Implement IntoIterator for IMap and IArray via self-reference (#69)

Author: kirillsemyonkin

Cargo.toml

@@ -27,6 +27,7 @@ derive = ["implicit-clone-derive"]
 implicit-clone-derive = { version = "0.1", optional = true, path = "./implicit-clone-derive" }
 indexmap = { version = "2", optional = true }
 serde = { version = "1", optional = true }
+ouroboros = "0.18"
 
 [dev-dependencies]
 static_assertions = "1"

src/array.rs

@@ -1,5 +1,7 @@
 use std::fmt;
 
+use ouroboros::self_referencing;
+
 use super::Rc;
 use crate::ImplicitClone;
 
@@ -110,47 +112,44 @@ impl<T: ImplicitClone + 'static, const N: usize> From<[T; N]> for IArray<T> {
     }
 }
 
-/// An iterator over the cloned elements of an `IArray`.
-#[derive(Debug)]
-pub struct IArrayIntoIter<T: ImplicitClone + 'static> {
+#[self_referencing]
+struct IArrayIntoIterInternal<T: ImplicitClone + 'static> {
     array: IArray<T>,
-    left: usize,
-    right: usize,
+    #[covariant]
+    #[borrows(array)]
+    iter: std::slice::Iter<'this, T>,
 }
 
+/// An iterator over the cloned elements of an `IArray`.
+#[allow(missing_debug_implementations)]
+pub struct IArrayIntoIter<T: ImplicitClone + 'static>(IArrayIntoIterInternal<T>);
+
 impl<T: ImplicitClone + 'static> IntoIterator for IArray<T> {
     type Item = T;
     type IntoIter = IArrayIntoIter<T>;
 
     fn into_iter(self) -> <Self as IntoIterator>::IntoIter {
-        IArrayIntoIter {
-            left: 0,
-            right: self.len(),
-            array: self,
-        }
+        IArrayIntoIter(
+            IArrayIntoIterInternalBuilder {
+                array: self,
+                iter_builder: |a| a.iter(),
+            }
+            .build(),
+        )
     }
 }
 
 impl<T: ImplicitClone + 'static> Iterator for IArrayIntoIter<T> {
     type Item = T;
 
     fn next(&mut self) -> Option<Self::Item> {
-        if self.left >= self.right {
-            return None;
-        }
-        let item = &self.array[self.left];
-        self.left += 1;
-        Some(item.clone())
+        self.0.with_iter_mut(|iter| iter.next().cloned())
     }
 }
 
 impl<T: ImplicitClone + 'static> DoubleEndedIterator for IArrayIntoIter<T> {
     fn next_back(&mut self) -> Option<Self::Item> {
-        if self.left >= self.right {
-            return None;
-        }
-        self.right -= 1;
-        Some(self.array[self.right].clone())
+        self.0.with_iter_mut(|iter| iter.next_back().cloned())
     }
 }
 
@@ -333,7 +332,7 @@ impl<T: ImplicitClone + 'static> IArray<T> {
     }
 }
 
-impl<'a, T, U, const N: usize> PartialEq<&'a [U; N]> for IArray<T>
+impl<T, U, const N: usize> PartialEq<&[U; N]> for IArray<T>
 where
     T: PartialEq<U> + ImplicitClone,
 {
@@ -369,7 +368,7 @@ where
     }
 }
 
-impl<'a, T, U> PartialEq<&'a [U]> for IArray<T>
+impl<T, U> PartialEq<&[U]> for IArray<T>
 where
     T: PartialEq<U> + ImplicitClone,
 {
@@ -490,7 +489,7 @@ mod test_array {
     }
 
     #[test]
-    fn into_iter() {
+    fn iterators() {
         let array = IArray::Static(&[1, 2, 3]);
         assert_eq!(array.iter().next().unwrap(), &1);
         assert_eq!(array.into_iter().next().unwrap(), 1);

src/map.rs

@@ -2,6 +2,7 @@ use indexmap::map::Iter as MapIter;
 use indexmap::map::Keys as MapKeys;
 use indexmap::map::Values as MapValues;
 use indexmap::IndexMap as Map;
+use ouroboros::self_referencing;
 use std::borrow::Borrow;
 use std::fmt;
 use std::hash::Hash;
@@ -308,8 +309,8 @@ impl<'a, K: Eq + Hash + ImplicitClone + 'static, V: PartialEq + ImplicitClone +
     }
 }
 
