diff --git a/src/libraries/System.Collections.Specialized/ref/System.Collections.Specialized.cs b/src/libraries/System.Collections.Specialized/ref/System.Collections.Specialized.cs
index 45ea7f1f33c5a..d998213a7c8d8 100644
--- a/src/libraries/System.Collections.Specialized/ref/System.Collections.Specialized.cs
+++ b/src/libraries/System.Collections.Specialized/ref/System.Collections.Specialized.cs
@@ -25,7 +25,7 @@ public partial struct BitVector32
         public override string ToString() { throw null; }
         public static string ToString(System.Collections.Specialized.BitVector32 value) { throw null; }
         [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-        public partial struct Section
+        public readonly partial struct Section
         {
             public short Mask { get { throw null; } }
             public short Offset { get { throw null; } }
diff --git a/src/libraries/System.ComponentModel.TypeConverter/ref/System.ComponentModel.cs b/src/libraries/System.ComponentModel.TypeConverter/ref/System.ComponentModel.cs
index 2a6ada4171fd3..4611ef0189e26 100644
--- a/src/libraries/System.ComponentModel.TypeConverter/ref/System.ComponentModel.cs
+++ b/src/libraries/System.ComponentModel.TypeConverter/ref/System.ComponentModel.cs
@@ -1438,7 +1438,7 @@ public InstanceDescriptor(System.Reflection.MemberInfo member, System.Collection
         public object Invoke() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MemberRelationship
+    public readonly partial struct MemberRelationship
     {
         public static readonly System.ComponentModel.Design.Serialization.MemberRelationship Empty;
         public MemberRelationship(object owner, System.ComponentModel.MemberDescriptor member) { throw null; }
diff --git a/src/libraries/System.Console/ref/System.Console.cs b/src/libraries/System.Console/ref/System.Console.cs
index 21432d702672e..358aea1b61d4d 100644
--- a/src/libraries/System.Console/ref/System.Console.cs
+++ b/src/libraries/System.Console/ref/System.Console.cs
@@ -127,7 +127,7 @@ public enum ConsoleColor
         White = 15,
         Yellow = 14,
     }
-    public partial struct ConsoleKeyInfo
+    public readonly partial struct ConsoleKeyInfo
     {
         public ConsoleKeyInfo(char keyChar, ConsoleKey key, bool shift, bool alt, bool control) { }
         public char KeyChar { get { throw null; } }
diff --git a/src/libraries/System.Diagnostics.PerformanceCounter/ref/System.Diagnostics.PerformanceCounter.cs b/src/libraries/System.Diagnostics.PerformanceCounter/ref/System.Diagnostics.PerformanceCounter.cs
index 802cb179ff831..611ab57f96e81 100644
--- a/src/libraries/System.Diagnostics.PerformanceCounter/ref/System.Diagnostics.PerformanceCounter.cs
+++ b/src/libraries/System.Diagnostics.PerformanceCounter/ref/System.Diagnostics.PerformanceCounter.cs
@@ -32,7 +32,7 @@ protected override void OnValidate(object value) { }
         public virtual void Remove(System.Diagnostics.CounterCreationData value) { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CounterSample
+    public readonly partial struct CounterSample
     {
         public static System.Diagnostics.CounterSample Empty;
         public CounterSample(long rawValue, long baseValue, long counterFrequency, long systemFrequency, long timeStamp, long timeStamp100nSec, System.Diagnostics.PerformanceCounterType counterType) { throw null;}
diff --git a/src/libraries/System.Diagnostics.StackTrace/ref/System.Diagnostics.StackTrace.cs b/src/libraries/System.Diagnostics.StackTrace/ref/System.Diagnostics.StackTrace.cs
index 1fe3c34c054af..f7e68daac5c48 100644
--- a/src/libraries/System.Diagnostics.StackTrace/ref/System.Diagnostics.StackTrace.cs
+++ b/src/libraries/System.Diagnostics.StackTrace/ref/System.Diagnostics.StackTrace.cs
@@ -173,7 +173,7 @@ public enum SymAddressKind
         NativeStackRegister = 8,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct SymbolToken
+    public readonly partial struct SymbolToken
     {
         public SymbolToken(int val) { throw null; }
         public bool Equals(System.Diagnostics.SymbolStore.SymbolToken obj) { throw null; }
diff --git a/src/libraries/System.Drawing.Primitives/ref/System.Drawing.Primitives.cs b/src/libraries/System.Drawing.Primitives/ref/System.Drawing.Primitives.cs
index 637125399723d..c4f3334a4a6d9 100644
--- a/src/libraries/System.Drawing.Primitives/ref/System.Drawing.Primitives.cs
+++ b/src/libraries/System.Drawing.Primitives/ref/System.Drawing.Primitives.cs
@@ -7,7 +7,7 @@
 
 namespace System.Drawing
 {
-    public partial struct Color : System.IEquatable<System.Drawing.Color>
+    public readonly partial struct Color : System.IEquatable<System.Drawing.Color>
     {
         public static readonly System.Drawing.Color Empty;
         public byte A { get { throw null; } }
diff --git a/src/libraries/System.Net.Security/ref/System.Net.Security.cs b/src/libraries/System.Net.Security/ref/System.Net.Security.cs
index b47abcf906f6d..46e8b3061f916 100644
--- a/src/libraries/System.Net.Security/ref/System.Net.Security.cs
+++ b/src/libraries/System.Net.Security/ref/System.Net.Security.cs
@@ -122,7 +122,7 @@ public partial class SslClientAuthenticationOptions
         public RemoteCertificateValidationCallback RemoteCertificateValidationCallback { get { throw null; } set { } }
         public EncryptionPolicy EncryptionPolicy { get { throw null; } set { } }
     }
-    public partial struct SslApplicationProtocol : IEquatable<SslApplicationProtocol>
+    public readonly partial struct SslApplicationProtocol : IEquatable<SslApplicationProtocol>
     {
         public static readonly SslApplicationProtocol Http2;
         public static readonly SslApplicationProtocol Http11;
diff --git a/src/libraries/System.Reflection.Metadata/ref/System.Reflection.Metadata.cs b/src/libraries/System.Reflection.Metadata/ref/System.Reflection.Metadata.cs
index 507b479bf6a15..229f5bc67bb36 100644
--- a/src/libraries/System.Reflection.Metadata/ref/System.Reflection.Metadata.cs
+++ b/src/libraries/System.Reflection.Metadata/ref/System.Reflection.Metadata.cs
@@ -83,7 +83,7 @@ public enum MethodSemanticsAttributes
 namespace System.Reflection.Metadata
 {
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ArrayShape
+    public readonly partial struct ArrayShape
     {
         public ArrayShape(int rank, System.Collections.Immutable.ImmutableArray<int> sizes, System.Collections.Immutable.ImmutableArray<int> lowerBounds) { throw null;}
         public System.Collections.Immutable.ImmutableArray<int> LowerBounds { get { throw null; } }
@@ -91,7 +91,7 @@ public partial struct ArrayShape
         public System.Collections.Immutable.ImmutableArray<int> Sizes { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct AssemblyDefinition
+    public readonly partial struct AssemblyDefinition
     {
         public System.Reflection.Metadata.StringHandle Culture { get { throw null; } }
         public System.Reflection.AssemblyFlags Flags { get { throw null; } }
@@ -106,7 +106,7 @@ public partial struct AssemblyDefinition
         public System.Reflection.Metadata.DeclarativeSecurityAttributeHandleCollection GetDeclarativeSecurityAttributes() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct AssemblyDefinitionHandle : System.IEquatable<System.Reflection.Metadata.AssemblyDefinitionHandle>
+    public readonly partial struct AssemblyDefinitionHandle : System.IEquatable<System.Reflection.Metadata.AssemblyDefinitionHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -120,7 +120,7 @@ public partial struct AssemblyDefinitionHandle : System.IEquatable<System.Reflec
         public static bool operator !=(System.Reflection.Metadata.AssemblyDefinitionHandle left, System.Reflection.Metadata.AssemblyDefinitionHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct AssemblyFile
+    public readonly partial struct AssemblyFile
     {
         public bool ContainsMetadata { get { throw null; } }
         public System.Reflection.Metadata.BlobHandle HashValue { get { throw null; } }
@@ -128,7 +128,7 @@ public partial struct AssemblyFile
         public System.Reflection.Metadata.CustomAttributeHandleCollection GetCustomAttributes() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct AssemblyFileHandle : System.IEquatable<System.Reflection.Metadata.AssemblyFileHandle>
+    public readonly partial struct AssemblyFileHandle : System.IEquatable<System.Reflection.Metadata.AssemblyFileHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -142,7 +142,7 @@ public partial struct AssemblyFileHandle : System.IEquatable<System.Reflection.M
         public static bool operator !=(System.Reflection.Metadata.AssemblyFileHandle left, System.Reflection.Metadata.AssemblyFileHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct AssemblyFileHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.AssemblyFileHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.AssemblyFileHandle>, System.Collections.IEnumerable
+    public readonly partial struct AssemblyFileHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.AssemblyFileHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.AssemblyFileHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.AssemblyFileHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -159,7 +159,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct AssemblyReference
+    public readonly partial struct AssemblyReference
