @@ impl fmt::Display for Sequence {
 impl fmt::LowerHex for Sequence {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { fmt::LowerHex::fmt(&self.0, f) }
 }
-impl_to_hex_from_lower_hex!(Sequence, |sequence: &Sequence| {
+#[cfg(feature = "alloc")]
+internals::impl_to_hex_from_lower_hex!(Sequence, |sequence: &Sequence| {
     8 - sequence.0.leading_zeros() as usize / 4
 });