2 files changed, 68 insertions, 22 deletions

diff --git a/src/eval/dict.rs b/src/eval/dict.rs
index 7f4426ff..b0d5fb82 100644
--- a/src/eval/dict.rs
+++ b/src/eval/dict.rs
@@ -2,6 +2,7 @@
 
 use std::collections::BTreeMap;
 use std::fmt::{self, Debug, Display, Formatter};
+use std::iter::Extend;
 use std::ops::Index;
 
 use crate::syntax::{Span, Spanned};
@@ -117,9 +118,7 @@ impl<V> Dict<V> {
 
     /// Iterator over all borrowed keys and values.
     pub fn iter(&self) -> impl Iterator<Item = (RefKey, &V)> {
-        self.nums()
-            .map(|(&k, v)| (RefKey::Num(k), v))
-            .chain(self.strs().map(|(k, v)| (RefKey::Str(k), v)))
+        self.into_iter()
     }
 
     /// Iterate over all values in the dictionary.
@@ -137,14 +136,6 @@ impl<V> Dict<V> {
         self.strs.iter()
     }
 
-    /// Move into an owned iterator over owned keys and values.
-    pub fn into_iter(self) -> impl Iterator<Item = (DictKey, V)> {
-        self.nums
-            .into_iter()
-            .map(|(k, v)| (DictKey::Num(k), v))
-            .chain(self.strs.into_iter().map(|(k, v)| (DictKey::Str(k), v)))
-    }
-
     /// Move into an owned iterator over all values in the dictionary.
     pub fn into_values(self) -> impl Iterator<Item = V> {
         self.nums
@@ -164,17 +155,6 @@ impl<V> Dict<V> {
     }
 }
 
-impl<'a, K, V> Index<K> for Dict<V>
-where
-    K: Into<RefKey<'a>>,
-{
-    type Output = V;
-
-    fn index(&self, index: K) -> &Self::Output {
-        self.get(index).expect("key not in dict")
-    }
-}
-
 impl<V> Default for Dict<V> {
     fn default() -> Self {
         Self::new()
@@ -189,6 +169,68 @@ impl<V: PartialEq> PartialEq for Dict<V> {
     }
 }
 
+impl<V> IntoIterator for Dict<V> {
+    type Item = (DictKey, V);
+    type IntoIter = std::iter::Chain<
+        std::iter::Map<
+            std::collections::btree_map::IntoIter<u64, V>,
+            fn((u64, V)) -> (DictKey, V),
+        >,
+        std::iter::Map<
+            std::collections::btree_map::IntoIter<String, V>,
+            fn((String, V)) -> (DictKey, V),
+        >,
+    >;
+
+    fn into_iter(self) -> Self::IntoIter {
+        let nums = self.nums.into_iter().map((|(k, v)| (DictKey::Num(k), v)) as _);
+        let strs = self.strs.into_iter().map((|(k, v)| (DictKey::Str(k), v)) as _);
+        nums.chain(strs)
+    }
+}
+
+impl<'a, V> IntoIterator for &'a Dict<V> {
+    type Item = (RefKey<'a>, &'a V);
+    type IntoIter = std::iter::Chain<
+        std::iter::Map<
+            std::collections::btree_map::Iter<'a, u64, V>,
+            fn((&'a u64, &'a V)) -> (RefKey<'a>, &'a V),
+        >,
+        std::iter::Map<
+            std::collections::btree_map::Iter<'a, String, V>,
+            fn((&'a String, &'a V)) -> (RefKey<'a>, &'a V),
+        >,
+    >;
+
+    fn into_iter(self) -> Self::IntoIter {
+        let strs = self.strs().map((|(k, v): (&'a String, _)| (RefKey::Str(k), v)) as _);
+        let nums = self.nums().map((|(k, v): (&u64, _)| (RefKey::Num(*k), v)) as _);
+        nums.chain(strs)
+    }
+}
+
+impl<V> Extend<(DictKey, V)> for Dict<V> {
+    fn extend<T>(&mut self, iter: T)
+    where
+        T: IntoIterator<Item = (DictKey, V)>,
+    {
+        for (key, value) in iter.into_iter() {
+            self.insert(key, value);
+        }
+    }
+}
+
+impl<'a, K, V> Index<K> for Dict<V>
+where
+    K: Into<RefKey<'a>>,
+{
+    type Output = V;
+
+    fn index(&self, index: K) -> &Self::Output {
+        self.get(index).expect("key not in dict")
+    }
+}
+
 impl<V: Debug> Debug for Dict<V> {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         if self.is_empty() {
diff --git a/src/eval/value.rs b/src/eval/value.rs
index 51bc55ab..85ac2367 100644
--- a/src/eval/value.rs
+++ b/src/eval/value.rs
@@ -17,6 +17,8 @@ use crate::{DynFuture, Feedback, Pass};
 /// A computational value.
 #[derive(Clone, PartialEq)]
 pub enum Value {
+    /// The result of invalid operations.
+    Error,
     /// An identifier: `ident`.
     Ident(Ident),
     /// A boolean: `true, false`.
@@ -54,6 +56,7 @@ impl Value {
     /// The natural-language name of this value for use in error messages.
     pub fn name(&self) -> &'static str {
         match self {
+            Self::Error => "error",
             Self::Ident(_) => "identifier",
             Self::Bool(_) => "bool",
             Self::Int(_) => "integer",
@@ -111,6 +114,7 @@ impl Spanned<Value> {
 impl Debug for Value {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         match self {
+            Self::Error => f.pad("<error>"),
             Self::Ident(i) => i.fmt(f),
             Self::Bool(b) => b.fmt(f),
             Self::Int(i) => i.fmt(f),