1 files changed, 102 insertions, 0 deletions
diff --git a/tvix/eval/src/value/list.rs b/tvix/eval/src/value/list.rs
new file mode 100644
index 000000000000..2b8b3de28d19
--- /dev/null
+++ b/tvix/eval/src/value/list.rs
@@ -0,0 +1,102 @@
+//! This module implements Nix lists.
+use std::ops::Index;
+use std::rc::Rc;
+
+use imbl::{vector, Vector};
+
+use serde::Deserialize;
+
+use super::thunk::ThunkSet;
+use super::TotalDisplay;
+use super::Value;
+
+#[repr(transparent)]
+#[derive(Clone, Debug, Deserialize)]
+pub struct NixList(Rc<Vector<Value>>);
+
+impl TotalDisplay for NixList {
+    fn total_fmt(&self, f: &mut std::fmt::Formatter<'_>, set: &mut ThunkSet) -> std::fmt::Result {
+        f.write_str("[ ")?;
+
+        for v in self {
+            v.total_fmt(f, set)?;
+            f.write_str(" ")?;
+        }
+
+        f.write_str("]")
+    }
+}
+
+impl From<Vector<Value>> for NixList {
+    fn from(vs: Vector<Value>) -> Self {
+        Self(Rc::new(vs))
+    }
+}
+
+impl NixList {
+    pub fn len(&self) -> usize {
+        self.0.len()
+    }
+
+    pub fn get(&self, i: usize) -> Option<&Value> {
+        self.0.get(i)
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.0.is_empty()
+    }
+
+    pub fn construct(count: usize, stack_slice: Vec<Value>) -> Self {
+        debug_assert!(
+            count == stack_slice.len(),
+            "NixList::construct called with count == {}, but slice.len() == {}",
+            count,
+            stack_slice.len(),
+        );
+
+        NixList(Rc::new(Vector::from_iter(stack_slice)))
+    }
+
+    pub fn iter(&self) -> vector::Iter<Value> {
+        self.0.iter()
+    }
+
+    pub fn ptr_eq(&self, other: &Self) -> bool {
+        Rc::ptr_eq(&self.0, &other.0)
+    }
+
+    pub fn into_inner(self) -> Vector<Value> {
+        Rc::try_unwrap(self.0).unwrap_or_else(|rc| (*rc).clone())
+    }
+
+    #[deprecated(note = "callers should avoid constructing from Vec")]
+    pub fn from_vec(vs: Vec<Value>) -> Self {
+        Self(Rc::new(Vector::from_iter(vs)))
+    }
+}
+
+impl IntoIterator for NixList {
+    type Item = Value;
+    type IntoIter = imbl::vector::ConsumingIter<Value>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.into_inner().into_iter()
+    }
+}
+
+impl<'a> IntoIterator for &'a NixList {
+    type Item = &'a Value;
+    type IntoIter = imbl::vector::Iter<'a, Value>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.iter()
+    }
+}
+
+impl Index<usize> for NixList {
+    type Output = Value;
+
+    fn index(&self, index: usize) -> &Self::Output {
+        &self.0[index]
+    }
+}