     {
         public System.Reflection.Metadata.StringHandle Culture { get { throw null; } }
         public System.Reflection.AssemblyFlags Flags { get { throw null; } }
@@ -173,7 +173,7 @@ public partial struct AssemblyReference
         public System.Reflection.Metadata.CustomAttributeHandleCollection GetCustomAttributes() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct AssemblyReferenceHandle : System.IEquatable<System.Reflection.Metadata.AssemblyReferenceHandle>
+    public readonly partial struct AssemblyReferenceHandle : System.IEquatable<System.Reflection.Metadata.AssemblyReferenceHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -187,7 +187,7 @@ public partial struct AssemblyReferenceHandle : System.IEquatable<System.Reflect
         public static bool operator !=(System.Reflection.Metadata.AssemblyReferenceHandle left, System.Reflection.Metadata.AssemblyReferenceHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct AssemblyReferenceHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.AssemblyReferenceHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.AssemblyReferenceHandle>, System.Collections.IEnumerable
+    public readonly partial struct AssemblyReferenceHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.AssemblyReferenceHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.AssemblyReferenceHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.AssemblyReferenceHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -204,7 +204,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct Blob
+    public readonly partial struct Blob
     {
         public bool IsDefault { get { throw null; } }
         public int Length { get { throw null; } }
@@ -282,7 +282,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct BlobContentId : System.IEquatable<System.Reflection.Metadata.BlobContentId>
+    public readonly partial struct BlobContentId : System.IEquatable<System.Reflection.Metadata.BlobContentId>
     {
         public BlobContentId(byte[] id) { throw null;}
         public BlobContentId(System.Collections.Immutable.ImmutableArray<byte> id) { throw null;}
@@ -300,7 +300,7 @@ public partial struct BlobContentId : System.IEquatable<System.Reflection.Metada
         public static bool operator !=(System.Reflection.Metadata.BlobContentId left, System.Reflection.Metadata.BlobContentId right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct BlobHandle : System.IEquatable<System.Reflection.Metadata.BlobHandle>
+    public readonly partial struct BlobHandle : System.IEquatable<System.Reflection.Metadata.BlobHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -410,14 +410,14 @@ public void WriteUTF16(string value) { }
         public void WriteUTF8(string value, bool allowUnpairedSurrogates) { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct Constant
+    public readonly partial struct Constant
     {
         public System.Reflection.Metadata.EntityHandle Parent { get { throw null; } }
         public System.Reflection.Metadata.ConstantTypeCode TypeCode { get { throw null; } }
         public System.Reflection.Metadata.BlobHandle Value { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ConstantHandle : System.IEquatable<System.Reflection.Metadata.ConstantHandle>
+    public readonly partial struct ConstantHandle : System.IEquatable<System.Reflection.Metadata.ConstantHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -449,7 +449,7 @@ public enum ConstantTypeCode : byte
         UInt64 = (byte)11,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CustomAttribute
+    public readonly partial struct CustomAttribute
     {
         public System.Reflection.Metadata.EntityHandle Constructor { get { throw null; } }
         public System.Reflection.Metadata.EntityHandle Parent { get { throw null; } }
@@ -457,7 +457,7 @@ public partial struct CustomAttribute
         public System.Reflection.Metadata.CustomAttributeValue<TType> DecodeValue<TType>(System.Reflection.Metadata.ICustomAttributeTypeProvider<TType> provider) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CustomAttributeHandle : System.IEquatable<System.Reflection.Metadata.CustomAttributeHandle>
+    public readonly partial struct CustomAttributeHandle : System.IEquatable<System.Reflection.Metadata.CustomAttributeHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -471,7 +471,7 @@ public partial struct CustomAttributeHandle : System.IEquatable<System.Reflectio
         public static bool operator !=(System.Reflection.Metadata.CustomAttributeHandle left, System.Reflection.Metadata.CustomAttributeHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CustomAttributeHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.CustomAttributeHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.CustomAttributeHandle>, System.Collections.IEnumerable
+    public readonly partial struct CustomAttributeHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.CustomAttributeHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.CustomAttributeHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.CustomAttributeHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -493,7 +493,7 @@ public enum CustomAttributeNamedArgumentKind : byte
         Property = (byte)84,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CustomAttributeNamedArgument<TType>
+    public readonly partial struct CustomAttributeNamedArgument<TType>
     {
         public CustomAttributeNamedArgument(string name, System.Reflection.Metadata.CustomAttributeNamedArgumentKind kind, TType type, object value) { throw null;}
         public System.Reflection.Metadata.CustomAttributeNamedArgumentKind Kind { get { throw null; } }
@@ -502,28 +502,28 @@ public partial struct CustomAttributeNamedArgument<TType>
         public object Value { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CustomAttributeTypedArgument<TType>
+    public readonly partial struct CustomAttributeTypedArgument<TType>
     {
         public CustomAttributeTypedArgument(TType type, object value) { throw null;}
         public TType Type { get { throw null; } }
         public object Value { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CustomAttributeValue<TType>
+    public readonly partial struct CustomAttributeValue<TType>
     {
         public CustomAttributeValue(System.Collections.Immutable.ImmutableArray<System.Reflection.Metadata.CustomAttributeTypedArgument<TType>> fixedArguments, System.Collections.Immutable.ImmutableArray<System.Reflection.Metadata.CustomAttributeNamedArgument<TType>> namedArguments) { throw null;}
         public System.Collections.Immutable.ImmutableArray<System.Reflection.Metadata.CustomAttributeTypedArgument<TType>> FixedArguments { get { throw null; } }
         public System.Collections.Immutable.ImmutableArray<System.Reflection.Metadata.CustomAttributeNamedArgument<TType>> NamedArguments { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CustomDebugInformation
+    public readonly partial struct CustomDebugInformation
     {
         public System.Reflection.Metadata.GuidHandle Kind { get { throw null; } }
         public System.Reflection.Metadata.EntityHandle Parent { get { throw null; } }
         public System.Reflection.Metadata.BlobHandle Value { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CustomDebugInformationHandle : System.IEquatable<System.Reflection.Metadata.CustomDebugInformationHandle>
+    public readonly partial struct CustomDebugInformationHandle : System.IEquatable<System.Reflection.Metadata.CustomDebugInformationHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -537,7 +537,7 @@ public partial struct CustomDebugInformationHandle : System.IEquatable<System.Re
         public static bool operator !=(System.Reflection.Metadata.CustomDebugInformationHandle left, System.Reflection.Metadata.CustomDebugInformationHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CustomDebugInformationHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.CustomDebugInformationHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.CustomDebugInformationHandle>, System.Collections.IEnumerable
+    public readonly partial struct CustomDebugInformationHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.CustomDebugInformationHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.CustomDebugInformationHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.CustomDebugInformationHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -560,14 +560,14 @@ internal DebugMetadataHeader() { }
         public System.Collections.Immutable.ImmutableArray<byte> Id { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct DeclarativeSecurityAttribute
+    public readonly partial struct DeclarativeSecurityAttribute
     {
         public System.Reflection.DeclarativeSecurityAction Action { get { throw null; } }
         public System.Reflection.Metadata.EntityHandle Parent { get { throw null; } }
         public System.Reflection.Metadata.BlobHandle PermissionSet { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct DeclarativeSecurityAttributeHandle : System.IEquatable<System.Reflection.Metadata.DeclarativeSecurityAttributeHandle>
+    public readonly partial struct DeclarativeSecurityAttributeHandle : System.IEquatable<System.Reflection.Metadata.DeclarativeSecurityAttributeHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -581,7 +581,7 @@ public partial struct DeclarativeSecurityAttributeHandle : System.IEquatable<Sys
