From ea76501f9e0337ce6906b72bac9d1ca84e83775e Mon Sep 17 00:00:00 2001
From: Igor Yakovlev <igor.yakovlev@jetbrains.com>
Date: Thu, 27 Jan 2022 15:53:42 +0100
Subject: [PATCH] [WASM] Implement ConstrainedOnceSequence

---
 libraries/stdlib/wasm/src/kotlin/Sequences.kt | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/libraries/stdlib/wasm/src/kotlin/Sequences.kt b/libraries/stdlib/wasm/src/kotlin/Sequences.kt
index 01e51c5d714..e8306fe4273 100644
--- a/libraries/stdlib/wasm/src/kotlin/Sequences.kt
+++ b/libraries/stdlib/wasm/src/kotlin/Sequences.kt
@@ -5,8 +5,12 @@
 
 package kotlin.sequences
 
-internal actual class ConstrainedOnceSequence<T> : Sequence<T> {
-    actual constructor(sequence: Sequence<T>) { TODO("Wasm stdlib: ConstrainedOnceSequence") }
+internal actual class ConstrainedOnceSequence<T> actual constructor(sequence: Sequence<T>) : Sequence<T> {
+    private var sequenceRef: Sequence<T>? = sequence
 
-    actual override fun iterator(): Iterator<T> = TODO("Wasm stdlib: ConstrainedOnceSequence")
+    actual override fun iterator(): Iterator<T> {
+        val sequence = sequenceRef ?: throw IllegalStateException("This sequence can be consumed only once.")
+        sequenceRef = null
+        return sequence.iterator()
+    }
 }