From 178267c701c233542078c09fe6b19802f9642dbd Mon Sep 17 00:00:00 2001
From: HampusM <hampus@hampusmat.com>
Date: Mon, 30 Jan 2023 21:29:21 +0100
Subject: feat: improve macro error messages

---
 macros/src/util/iterator_ext.rs | 42 +++++++++++++++++++++++++++++------------
 1 file changed, 30 insertions(+), 12 deletions(-)

(limited to 'macros/src/util/iterator_ext.rs')

diff --git a/macros/src/util/iterator_ext.rs b/macros/src/util/iterator_ext.rs
index 5001068..17482ae 100644
--- a/macros/src/util/iterator_ext.rs
+++ b/macros/src/util/iterator_ext.rs
@@ -1,26 +1,39 @@
-use std::collections::HashMap;
+use std::collections::HashSet;
 use std::hash::Hash;
 
+/// [`Iterator`] extension trait.
 pub trait IteratorExt<Item>
+where
+    Item: Eq + Hash,
 {
-    fn find_duplicate(&mut self) -> Option<Item>;
+    /// Finds the first occurance of a duplicate item.
+    ///
+    /// This function is short-circuiting. So it will immedietly return `Some` when
+    /// it comes across a item it has already seen.
+    ///
+    /// The returned tuple contains the first item occurance & the second item occurance.
+    /// In that specific order.
+    ///
+    /// Both items are returned in the case of the hash not being representative of the
+    /// whole item.
+    fn find_duplicate(self) -> Option<(Item, Item)>;
 }
 
 impl<Iter> IteratorExt<Iter::Item> for Iter
 where
     Iter: Iterator,
-    Iter::Item: Eq + Hash + Clone,
+    Iter::Item: Eq + Hash,
 {
-    fn find_duplicate(&mut self) -> Option<Iter::Item>
+    fn find_duplicate(self) -> Option<(Iter::Item, Iter::Item)>
     {
-        let mut iterated_item_map = HashMap::<Iter::Item, ()>::new();
+        let mut iterated_item_map = HashSet::<Iter::Item>::new();
 
         for item in self {
-            if iterated_item_map.contains_key(&item) {
-                return Some(item);
+            if let Some(equal_item) = iterated_item_map.take(&item) {
+                return Some((item, equal_item));
             }
 
-            iterated_item_map.insert(item, ());
+            iterated_item_map.insert(item);
         }
 
         None
@@ -33,7 +46,7 @@ mod tests
     use super::*;
 
     #[test]
-    fn can_find_duplicate()
+    fn can_find_dupe()
     {
         #[derive(Debug, PartialEq, Eq, Clone, Hash)]
         struct Fruit
@@ -58,9 +71,14 @@ mod tests
             ]
             .iter()
             .find_duplicate(),
-            Some(&Fruit {
-                name: "Apple".to_string()
-            })
+            Some((
+                &Fruit {
+                    name: "Apple".to_string()
+                },
+                &Fruit {
+                    name: "Apple".to_string()
+                }
+            ))
         );
 
         assert_eq!(
-- 
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