Drop use of RefCell in DebugIter

The `RefCell` was necessary in a previous iteration of the code in which
the iterator was not `Clone` so we needed interior mutability in order
to consume the iterator. Now that it is `Clone`, we can drop it, as
we're no longer mutating the original iterator.

Author: wpaulino

lightning/src/util/logger.rs

@@ -173,18 +173,15 @@ impl<'a> core::fmt::Display for DebugBytes<'a> {
 ///
 /// This is not exported to bindings users as fmt can't be used in C
 #[doc(hidden)]
-pub struct DebugIter<T: fmt::Display, I: core::iter::Iterator<Item = T> + Clone>(pub core::cell::RefCell<I>);
+pub struct DebugIter<T: fmt::Display, I: core::iter::Iterator<Item = T> + Clone>(pub I);
 impl<T: fmt::Display, I: core::iter::Iterator<Item = T> + Clone> fmt::Display for DebugIter<T, I> {
 	fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
-		use core::ops::DerefMut;
 		write!(f, "[")?;
-		let iter_ref = self.0.clone();
-		let mut iter = iter_ref.borrow_mut();
-		for item in iter.deref_mut() {
+		let mut iter = self.0.clone();
+		if let Some(item) = iter.next() {
 			write!(f, "{}", item)?;
-			break;
 		}
-		for item in iter.deref_mut() {
+		while let Some(item) = iter.next() {
 			write!(f, ", {}", item)?;
 		}
 		write!(f, "]")?;

lightning/src/util/macro_logger.rs

@@ -19,7 +19,7 @@ use crate::util::logger::DebugBytes;
 
 macro_rules! log_iter {
 	($obj: expr) => {
-		$crate::util::logger::DebugIter(core::cell::RefCell::new($obj))
+		$crate::util::logger::DebugIter($obj)
 	}
 }