diff --git a/StyleCop.Analyzers/StyleCop.Analyzers/Helpers/ObjectPools/PooledObject`1.cs b/StyleCop.Analyzers/StyleCop.Analyzers/Helpers/ObjectPools/PooledObject`1.cs
index 3bc8b0822..aff5a5891 100644
--- a/StyleCop.Analyzers/StyleCop.Analyzers/Helpers/ObjectPools/PooledObject`1.cs
+++ b/StyleCop.Analyzers/StyleCop.Analyzers/Helpers/ObjectPools/PooledObject`1.cs
@@ -29,7 +29,7 @@ public PooledObject(ObjectPool<T> pool, Func<ObjectPool<T>, T> allocator, Action
             this.releaser = releaser;
         }
 
-        public T Object
+        public readonly T Object
         {
             get
             {
diff --git a/StyleCop.Analyzers/StyleCop.Analyzers/Helpers/TriviaHelper.cs b/StyleCop.Analyzers/StyleCop.Analyzers/Helpers/TriviaHelper.cs
index 5563cd920..9ad5a4eb6 100644
--- a/StyleCop.Analyzers/StyleCop.Analyzers/Helpers/TriviaHelper.cs
+++ b/StyleCop.Analyzers/StyleCop.Analyzers/Helpers/TriviaHelper.cs
@@ -522,7 +522,7 @@ private static int BinarySearch(SyntaxTriviaList leadingTrivia, SyntaxTrivia tri
         /// <summary>
         /// Helper class that merges two SyntaxTriviaLists with (hopefully) the lowest possible performance penalty.
         /// </summary>
-        internal struct DualTriviaListHelper : IReadOnlyList<SyntaxTrivia>
+        internal readonly struct DualTriviaListHelper : IReadOnlyList<SyntaxTrivia>
         {
             private readonly SyntaxTriviaList part1;
             private readonly int part1Count;
diff --git a/StyleCop.Analyzers/StyleCop.Analyzers/LightJson/JsonValue.cs b/StyleCop.Analyzers/StyleCop.Analyzers/LightJson/JsonValue.cs
index 842515c3c..10af037ab 100644
--- a/StyleCop.Analyzers/StyleCop.Analyzers/LightJson/JsonValue.cs
+++ b/StyleCop.Analyzers/StyleCop.Analyzers/LightJson/JsonValue.cs
@@ -151,7 +151,7 @@ private JsonValue(JsonValueType type, double value, object reference)
         /// Gets the type of this JsonValue.
         /// </summary>
         /// <value>The type of this JsonValue.</value>
-        public JsonValueType Type
+        public readonly JsonValueType Type
         {
             get
             {
@@ -163,7 +163,7 @@ public JsonValueType Type
         /// Gets a value indicating whether this JsonValue is Null.
         /// </summary>
         /// <value>A value indicating whether this JsonValue is Null.</value>
-        public bool IsNull
+        public readonly bool IsNull
         {
             get
             {
@@ -175,7 +175,7 @@ public bool IsNull
         /// Gets a value indicating whether this JsonValue is a Boolean.
         /// </summary>
         /// <value>A value indicating whether this JsonValue is a Boolean.</value>
-        public bool IsBoolean
+        public readonly bool IsBoolean
         {
             get
             {
@@ -187,7 +187,7 @@ public bool IsBoolean
         /// Gets a value indicating whether this JsonValue is an Integer.
         /// </summary>
         /// <value>A value indicating whether this JsonValue is an Integer.</value>
-        public bool IsInteger
+        public readonly bool IsInteger
         {
             get
             {
@@ -205,7 +205,7 @@ public bool IsInteger
         /// Gets a value indicating whether this JsonValue is a Number.
         /// </summary>
         /// <value>A value indicating whether this JsonValue is a Number.</value>
-        public bool IsNumber
+        public readonly bool IsNumber
         {
             get
             {
@@ -217,7 +217,7 @@ public bool IsNumber
         /// Gets a value indicating whether this JsonValue is a String.
         /// </summary>
         /// <value>A value indicating whether this JsonValue is a String.</value>
-        public bool IsString
+        public readonly bool IsString
         {
             get
             {
@@ -229,7 +229,7 @@ public bool IsString
         /// Gets a value indicating whether this JsonValue is a JsonObject.
         /// </summary>
         /// <value>A value indicating whether this JsonValue is a JsonObject.</value>
-        public bool IsJsonObject
+        public readonly bool IsJsonObject
         {
             get
             {
@@ -241,7 +241,7 @@ public bool IsJsonObject
         /// Gets a value indicating whether this JsonValue is a JsonArray.
         /// </summary>
         /// <value>A value indicating whether this JsonValue is a JsonArray.</value>
-        public bool IsJsonArray
+        public readonly bool IsJsonArray
         {
             get
             {
@@ -253,7 +253,7 @@ public bool IsJsonArray
         /// Gets a value indicating whether this JsonValue represents a DateTime.
         /// </summary>
         /// <value>A value indicating whether this JsonValue represents a DateTime.</value>
-        public bool IsDateTime
+        public readonly bool IsDateTime
         {
             get
             {
@@ -265,7 +265,7 @@ public bool IsDateTime
         /// Gets a value indicating whether this value is true or false.
         /// </summary>
         /// <value>This value as a Boolean type.</value>
-        public bool AsBoolean
+        public readonly bool AsBoolean
         {
             get
             {
@@ -294,7 +294,7 @@ public bool AsBoolean
         /// Gets this value as an Integer type.
         /// </summary>
         /// <value>This value as an Integer type.</value>
-        public int AsInteger
+        public readonly int AsInteger
         {
             get
             {
@@ -319,7 +319,7 @@ public int AsInteger
         /// Gets this value as a Number type.
         /// </summary>
         /// <value>This value as a Number type.</value>
-        public double AsNumber
+        public readonly double AsNumber
         {
             get
             {
@@ -354,7 +354,7 @@ public double AsNumber
         /// Gets this value as a String type.
         /// </summary>
         /// <value>This value as a String type.</value>
-        public string AsString
+        public readonly string AsString
         {
             get
             {
@@ -381,7 +381,7 @@ public string AsString
         /// Gets this value as an JsonObject.
         /// </summary>
         /// <value>This value as an JsonObject.</value>
-        public JsonObject AsJsonObject
+        public readonly JsonObject AsJsonObject
         {
             get
             {
@@ -395,7 +395,7 @@ public JsonObject AsJsonObject
         /// Gets this value as an JsonArray.
         /// </summary>
         /// <value>This value as an JsonArray.</value>
-        public JsonArray AsJsonArray
+        public readonly JsonArray AsJsonArray
         {
             get
             {
@@ -409,7 +409,7 @@ public JsonArray AsJsonArray
         /// Gets this value as a system.DateTime.
         /// </summary>
         /// <value>This value as a system.DateTime.</value>
-        public DateTime? AsDateTime
+        public readonly DateTime? AsDateTime
         {
             get
             {
@@ -430,7 +430,7 @@ public DateTime? AsDateTime
         /// Gets this (inner) value as a System.object.
         /// </summary>
         /// <value>This (inner) value as a System.object.</value>
-        public object AsObject
+        public readonly object AsObject
         {
             get
             {
@@ -458,7 +458,7 @@ public object AsObject
         /// <exception cref="System.InvalidOperationException">
         /// Thrown when this JsonValue is not a JsonObject.
         /// </exception>
-        public JsonValue this[string key]
+        public readonly JsonValue this[string key]
         {
             get
             {
@@ -492,7 +492,7 @@ public JsonValue this[string key]
         /// <exception cref="InvalidOperationException">
         /// Thrown when this <see cref="JsonValue"/> is not a <see cref="JsonArray"/>.
         /// </exception>
-        public JsonValue this[int index]
+        public readonly JsonValue this[int index]
         {
             get
             {
@@ -813,7 +813,7 @@ public static JsonValue Parse(string text)
         }
 