         public static bool operator !=(System.Reflection.Metadata.DeclarativeSecurityAttributeHandle left, System.Reflection.Metadata.DeclarativeSecurityAttributeHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct DeclarativeSecurityAttributeHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.DeclarativeSecurityAttributeHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.DeclarativeSecurityAttributeHandle>, System.Collections.IEnumerable
+    public readonly partial struct DeclarativeSecurityAttributeHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.DeclarativeSecurityAttributeHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.DeclarativeSecurityAttributeHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.DeclarativeSecurityAttributeHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -598,7 +598,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct Document
+    public readonly partial struct Document
     {
         public System.Reflection.Metadata.BlobHandle Hash { get { throw null; } }
         public System.Reflection.Metadata.GuidHandle HashAlgorithm { get { throw null; } }
@@ -606,7 +606,7 @@ public partial struct Document
         public System.Reflection.Metadata.DocumentNameBlobHandle Name { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct DocumentHandle : System.IEquatable<System.Reflection.Metadata.DocumentHandle>
+    public readonly partial struct DocumentHandle : System.IEquatable<System.Reflection.Metadata.DocumentHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -620,7 +620,7 @@ public partial struct DocumentHandle : System.IEquatable<System.Reflection.Metad
         public static bool operator !=(System.Reflection.Metadata.DocumentHandle left, System.Reflection.Metadata.DocumentHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct DocumentHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.DocumentHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.DocumentHandle>, System.Collections.IEnumerable
+    public readonly partial struct DocumentHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.DocumentHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.DocumentHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.DocumentHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -637,7 +637,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct DocumentNameBlobHandle : System.IEquatable<System.Reflection.Metadata.DocumentNameBlobHandle>
+    public readonly partial struct DocumentNameBlobHandle : System.IEquatable<System.Reflection.Metadata.DocumentNameBlobHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -649,7 +649,7 @@ public partial struct DocumentNameBlobHandle : System.IEquatable<System.Reflecti
         public static bool operator !=(System.Reflection.Metadata.DocumentNameBlobHandle left, System.Reflection.Metadata.DocumentNameBlobHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct EntityHandle : System.IEquatable<System.Reflection.Metadata.EntityHandle>
+    public readonly partial struct EntityHandle : System.IEquatable<System.Reflection.Metadata.EntityHandle>
     {
         public static readonly System.Reflection.Metadata.AssemblyDefinitionHandle AssemblyDefinition;
         public static readonly System.Reflection.Metadata.ModuleDefinitionHandle ModuleDefinition;
@@ -664,14 +664,14 @@ public partial struct EntityHandle : System.IEquatable<System.Reflection.Metadat
         public static bool operator !=(System.Reflection.Metadata.EntityHandle left, System.Reflection.Metadata.EntityHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct EventAccessors
+    public readonly partial struct EventAccessors
     {
         public System.Reflection.Metadata.MethodDefinitionHandle Adder { get { throw null; } }
         public System.Reflection.Metadata.MethodDefinitionHandle Raiser { get { throw null; } }
         public System.Reflection.Metadata.MethodDefinitionHandle Remover { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct EventDefinition
+    public readonly partial struct EventDefinition
     {
         public System.Reflection.EventAttributes Attributes { get { throw null; } }
         public System.Reflection.Metadata.StringHandle Name { get { throw null; } }
@@ -680,7 +680,7 @@ public partial struct EventDefinition
         public System.Reflection.Metadata.CustomAttributeHandleCollection GetCustomAttributes() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct EventDefinitionHandle : System.IEquatable<System.Reflection.Metadata.EventDefinitionHandle>
+    public readonly partial struct EventDefinitionHandle : System.IEquatable<System.Reflection.Metadata.EventDefinitionHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -694,7 +694,7 @@ public partial struct EventDefinitionHandle : System.IEquatable<System.Reflectio
         public static bool operator !=(System.Reflection.Metadata.EventDefinitionHandle left, System.Reflection.Metadata.EventDefinitionHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct EventDefinitionHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.EventDefinitionHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.EventDefinitionHandle>, System.Collections.IEnumerable
+    public readonly partial struct EventDefinitionHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.EventDefinitionHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.EventDefinitionHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.EventDefinitionHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -711,7 +711,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ExceptionRegion
+    public readonly partial struct ExceptionRegion
     {
         public System.Reflection.Metadata.EntityHandle CatchType { get { throw null; } }
         public int FilterOffset { get { throw null; } }
@@ -729,7 +729,7 @@ public enum ExceptionRegionKind : ushort
         Finally = (ushort)2,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ExportedType
+    public readonly partial struct ExportedType
     {
         public System.Reflection.TypeAttributes Attributes { get { throw null; } }
         public System.Reflection.Metadata.EntityHandle Implementation { get { throw null; } }
@@ -740,7 +740,7 @@ public partial struct ExportedType
         public System.Reflection.Metadata.CustomAttributeHandleCollection GetCustomAttributes() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ExportedTypeHandle : System.IEquatable<System.Reflection.Metadata.ExportedTypeHandle>
+    public readonly partial struct ExportedTypeHandle : System.IEquatable<System.Reflection.Metadata.ExportedTypeHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -754,7 +754,7 @@ public partial struct ExportedTypeHandle : System.IEquatable<System.Reflection.M
         public static bool operator !=(System.Reflection.Metadata.ExportedTypeHandle left, System.Reflection.Metadata.ExportedTypeHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ExportedTypeHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.ExportedTypeHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.ExportedTypeHandle>, System.Collections.IEnumerable
+    public readonly partial struct ExportedTypeHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.ExportedTypeHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.ExportedTypeHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.ExportedTypeHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -771,7 +771,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct FieldDefinition
+    public readonly partial struct FieldDefinition
     {
         public System.Reflection.FieldAttributes Attributes { get { throw null; } }
         public System.Reflection.Metadata.StringHandle Name { get { throw null; } }
@@ -785,7 +785,7 @@ public partial struct FieldDefinition
         public int GetRelativeVirtualAddress() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct FieldDefinitionHandle : System.IEquatable<System.Reflection.Metadata.FieldDefinitionHandle>
+    public readonly partial struct FieldDefinitionHandle : System.IEquatable<System.Reflection.Metadata.FieldDefinitionHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -799,7 +799,7 @@ public partial struct FieldDefinitionHandle : System.IEquatable<System.Reflectio
         public static bool operator !=(System.Reflection.Metadata.FieldDefinitionHandle left, System.Reflection.Metadata.FieldDefinitionHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct FieldDefinitionHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.FieldDefinitionHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.FieldDefinitionHandle>, System.Collections.IEnumerable
+    public readonly partial struct FieldDefinitionHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.FieldDefinitionHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.FieldDefinitionHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.FieldDefinitionHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -816,7 +816,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct GenericParameter
+    public readonly partial struct GenericParameter
     {
         public System.Reflection.GenericParameterAttributes Attributes { get { throw null; } }
         public int Index { get { throw null; } }
@@ -826,14 +826,14 @@ public partial struct GenericParameter
