Support for encoding directives, arg groups, length-prefixed e-expressions

Cargo.toml

@@ -21,7 +21,7 @@ edition = "2021"
 # We need at least 1.65 for GATs[1] and 1.67 for `ilog`[2]
 # [1] https://blog.rust-lang.org/2022/11/03/Rust-1.65.0.html
 # [2] https://blog.rust-lang.org/2023/01/26/Rust-1.67.0.html#stabilized-apis
-rust-version = "1.67"
+rust-version = "1.77"
 
 [features]
 default = []
@@ -63,6 +63,7 @@ smallvec = { version = "1.9.0", features = ["const_generics"] }
 bumpalo = { version = "3.15.3", features = ["collections", "std"] }
 digest = { version = "0.9", optional = true }
 ice_code = "0.1.4"
+rustc-hash = "2.0.0"
 sha2 = { version = "0.9", optional = true }
 serde = { version = "1.0", features = ["derive"], optional = true }
 serde_with = { version = "3.7.0", optional = true }

src/element/sequence.rs

@@ -6,17 +6,34 @@ use crate::lazy::encoding::Encoding;
 use crate::write_config::WriteConfig;
 use crate::IonResult;
 use std::cmp::Ordering;
+use std::fmt::{Debug, Formatter};
 use std::io;
 
 /// An iterable, addressable series of Ion [`Element`]s.
 ///
 /// A `Sequence` is not itself an Ion value type, but can represent a series of Ion values appearing
 /// in a [`List`](crate::List), a [`SExp`](crate::SExp), or at the top level.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Clone, PartialEq, Eq)]
 pub struct Sequence {
     elements: Vec<Element>,
 }
 
+impl Debug for Sequence {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Sequence<")?;
+        let mut is_first = true;
+        for element in self {
+            if is_first {
+                write!(f, "{element}")?;
+            } else {
+                write!(f, ", {element}")?;
+                is_first = false;
+            }
+        }
+        write!(f, ">")
+    }
+}
+
 impl Sequence {
     pub fn new<E: Into<Element>, I: IntoIterator<Item = E>>(elements: I) -> Sequence {
         let elements = elements.into_iter().map(|e| e.into()).collect();