From 1de142487f27d472daf22c04a4eebd38fd7f8758 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ivan=20=E2=80=9CCLOVIS=E2=80=9D=20Canet?=
 <ivan.canet@gmail.com>
Date: Sat, 7 Feb 2026 22:19:17 +0100
Subject: [PATCH] fix(enumset): Fix the iterator().remove() method

According to the specification, it wasn't always removing the correct element.
---
 enumset/src/commonMain/kotlin/Bit32.kt        |  9 +++--
 .../kotlin/datatypes/EnumSetSuite.kt          |  3 +-
 .../commonTest/kotlin/datatypes/SetSuite.kt   | 33 ++++++++++++++++++-
 3 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/enumset/src/commonMain/kotlin/Bit32.kt b/enumset/src/commonMain/kotlin/Bit32.kt
index 4430d83..52198ff 100644
--- a/enumset/src/commonMain/kotlin/Bit32.kt
+++ b/enumset/src/commonMain/kotlin/Bit32.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2025, OpenSavvy and contributors.
+ * Copyright (c) 2025-2026, OpenSavvy and contributors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -209,6 +209,7 @@ class MutableBitSet32 internal constructor(private var storage: BitSet32) : Muta
 		private val set: MutableBitSet32,
 	) : MutableIterator<Int> {
 		private var index = 0
+		private var lastIndexReturned = -1
 
 		override fun hasNext(): Boolean {
 			while (index < 32) {
@@ -227,11 +228,15 @@ class MutableBitSet32 internal constructor(private var storage: BitSet32) : Muta
 				throw NoSuchElementException()
 			}
 
+			lastIndexReturned = index
 			return index++
 		}
 
 		override fun remove() {
-			set.remove(index)
+			check(lastIndexReturned != -1) { "Cannot remove an item before next() is called at least once" }
+			check(lastIndexReturned != -2) { "Cannot remove an item multiple times. remove() removes the last item viewed by next(), but it has already been removed" }
+			set.remove(lastIndexReturned)
+			lastIndexReturned = -2
 		}
 	}
 
diff --git a/enumset/src/commonTest/kotlin/datatypes/EnumSetSuite.kt b/enumset/src/commonTest/kotlin/datatypes/EnumSetSuite.kt
index 02c3613..ecd6f9f 100644
--- a/enumset/src/commonTest/kotlin/datatypes/EnumSetSuite.kt
+++ b/enumset/src/commonTest/kotlin/datatypes/EnumSetSuite.kt
@@ -488,9 +488,10 @@ fun <E : Enum<E>> SuiteDsl.testMutableEnumSetValidity(
 
 				check(iter.hasNext())
 				check(iter.next() == entries[0])
+				iter.remove()
 
 				check(iter.hasNext())
-				iter.remove()
+				check(iter.next() == entries[1])
 
 				println("After removal: $set")
 
diff --git a/enumset/src/commonTest/kotlin/datatypes/SetSuite.kt b/enumset/src/commonTest/kotlin/datatypes/SetSuite.kt
index e27362a..8316e69 100644
--- a/enumset/src/commonTest/kotlin/datatypes/SetSuite.kt
+++ b/enumset/src/commonTest/kotlin/datatypes/SetSuite.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2025, OpenSavvy and contributors.
+ * Copyright (c) 2025-2026, OpenSavvy and contributors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -405,9 +405,40 @@ fun SuiteDsl.testMutableSetValidity(
 			check(iter.hasNext())
 			iter.remove()
 
+			// 'remove' deletes the last item returned by 'next', NOT the last item as seen by hasNext
+			check(5 !in set)
+			check(7 in set)
+			check(9 in set)
+			check(set.size == 2)
+
+			check(iter.next() == 7)
+
 			check(iter.hasNext())
 			check(iter.next() == 9)
 		}
+
+		test("Cannot remove an item before reading the first element") {
+			val set = create(arrayOf(5, 7, 9))
+			val iter = set.iterator()
+			check(iter.hasNext())
+			checkThrows<IllegalStateException> {
+				iter.remove()
+			}
+		}
+
+		test("Cannot remove an item twice") {
+			val set = create(arrayOf(5, 7, 9))
+			println("Iterating through set $set")
+			val iter = set.iterator()
+
+			check(iter.hasNext())
+			check(iter.next() == 5)
+			iter.remove()
+
+			checkThrows<IllegalStateException> {
+				iter.remove()
+			}
+		}
 	}
 
 	suite("retainAll") {
-- 
2.51.2