         public System.Reflection.Metadata.CustomAttributeHandleCollection GetCustomAttributes() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct GenericParameterConstraint
+    public readonly partial struct GenericParameterConstraint
     {
         public System.Reflection.Metadata.GenericParameterHandle Parameter { get { throw null; } }
         public System.Reflection.Metadata.EntityHandle Type { get { throw null; } }
         public System.Reflection.Metadata.CustomAttributeHandleCollection GetCustomAttributes() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct GenericParameterConstraintHandle : System.IEquatable<System.Reflection.Metadata.GenericParameterConstraintHandle>
+    public readonly partial struct GenericParameterConstraintHandle : System.IEquatable<System.Reflection.Metadata.GenericParameterConstraintHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -847,7 +847,7 @@ public partial struct GenericParameterConstraintHandle : System.IEquatable<Syste
         public static bool operator !=(System.Reflection.Metadata.GenericParameterConstraintHandle left, System.Reflection.Metadata.GenericParameterConstraintHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct GenericParameterConstraintHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.GenericParameterConstraintHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.GenericParameterConstraintHandle>, System.Collections.Generic.IReadOnlyList<System.Reflection.Metadata.GenericParameterConstraintHandle>, System.Collections.IEnumerable
+    public readonly partial struct GenericParameterConstraintHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.GenericParameterConstraintHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.GenericParameterConstraintHandle>, System.Collections.Generic.IReadOnlyList<System.Reflection.Metadata.GenericParameterConstraintHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.GenericParameterConstraintHandle this[int index] { get { throw null; } }
@@ -865,7 +865,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct GenericParameterHandle : System.IEquatable<System.Reflection.Metadata.GenericParameterHandle>
+    public readonly partial struct GenericParameterHandle : System.IEquatable<System.Reflection.Metadata.GenericParameterHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -879,7 +879,7 @@ public partial struct GenericParameterHandle : System.IEquatable<System.Reflecti
         public static bool operator !=(System.Reflection.Metadata.GenericParameterHandle left, System.Reflection.Metadata.GenericParameterHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct GenericParameterHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.GenericParameterHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.GenericParameterHandle>, System.Collections.Generic.IReadOnlyList<System.Reflection.Metadata.GenericParameterHandle>, System.Collections.IEnumerable
+    public readonly partial struct GenericParameterHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.GenericParameterHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.GenericParameterHandle>, System.Collections.Generic.IReadOnlyList<System.Reflection.Metadata.GenericParameterHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.GenericParameterHandle this[int index] { get { throw null; } }
@@ -897,7 +897,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct GuidHandle : System.IEquatable<System.Reflection.Metadata.GuidHandle>
+    public readonly partial struct GuidHandle : System.IEquatable<System.Reflection.Metadata.GuidHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -909,7 +909,7 @@ public partial struct GuidHandle : System.IEquatable<System.Reflection.Metadata.
         public static bool operator !=(System.Reflection.Metadata.GuidHandle left, System.Reflection.Metadata.GuidHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct Handle : System.IEquatable<System.Reflection.Metadata.Handle>
+    public readonly partial struct Handle : System.IEquatable<System.Reflection.Metadata.Handle>
     {
         public static readonly System.Reflection.Metadata.AssemblyDefinitionHandle AssemblyDefinition;
         public static readonly System.Reflection.Metadata.ModuleDefinitionHandle ModuleDefinition;
@@ -1221,7 +1221,7 @@ public ImageFormatLimitationException(string message) { }
         public ImageFormatLimitationException(string message, System.Exception innerException) { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ImportDefinition
+    public readonly partial struct ImportDefinition
     {
         public System.Reflection.Metadata.BlobHandle Alias { get { throw null; } }
         public System.Reflection.Metadata.ImportDefinitionKind Kind { get { throw null; } }
@@ -1230,7 +1230,7 @@ public partial struct ImportDefinition
         public System.Reflection.Metadata.EntityHandle TargetType { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ImportDefinitionCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.ImportDefinition>, System.Collections.IEnumerable
+    public readonly partial struct ImportDefinitionCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.ImportDefinition>, System.Collections.IEnumerable
     {
         public System.Reflection.Metadata.ImportDefinitionCollection.Enumerator GetEnumerator() { throw null; }
         System.Collections.Generic.IEnumerator<System.Reflection.Metadata.ImportDefinition> System.Collections.Generic.IEnumerable<System.Reflection.Metadata.ImportDefinition>.GetEnumerator() { throw null; }
@@ -1258,14 +1258,14 @@ public enum ImportDefinitionKind
         ImportXmlNamespace = 4,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ImportScope
+    public readonly partial struct ImportScope
     {
         public System.Reflection.Metadata.BlobHandle ImportsBlob { get { throw null; } }
         public System.Reflection.Metadata.ImportScopeHandle Parent { get { throw null; } }
         public System.Reflection.Metadata.ImportDefinitionCollection GetImports() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ImportScopeCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.ImportScopeHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.ImportScopeHandle>, System.Collections.IEnumerable
+    public readonly partial struct ImportScopeCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.ImportScopeHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.ImportScopeHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.ImportScopeCollection.Enumerator GetEnumerator() { throw null; }
@@ -1282,7 +1282,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ImportScopeHandle : System.IEquatable<System.Reflection.Metadata.ImportScopeHandle>
+    public readonly partial struct ImportScopeHandle : System.IEquatable<System.Reflection.Metadata.ImportScopeHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1296,13 +1296,13 @@ public partial struct ImportScopeHandle : System.IEquatable<System.Reflection.Me
         public static bool operator !=(System.Reflection.Metadata.ImportScopeHandle left, System.Reflection.Metadata.ImportScopeHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct InterfaceImplementation
+    public readonly partial struct InterfaceImplementation
     {
         public System.Reflection.Metadata.EntityHandle Interface { get { throw null; } }
         public System.Reflection.Metadata.CustomAttributeHandleCollection GetCustomAttributes() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct InterfaceImplementationHandle : System.IEquatable<System.Reflection.Metadata.InterfaceImplementationHandle>
+    public readonly partial struct InterfaceImplementationHandle : System.IEquatable<System.Reflection.Metadata.InterfaceImplementationHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1316,7 +1316,7 @@ public partial struct InterfaceImplementationHandle : System.IEquatable<System.R
         public static bool operator !=(System.Reflection.Metadata.InterfaceImplementationHandle left, System.Reflection.Metadata.InterfaceImplementationHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct InterfaceImplementationHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.InterfaceImplementationHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.InterfaceImplementationHandle>, System.Collections.IEnumerable
+    public readonly partial struct InterfaceImplementationHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.InterfaceImplementationHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.InterfaceImplementationHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.InterfaceImplementationHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -1352,13 +1352,13 @@ public partial interface ISZArrayTypeProvider<TType>
         TType GetSZArrayType(TType elementType);
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct LocalConstant
+    public readonly partial struct LocalConstant
     {
         public System.Reflection.Metadata.StringHandle Name { get { throw null; } }
         public System.Reflection.Metadata.BlobHandle Signature { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct LocalConstantHandle : System.IEquatable<System.Reflection.Metadata.LocalConstantHandle>
+    public readonly partial struct LocalConstantHandle : System.IEquatable<System.Reflection.Metadata.LocalConstantHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1372,7 +1372,7 @@ public partial struct LocalConstantHandle : System.IEquatable<System.Reflection.
