todo: arbitrary ir

src/util/scoped_map.rs

@@ -1,6 +1,7 @@
 use std::{borrow::Borrow, collections::HashMap, hash::Hash};
 
 /// A version of [`std::collections::HashMap`] with a built-in notion of scope.
+#[derive(Clone)]
 pub struct ScopedMap<K: Eq + Hash + PartialEq, V> {
     scopes: Vec<HashMap<K, V>>,
 }
@@ -84,4 +85,24 @@ impl<K: Eq + Hash + PartialEq, V> ScopedMap<K, V> {
     pub fn release_scope(&mut self) -> Option<HashMap<K, V>> {
         self.scopes.pop()
     }
+
+    /// Create a new scoped set by mapping over the values of this one.
+    pub fn map_values<F, W>(self, f: F) -> ScopedMap<K, W>
+    where
+        F: Fn(V) -> W,
+    {
+        let mut scopes = Vec::with_capacity(self.scopes.len());
+
+        for scope in self.scopes {
+            let mut map = HashMap::with_capacity(scope.len());
+
+            for (k, v) in scope {
+                map.insert(k, f(v));
+            }
+
+            scopes.push(map);
+        }
+
+        ScopedMap { scopes }
+    }
 }