From 098c544fd8a9b7ff8be2892c1c833a63ddd5432e Mon Sep 17 00:00:00 2001
From: prozolic <42107886+prozolic@users.noreply.github.com>
Date: Sun, 22 Mar 2026 15:59:50 +0900
Subject: [PATCH] Add null check ImmutableArray<T>.Builder.RemoveAll

ImmutableArray<T>.Builder.RemoveAll(Predicate<T>) was missing a null
check on the `match` parameter. Passing null would throw
NullReferenceException or no exception instead of ArgumentNullException.

Add Requires.NotNull for the `match` parameter, and add a test case
to verify that null throws ArgumentNullException.
---
 .../System/Collections/Immutable/ImmutableArray_1.Builder.cs    | 2 ++
 .../tests/ImmutableArrayBuilderTest.cs                          | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableArray_1.Builder.cs b/src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableArray_1.Builder.cs
index 9f596e8f7578a7..4de80f12537927 100644
--- a/src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableArray_1.Builder.cs
+++ b/src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableArray_1.Builder.cs
@@ -540,6 +540,8 @@ public bool Remove(T element, IEqualityComparer<T>? equalityComparer)
             /// </param>
             public void RemoveAll(Predicate<T> match)
             {
+                Requires.NotNull(match, nameof(match));
+
                 List<int>? removeIndices = null;
                 for (int i = 0; i < _count; i++)
                 {
diff --git a/src/libraries/System.Collections.Immutable/tests/ImmutableArrayBuilderTest.cs b/src/libraries/System.Collections.Immutable/tests/ImmutableArrayBuilderTest.cs
index 841bfc451e332d..df05ab75b25d99 100644
--- a/src/libraries/System.Collections.Immutable/tests/ImmutableArrayBuilderTest.cs
+++ b/src/libraries/System.Collections.Immutable/tests/ImmutableArrayBuilderTest.cs
@@ -413,6 +413,8 @@ public void RemoveAll()
             builder.RemoveAll(n => n % 2 == 0);
 
             Assert.Equal(new[] { 1, 3, 5, 7 }, builder);
+
+            AssertExtensions.Throws<ArgumentNullException>("match", () => builder.RemoveAll(match: null));
         }
 
         [Fact]