         public static bool operator !=(System.Reflection.Metadata.LocalConstantHandle left, System.Reflection.Metadata.LocalConstantHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct LocalConstantHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.LocalConstantHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.LocalConstantHandle>, System.Collections.IEnumerable
+    public readonly partial struct LocalConstantHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.LocalConstantHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.LocalConstantHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.LocalConstantHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -1389,7 +1389,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct LocalScope
+    public readonly partial struct LocalScope
     {
         public int EndOffset { get { throw null; } }
         public System.Reflection.Metadata.ImportScopeHandle ImportScope { get { throw null; } }
@@ -1401,7 +1401,7 @@ public partial struct LocalScope
         public System.Reflection.Metadata.LocalVariableHandleCollection GetLocalVariables() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct LocalScopeHandle : System.IEquatable<System.Reflection.Metadata.LocalScopeHandle>
+    public readonly partial struct LocalScopeHandle : System.IEquatable<System.Reflection.Metadata.LocalScopeHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1415,7 +1415,7 @@ public partial struct LocalScopeHandle : System.IEquatable<System.Reflection.Met
         public static bool operator !=(System.Reflection.Metadata.LocalScopeHandle left, System.Reflection.Metadata.LocalScopeHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct LocalScopeHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.LocalScopeHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.LocalScopeHandle>, System.Collections.IEnumerable
+    public readonly partial struct LocalScopeHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.LocalScopeHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.LocalScopeHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.LocalScopeHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -1441,7 +1441,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct LocalVariable
+    public readonly partial struct LocalVariable
     {
         public System.Reflection.Metadata.LocalVariableAttributes Attributes { get { throw null; } }
         public int Index { get { throw null; } }
@@ -1454,7 +1454,7 @@ public enum LocalVariableAttributes
         None = 0,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct LocalVariableHandle : System.IEquatable<System.Reflection.Metadata.LocalVariableHandle>
+    public readonly partial struct LocalVariableHandle : System.IEquatable<System.Reflection.Metadata.LocalVariableHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1468,7 +1468,7 @@ public partial struct LocalVariableHandle : System.IEquatable<System.Reflection.
         public static bool operator !=(System.Reflection.Metadata.LocalVariableHandle left, System.Reflection.Metadata.LocalVariableHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct LocalVariableHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.LocalVariableHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.LocalVariableHandle>, System.Collections.IEnumerable
+    public readonly partial struct LocalVariableHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.LocalVariableHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.LocalVariableHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.LocalVariableHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -1485,7 +1485,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ManifestResource
+    public readonly partial struct ManifestResource
     {
         public System.Reflection.ManifestResourceAttributes Attributes { get { throw null; } }
         public System.Reflection.Metadata.EntityHandle Implementation { get { throw null; } }
@@ -1494,7 +1494,7 @@ public partial struct ManifestResource
         public System.Reflection.Metadata.CustomAttributeHandleCollection GetCustomAttributes() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ManifestResourceHandle : System.IEquatable<System.Reflection.Metadata.ManifestResourceHandle>
+    public readonly partial struct ManifestResourceHandle : System.IEquatable<System.Reflection.Metadata.ManifestResourceHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1508,7 +1508,7 @@ public partial struct ManifestResourceHandle : System.IEquatable<System.Reflecti
         public static bool operator !=(System.Reflection.Metadata.ManifestResourceHandle left, System.Reflection.Metadata.ManifestResourceHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ManifestResourceHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.ManifestResourceHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.ManifestResourceHandle>, System.Collections.IEnumerable
+    public readonly partial struct ManifestResourceHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.ManifestResourceHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.ManifestResourceHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.ManifestResourceHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -1525,7 +1525,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MemberReference
+    public readonly partial struct MemberReference
     {
         public System.Reflection.Metadata.StringHandle Name { get { throw null; } }
         public System.Reflection.Metadata.EntityHandle Parent { get { throw null; } }
@@ -1536,7 +1536,7 @@ public partial struct MemberReference
         public System.Reflection.Metadata.MemberReferenceKind GetKind() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MemberReferenceHandle : System.IEquatable<System.Reflection.Metadata.MemberReferenceHandle>
+    public readonly partial struct MemberReferenceHandle : System.IEquatable<System.Reflection.Metadata.MemberReferenceHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1550,7 +1550,7 @@ public partial struct MemberReferenceHandle : System.IEquatable<System.Reflectio
         public static bool operator !=(System.Reflection.Metadata.MemberReferenceHandle left, System.Reflection.Metadata.MemberReferenceHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MemberReferenceHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.MemberReferenceHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.MemberReferenceHandle>, System.Collections.IEnumerable
+    public readonly partial struct MemberReferenceHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.MemberReferenceHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.MemberReferenceHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.MemberReferenceHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -1687,7 +1687,7 @@ public enum MetadataStreamOptions
         PrefetchMetadata = 2,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MetadataStringComparer
+    public readonly partial struct MetadataStringComparer
     {
         public bool Equals(System.Reflection.Metadata.DocumentNameBlobHandle handle, string value) { throw null; }
         public bool Equals(System.Reflection.Metadata.DocumentNameBlobHandle handle, string value, bool ignoreCase) { throw null; }
@@ -1719,7 +1719,7 @@ internal MethodBodyBlock() { }
         public System.Reflection.Metadata.BlobReader GetILReader() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodDebugInformation
+    public readonly partial struct MethodDebugInformation
     {
         public System.Reflection.Metadata.DocumentHandle Document { get { throw null; } }
         public System.Reflection.Metadata.StandaloneSignatureHandle LocalSignature { get { throw null; } }
@@ -1728,7 +1728,7 @@ public partial struct MethodDebugInformation
         public System.Reflection.Metadata.MethodDefinitionHandle GetStateMachineKickoffMethod() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodDebugInformationHandle : System.IEquatable<System.Reflection.Metadata.MethodDebugInformationHandle>
+    public readonly partial struct MethodDebugInformationHandle : System.IEquatable<System.Reflection.Metadata.MethodDebugInformationHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1743,7 +1743,7 @@ public partial struct MethodDebugInformationHandle : System.IEquatable<System.Re
         public System.Reflection.Metadata.MethodDefinitionHandle ToDefinitionHandle() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodDebugInformationHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.MethodDebugInformationHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.MethodDebugInformationHandle>, System.Collections.IEnumerable
