feat: rec attrset

evaluator/nixjit_eval/src/value/attrset.rs

@@ -5,6 +5,7 @@ use std::fmt::Debug;
 use std::rc::Rc;
 
 use derive_more::Constructor;
+use hashbrown::hash_map::Entry;
 use hashbrown::{HashMap, HashSet};
 use itertools::Itertools;
 
@@ -13,14 +14,13 @@ use nixjit_value::Symbol;
 use nixjit_value::{self as p, format_symbol};
 
 use super::Value;
-use crate::EvalContext;
 
 /// A wrapper around a `HashMap` representing a Nix attribute set.
 ///
 /// It uses `#[repr(transparent)]` to ensure it has the same memory layout
 /// as `HashMap<String, Value>`.
 #[repr(transparent)]
-#[derive(Constructor, PartialEq)]
+#[derive(Clone, Constructor, PartialEq)]
 pub struct AttrSet {
     data: HashMap<String, Value>,
 }
@@ -40,14 +40,6 @@ impl Debug for AttrSet {
     }
 }
 
-impl Clone for AttrSet {
-    fn clone(&self) -> Self {
-        AttrSet {
-            data: self.data.clone(),
-        }
-    }
-}
-
 impl From<HashMap<String, Value>> for AttrSet {
     fn from(data: HashMap<String, Value>) -> Self {
         Self { data }
@@ -80,11 +72,17 @@ impl AttrSet {
     ///
     /// This method currently uses `todo!()` and will panic if the attribute
     /// already exists, indicating that duplicate attribute handling is not yet implemented.
-    pub fn push_attr(&mut self, sym: String, val: Value) {
-        if self.data.get(&sym).is_some() {
-            todo!()
+    pub fn push_attr(&mut self, sym: String, val: Value) -> Result<()> {
+        match self.data.entry(sym) {
+            Entry::Occupied(occupied) => Err(Error::EvalError(format!(
+                "attribute '{}' already defined",
+                format_symbol(occupied.key())
+            ))),
+            Entry::Vacant(vacant) => {
+                vacant.insert(val);
+                Ok(())
+            }
         }
-        self.data.insert(sym, val);
     }
 
     /// Performs a deep selection of an attribute from a nested set.