         /// <inheritdoc/>
-        public override bool Equals(object obj)
+        public override readonly bool Equals(object obj)
         {
             if (obj == null)
             {
@@ -832,7 +832,7 @@ public override bool Equals(object obj)
         }
 
         /// <inheritdoc/>
-        public override int GetHashCode()
+        public override readonly int GetHashCode()
         {
             if (this.IsNull)
             {
diff --git a/StyleCop.Analyzers/StyleCop.Analyzers/Lightup/SeparatedSyntaxListWrapper`1.cs b/StyleCop.Analyzers/StyleCop.Analyzers/Lightup/SeparatedSyntaxListWrapper`1.cs
index 3e7f2f000..7e2cd4669 100644
--- a/StyleCop.Analyzers/StyleCop.Analyzers/Lightup/SeparatedSyntaxListWrapper`1.cs
+++ b/StyleCop.Analyzers/StyleCop.Analyzers/Lightup/SeparatedSyntaxListWrapper`1.cs
@@ -172,11 +172,11 @@ public Enumerator(SeparatedSyntaxListWrapper<TNode> wrapper)
                 this.current = default;
             }
 
-            public TNode Current => this.current;
+            public readonly TNode Current => this.current;
 
-            object IEnumerator.Current => this.Current;
+            readonly object IEnumerator.Current => this.Current;
 
-            public override bool Equals(object obj)
+            public override readonly bool Equals(object obj)
             {
                 Enumerator? otherOpt = obj as Enumerator?;
                 if (!otherOpt.HasValue)
@@ -189,7 +189,7 @@ public override bool Equals(object obj)
                     && other.index == this.index;
             }
 
-            public override int GetHashCode()
+            public override readonly int GetHashCode()
             {
                 if (this.wrapper == null)
                 {
@@ -199,7 +199,7 @@ public override int GetHashCode()
                 return this.wrapper.GetHashCode() ^ this.index;
             }
 
-            public void Dispose()
+            public readonly void Dispose()
             {
             }
 
diff --git a/StyleCop.Analyzers/StyleCopTester/Program.cs b/StyleCop.Analyzers/StyleCopTester/Program.cs
index a259cded4..0ad1b99b6 100644
--- a/StyleCop.Analyzers/StyleCopTester/Program.cs
+++ b/StyleCop.Analyzers/StyleCopTester/Program.cs
@@ -608,7 +608,7 @@ private static void PrintHelp()
             Console.WriteLine("/edititer:<iterations>  Specifies the number of iterations to use for testing documents with /editperf. When this is not specified, the default value is 10.");
         }
 
-        private struct DocumentAnalyzerPerformance
+        private readonly struct DocumentAnalyzerPerformance
         {
             public DocumentAnalyzerPerformance(double editsPerSecond)
             {
diff --git a/StyleCop.Analyzers/StyleCopTester/Statistic.cs b/StyleCop.Analyzers/StyleCopTester/Statistic.cs
index bb7151a07..432308d7e 100644
--- a/StyleCop.Analyzers/StyleCopTester/Statistic.cs
+++ b/StyleCop.Analyzers/StyleCopTester/Statistic.cs
@@ -5,7 +5,7 @@
 
 namespace StyleCopTester
 {
-    internal struct Statistic
+    internal readonly struct Statistic
     {
         public Statistic(int numberOfNodes, int numberOfTokens, int numberOfTrivia)
         {