+    public readonly partial struct MethodDebugInformationHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.MethodDebugInformationHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.MethodDebugInformationHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.MethodDebugInformationHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -1760,7 +1760,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodDefinition
+    public readonly partial struct MethodDefinition
     {
         public System.Reflection.MethodAttributes Attributes { get { throw null; } }
         public System.Reflection.MethodImplAttributes ImplAttributes { get { throw null; } }
@@ -1776,7 +1776,7 @@ public partial struct MethodDefinition
         public System.Reflection.Metadata.ParameterHandleCollection GetParameters() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodDefinitionHandle : System.IEquatable<System.Reflection.Metadata.MethodDefinitionHandle>
+    public readonly partial struct MethodDefinitionHandle : System.IEquatable<System.Reflection.Metadata.MethodDefinitionHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1791,7 +1791,7 @@ public partial struct MethodDefinitionHandle : System.IEquatable<System.Reflecti
         public System.Reflection.Metadata.MethodDebugInformationHandle ToDebugInformationHandle() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodDefinitionHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.MethodDefinitionHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.MethodDefinitionHandle>, System.Collections.IEnumerable
+    public readonly partial struct MethodDefinitionHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.MethodDefinitionHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.MethodDefinitionHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.MethodDefinitionHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -1808,7 +1808,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodImplementation
+    public readonly partial struct MethodImplementation
     {
         public System.Reflection.Metadata.EntityHandle MethodBody { get { throw null; } }
         public System.Reflection.Metadata.EntityHandle MethodDeclaration { get { throw null; } }
@@ -1816,7 +1816,7 @@ public partial struct MethodImplementation
         public System.Reflection.Metadata.CustomAttributeHandleCollection GetCustomAttributes() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodImplementationHandle : System.IEquatable<System.Reflection.Metadata.MethodImplementationHandle>
+    public readonly partial struct MethodImplementationHandle : System.IEquatable<System.Reflection.Metadata.MethodImplementationHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1830,7 +1830,7 @@ public partial struct MethodImplementationHandle : System.IEquatable<System.Refl
         public static bool operator !=(System.Reflection.Metadata.MethodImplementationHandle left, System.Reflection.Metadata.MethodImplementationHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodImplementationHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.MethodImplementationHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.MethodImplementationHandle>, System.Collections.IEnumerable
+    public readonly partial struct MethodImplementationHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.MethodImplementationHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.MethodImplementationHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.MethodImplementationHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -1847,14 +1847,14 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodImport
+    public readonly partial struct MethodImport
     {
         public System.Reflection.MethodImportAttributes Attributes { get { throw null; } }
         public System.Reflection.Metadata.ModuleReferenceHandle Module { get { throw null; } }
         public System.Reflection.Metadata.StringHandle Name { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodSignature<TType>
+    public readonly partial struct MethodSignature<TType>
     {
         public MethodSignature(System.Reflection.Metadata.SignatureHeader header, TType returnType, int requiredParameterCount, int genericParameterCount, System.Collections.Immutable.ImmutableArray<TType> parameterTypes) { throw null;}
         public int GenericParameterCount { get { throw null; } }
@@ -1864,7 +1864,7 @@ public partial struct MethodSignature<TType>
         public TType ReturnType { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodSpecification
+    public readonly partial struct MethodSpecification
     {
         public System.Reflection.Metadata.EntityHandle Method { get { throw null; } }
         public System.Reflection.Metadata.BlobHandle Signature { get { throw null; } }
@@ -1872,7 +1872,7 @@ public partial struct MethodSpecification
         public System.Reflection.Metadata.CustomAttributeHandleCollection GetCustomAttributes() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodSpecificationHandle : System.IEquatable<System.Reflection.Metadata.MethodSpecificationHandle>
+    public readonly partial struct MethodSpecificationHandle : System.IEquatable<System.Reflection.Metadata.MethodSpecificationHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1886,7 +1886,7 @@ public partial struct MethodSpecificationHandle : System.IEquatable<System.Refle
         public static bool operator !=(System.Reflection.Metadata.MethodSpecificationHandle left, System.Reflection.Metadata.MethodSpecificationHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ModuleDefinition
+    public readonly partial struct ModuleDefinition
     {
         public System.Reflection.Metadata.GuidHandle BaseGenerationId { get { throw null; } }
         public int Generation { get { throw null; } }
@@ -1895,7 +1895,7 @@ public partial struct ModuleDefinition
         public System.Reflection.Metadata.StringHandle Name { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ModuleDefinitionHandle : System.IEquatable<System.Reflection.Metadata.ModuleDefinitionHandle>
+    public readonly partial struct ModuleDefinitionHandle : System.IEquatable<System.Reflection.Metadata.ModuleDefinitionHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1909,13 +1909,13 @@ public partial struct ModuleDefinitionHandle : System.IEquatable<System.Reflecti
         public static bool operator !=(System.Reflection.Metadata.ModuleDefinitionHandle left, System.Reflection.Metadata.ModuleDefinitionHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ModuleReference
+    public readonly partial struct ModuleReference
     {
         public System.Reflection.Metadata.StringHandle Name { get { throw null; } }
         public System.Reflection.Metadata.CustomAttributeHandleCollection GetCustomAttributes() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ModuleReferenceHandle : System.IEquatable<System.Reflection.Metadata.ModuleReferenceHandle>
+    public readonly partial struct ModuleReferenceHandle : System.IEquatable<System.Reflection.Metadata.ModuleReferenceHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1938,7 +1938,7 @@ public partial struct NamespaceDefinition
         public System.Collections.Immutable.ImmutableArray<System.Reflection.Metadata.TypeDefinitionHandle> TypeDefinitions { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct NamespaceDefinitionHandle : System.IEquatable<System.Reflection.Metadata.NamespaceDefinitionHandle>
+    public readonly partial struct NamespaceDefinitionHandle : System.IEquatable<System.Reflection.Metadata.NamespaceDefinitionHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1950,7 +1950,7 @@ public partial struct NamespaceDefinitionHandle : System.IEquatable<System.Refle
         public static bool operator !=(System.Reflection.Metadata.NamespaceDefinitionHandle left, System.Reflection.Metadata.NamespaceDefinitionHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct Parameter
+    public readonly partial struct Parameter
     {
         public System.Reflection.ParameterAttributes Attributes { get { throw null; } }
         public System.Reflection.Metadata.StringHandle Name { get { throw null; } }
@@ -1960,7 +1960,7 @@ public partial struct Parameter
         public System.Reflection.Metadata.BlobHandle GetMarshallingDescriptor() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ParameterHandle : System.IEquatable<System.Reflection.Metadata.ParameterHandle>
+    public readonly partial struct ParameterHandle : System.IEquatable<System.Reflection.Metadata.ParameterHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -1974,7 +1974,7 @@ public partial struct ParameterHandle : System.IEquatable<System.Reflection.Meta