-impl<'a, K: Eq + Hash + ImplicitClone + 'static, V: PartialEq + ImplicitClone + 'static>
-    DoubleEndedIterator for IMapIter<'a, K, V>
+impl<K: Eq + Hash + ImplicitClone + 'static, V: PartialEq + ImplicitClone + 'static>
+    DoubleEndedIterator for IMapIter<'_, K, V>
 {
     fn next_back(&mut self) -> Option<Self::Item> {
         match self {
@@ -319,6 +320,51 @@ impl<'a, K: Eq + Hash + ImplicitClone + 'static, V: PartialEq + ImplicitClone +
     }
 }
 
+#[self_referencing]
+struct IMapIntoIterInternal<
+    K: Eq + Hash + ImplicitClone + 'static,
+    V: PartialEq + ImplicitClone + 'static,
+> {
+    map: IMap<K, V>,
+    #[covariant]
+    #[borrows(map)]
+    iter: IMapIter<'this, K, V>,
+}
+
+#[allow(missing_docs, missing_debug_implementations)]
+pub struct IMapIntoIter<
+    K: Eq + Hash + ImplicitClone + 'static,
+    V: PartialEq + ImplicitClone + 'static,
+>(IMapIntoIterInternal<K, V>);
+
+impl<K: Eq + Hash + ImplicitClone + 'static, V: PartialEq + ImplicitClone + 'static> IntoIterator
+    for IMap<K, V>
+{
+    type Item = (K, V);
+    type IntoIter = IMapIntoIter<K, V>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        IMapIntoIter(
+            IMapIntoIterInternalBuilder {
+                map: self,
+                iter_builder: |a| a.iter(),
+            }
+            .build(),
+        )
+    }
+}
+
+impl<K: Eq + Hash + ImplicitClone + 'static, V: PartialEq + ImplicitClone + 'static> Iterator
+    for IMapIntoIter<K, V>
+{
+    type Item = (K, V);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.0
+            .with_iter_mut(|iter| iter.next().map(|(k, v)| (k.clone(), v.clone())))
+    }
+}
+
 #[allow(missing_docs, missing_debug_implementations)]
 pub enum IMapKeys<'a, K, V> {
     Slice(std::slice::Iter<'a, (K, V)>),
@@ -338,8 +384,8 @@ impl<'a, K: Eq + Hash + ImplicitClone + 'static, V: PartialEq + ImplicitClone +
     }
 }
 
-impl<'a, K: Eq + Hash + ImplicitClone + 'static, V: PartialEq + ImplicitClone + 'static>
-    DoubleEndedIterator for IMapKeys<'a, K, V>
+impl<K: Eq + Hash + ImplicitClone + 'static, V: PartialEq + ImplicitClone + 'static>
+    DoubleEndedIterator for IMapKeys<'_, K, V>
 {
     fn next_back(&mut self) -> Option<Self::Item> {
         match self {
@@ -368,8 +414,8 @@ impl<'a, K: Eq + Hash + ImplicitClone + 'static, V: PartialEq + ImplicitClone +
     }
 }
 
-impl<'a, K: Eq + Hash + ImplicitClone + 'static, V: PartialEq + ImplicitClone + 'static>
-    DoubleEndedIterator for IMapValues<'a, K, V>
+impl<K: Eq + Hash + ImplicitClone + 'static, V: PartialEq + ImplicitClone + 'static>
+    DoubleEndedIterator for IMapValues<'_, K, V>
 {
     fn next_back(&mut self) -> Option<Self::Item> {
         match self {
@@ -472,4 +518,13 @@ mod test_map {
         let x: IMap<u32, u32> = IMap::Static(&[]);
         let _out = IMap::from(&x);
     }
+
+    #[test]
+    fn iterators() {
+        let map = IMap::Static(&[(1, 10), (2, 20), (3, 30)]);
+        assert_eq!(map.iter().next().unwrap(), (&1, &10));
+        assert_eq!(map.keys().next().unwrap(), &1);
+        assert_eq!(map.values().next().unwrap(), &10);
+        assert_eq!(map.into_iter().next().unwrap(), (1, 10));
+    }
 }