         public static bool operator !=(System.Reflection.Metadata.ParameterHandle left, System.Reflection.Metadata.ParameterHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ParameterHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.ParameterHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.ParameterHandle>, System.Collections.IEnumerable
+    public readonly partial struct ParameterHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.ParameterHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.ParameterHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.ParameterHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -2036,13 +2036,13 @@ public enum PrimitiveTypeCode : byte
         Void = (byte)1,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct PropertyAccessors
+    public readonly partial struct PropertyAccessors
     {
         public System.Reflection.Metadata.MethodDefinitionHandle Getter { get { throw null; } }
         public System.Reflection.Metadata.MethodDefinitionHandle Setter { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct PropertyDefinition
+    public readonly partial struct PropertyDefinition
     {
         public System.Reflection.PropertyAttributes Attributes { get { throw null; } }
         public System.Reflection.Metadata.StringHandle Name { get { throw null; } }
@@ -2053,7 +2053,7 @@ public partial struct PropertyDefinition
         public System.Reflection.Metadata.ConstantHandle GetDefaultValue() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct PropertyDefinitionHandle : System.IEquatable<System.Reflection.Metadata.PropertyDefinitionHandle>
+    public readonly partial struct PropertyDefinitionHandle : System.IEquatable<System.Reflection.Metadata.PropertyDefinitionHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -2067,7 +2067,7 @@ public partial struct PropertyDefinitionHandle : System.IEquatable<System.Reflec
         public static bool operator !=(System.Reflection.Metadata.PropertyDefinitionHandle left, System.Reflection.Metadata.PropertyDefinitionHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct PropertyDefinitionHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.PropertyDefinitionHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.PropertyDefinitionHandle>, System.Collections.IEnumerable
+    public readonly partial struct PropertyDefinitionHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.PropertyDefinitionHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.PropertyDefinitionHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.PropertyDefinitionHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -2084,14 +2084,14 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ReservedBlob<THandle> where THandle : struct
+    public readonly partial struct ReservedBlob<THandle> where THandle : struct
     {
         public System.Reflection.Metadata.Blob Content { get { throw null; } }
         public THandle Handle { get { throw null; } }
         public System.Reflection.Metadata.BlobWriter CreateWriter() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct SequencePoint : System.IEquatable<System.Reflection.Metadata.SequencePoint>
+    public readonly partial struct SequencePoint : System.IEquatable<System.Reflection.Metadata.SequencePoint>
     {
         public const int HiddenLine = 16707566;
         public System.Reflection.Metadata.DocumentHandle Document { get { throw null; } }
@@ -2106,7 +2106,7 @@ public partial struct SequencePoint : System.IEquatable<System.Reflection.Metada
         public override int GetHashCode() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct SequencePointCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.SequencePoint>, System.Collections.IEnumerable
+    public readonly partial struct SequencePointCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.SequencePoint>, System.Collections.IEnumerable
     {
         public System.Reflection.Metadata.SequencePointCollection.Enumerator GetEnumerator() { throw null; }
         System.Collections.Generic.IEnumerator<System.Reflection.Metadata.SequencePoint> System.Collections.Generic.IEnumerable<System.Reflection.Metadata.SequencePoint>.GetEnumerator() { throw null; }
@@ -2229,7 +2229,7 @@ public enum SignatureTypeKind : byte
         ValueType = (byte)17,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct StandaloneSignature
+    public readonly partial struct StandaloneSignature
     {
         public System.Reflection.Metadata.BlobHandle Signature { get { throw null; } }
         public System.Collections.Immutable.ImmutableArray<TType> DecodeLocalSignature<TType, TGenericContext>(System.Reflection.Metadata.ISignatureTypeProvider<TType, TGenericContext> provider, TGenericContext genericContext) { throw null; }
@@ -2238,7 +2238,7 @@ public partial struct StandaloneSignature
         public System.Reflection.Metadata.StandaloneSignatureKind GetKind() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct StandaloneSignatureHandle : System.IEquatable<System.Reflection.Metadata.StandaloneSignatureHandle>
+    public readonly partial struct StandaloneSignatureHandle : System.IEquatable<System.Reflection.Metadata.StandaloneSignatureHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -2257,7 +2257,7 @@ public enum StandaloneSignatureKind
         Method = 0,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct StringHandle : System.IEquatable<System.Reflection.Metadata.StringHandle>
+    public readonly partial struct StringHandle : System.IEquatable<System.Reflection.Metadata.StringHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -2269,7 +2269,7 @@ public partial struct StringHandle : System.IEquatable<System.Reflection.Metadat
         public static bool operator !=(System.Reflection.Metadata.StringHandle left, System.Reflection.Metadata.StringHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct TypeDefinition
+    public readonly partial struct TypeDefinition
     {
         public System.Reflection.TypeAttributes Attributes { get { throw null; } }
         public System.Reflection.Metadata.EntityHandle BaseType { get { throw null; } }
@@ -2290,7 +2290,7 @@ public partial struct TypeDefinition
         public System.Reflection.Metadata.PropertyDefinitionHandleCollection GetProperties() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct TypeDefinitionHandle : System.IEquatable<System.Reflection.Metadata.TypeDefinitionHandle>
+    public readonly partial struct TypeDefinitionHandle : System.IEquatable<System.Reflection.Metadata.TypeDefinitionHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -2304,7 +2304,7 @@ public partial struct TypeDefinitionHandle : System.IEquatable<System.Reflection
         public static bool operator !=(System.Reflection.Metadata.TypeDefinitionHandle left, System.Reflection.Metadata.TypeDefinitionHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct TypeDefinitionHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.TypeDefinitionHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.TypeDefinitionHandle>, System.Collections.IEnumerable
+    public readonly partial struct TypeDefinitionHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.TypeDefinitionHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.TypeDefinitionHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.TypeDefinitionHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -2321,7 +2321,7 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct TypeLayout
+    public readonly partial struct TypeLayout
     {
         public TypeLayout(int size, int packingSize) { throw null;}
         public bool IsDefault { get { throw null; } }
@@ -2329,14 +2329,14 @@ public partial struct TypeLayout
         public int Size { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct TypeReference
+    public readonly partial struct TypeReference
     {
         public System.Reflection.Metadata.StringHandle Name { get { throw null; } }
         public System.Reflection.Metadata.StringHandle Namespace { get { throw null; } }
         public System.Reflection.Metadata.EntityHandle ResolutionScope { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct TypeReferenceHandle : System.IEquatable<System.Reflection.Metadata.TypeReferenceHandle>
+    public readonly partial struct TypeReferenceHandle : System.IEquatable<System.Reflection.Metadata.TypeReferenceHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -2350,7 +2350,7 @@ public partial struct TypeReferenceHandle : System.IEquatable<System.Reflection.
         public static bool operator !=(System.Reflection.Metadata.TypeReferenceHandle left, System.Reflection.Metadata.TypeReferenceHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct TypeReferenceHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.TypeReferenceHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.TypeReferenceHandle>, System.Collections.IEnumerable
+    public readonly partial struct TypeReferenceHandleCollection : System.Collections.Generic.IEnumerable<System.Reflection.Metadata.TypeReferenceHandle>, System.Collections.Generic.IReadOnlyCollection<System.Reflection.Metadata.TypeReferenceHandle>, System.Collections.IEnumerable
     {
         public int Count { get { throw null; } }
         public System.Reflection.Metadata.TypeReferenceHandleCollection.Enumerator GetEnumerator() { throw null; }
@@ -2367,14 +2367,14 @@ void System.IDisposable.Dispose() { }
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct TypeSpecification
+    public readonly partial struct TypeSpecification
     {
         public System.Reflection.Metadata.BlobHandle Signature { get { throw null; } }
         public TType DecodeSignature<TType, TGenericContext>(System.Reflection.Metadata.ISignatureTypeProvider<TType, TGenericContext> provider, TGenericContext genericContext) { throw null; }
         public System.Reflection.Metadata.CustomAttributeHandleCollection GetCustomAttributes() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct TypeSpecificationHandle : System.IEquatable<System.Reflection.Metadata.TypeSpecificationHandle>
+    public readonly partial struct TypeSpecificationHandle : System.IEquatable<System.Reflection.Metadata.TypeSpecificationHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -2388,7 +2388,7 @@ public partial struct TypeSpecificationHandle : System.IEquatable<System.Reflect
         public static bool operator !=(System.Reflection.Metadata.TypeSpecificationHandle left, System.Reflection.Metadata.TypeSpecificationHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct UserStringHandle : System.IEquatable<System.Reflection.Metadata.UserStringHandle>
+    public readonly partial struct UserStringHandle : System.IEquatable<System.Reflection.Metadata.UserStringHandle>
     {
         public bool IsNil { get { throw null; } }
         public override bool Equals(object obj) { throw null; }
@@ -2403,14 +2403,14 @@ public partial struct UserStringHandle : System.IEquatable<System.Reflection.Met
 namespace System.Reflection.Metadata.Ecma335
 {
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ArrayShapeEncoder
+    public readonly partial struct ArrayShapeEncoder
     {
         public ArrayShapeEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
         public void Shape(int rank, System.Collections.Immutable.ImmutableArray<int> sizes, System.Collections.Immutable.ImmutableArray<int> lowerBounds) { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct BlobEncoder
+    public readonly partial struct BlobEncoder
     {
         public BlobEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2452,7 +2452,7 @@ public void AddFilterRegion(System.Reflection.Metadata.Ecma335.LabelHandle trySt
         public void AddFinallyRegion(System.Reflection.Metadata.Ecma335.LabelHandle tryStart, System.Reflection.Metadata.Ecma335.LabelHandle tryEnd, System.Reflection.Metadata.Ecma335.LabelHandle handlerStart, System.Reflection.Metadata.Ecma335.LabelHandle handlerEnd) { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CustomAttributeArrayTypeEncoder
+    public readonly partial struct CustomAttributeArrayTypeEncoder
     {
         public CustomAttributeArrayTypeEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2460,7 +2460,7 @@ public partial struct CustomAttributeArrayTypeEncoder
         public void ObjectArray() { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CustomAttributeElementTypeEncoder
+    public readonly partial struct CustomAttributeElementTypeEncoder
     {
         public CustomAttributeElementTypeEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2482,21 +2482,21 @@ public void UInt32() { }
         public void UInt64() { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CustomAttributeNamedArgumentsEncoder
+    public readonly partial struct CustomAttributeNamedArgumentsEncoder
     {
         public CustomAttributeNamedArgumentsEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
         public System.Reflection.Metadata.Ecma335.NamedArgumentsEncoder Count(int count) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CustomModifiersEncoder
+    public readonly partial struct CustomModifiersEncoder
     {
         public CustomModifiersEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
         public System.Reflection.Metadata.Ecma335.CustomModifiersEncoder AddModifier(System.Reflection.Metadata.EntityHandle type, bool isOptional) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct EditAndContinueLogEntry : System.IEquatable<System.Reflection.Metadata.Ecma335.EditAndContinueLogEntry>
+    public readonly partial struct EditAndContinueLogEntry : System.IEquatable<System.Reflection.Metadata.Ecma335.EditAndContinueLogEntry>
     {
         public EditAndContinueLogEntry(System.Reflection.Metadata.EntityHandle handle, System.Reflection.Metadata.Ecma335.EditAndContinueOperation operation) { throw null;}
         public System.Reflection.Metadata.EntityHandle Handle { get { throw null; } }
@@ -2515,7 +2515,7 @@ public enum EditAndContinueOperation
         Default = 0,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ExceptionRegionEncoder
+    public readonly partial struct ExceptionRegionEncoder
     {
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
         public bool HasSmallFormat { get { throw null; } }
@@ -2532,7 +2532,7 @@ public static partial class ExportedTypeExtensions
         public static int GetTypeDefinitionId(this System.Reflection.Metadata.ExportedType exportedType) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct FixedArgumentsEncoder
+    public readonly partial struct FixedArgumentsEncoder
     {
         public FixedArgumentsEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2545,7 +2545,7 @@ public enum FunctionPointerAttributes
         None = 0,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct GenericTypeArgumentsEncoder
+    public readonly partial struct GenericTypeArgumentsEncoder
     {
         public GenericTypeArgumentsEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2559,7 +2559,7 @@ public enum HeapIndex
         UserString = 0,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct InstructionEncoder
+    public readonly partial struct InstructionEncoder
     {
         public InstructionEncoder(System.Reflection.Metadata.BlobBuilder codeBuilder, System.Reflection.Metadata.Ecma335.ControlFlowBuilder controlFlowBuilder=null) { throw null;}
         public System.Reflection.Metadata.BlobBuilder CodeBuilder { get { throw null; } }
@@ -2589,7 +2589,7 @@ public void Token(int token) { }
         public void Token(System.Reflection.Metadata.EntityHandle handle) { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct LabelHandle : System.IEquatable<System.Reflection.Metadata.Ecma335.LabelHandle>
+    public readonly partial struct LabelHandle : System.IEquatable<System.Reflection.Metadata.Ecma335.LabelHandle>
     {
         public int Id { get { throw null; } }
         public bool IsNil { get { throw null; } }
@@ -2600,7 +2600,7 @@ public partial struct LabelHandle : System.IEquatable<System.Reflection.Metadata
         public static bool operator !=(System.Reflection.Metadata.Ecma335.LabelHandle left, System.Reflection.Metadata.Ecma335.LabelHandle right) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct LiteralEncoder
+    public readonly partial struct LiteralEncoder
     {
         public LiteralEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2612,21 +2612,21 @@ public void TaggedVector(System.Action<System.Reflection.Metadata.Ecma335.Custom
         public System.Reflection.Metadata.Ecma335.VectorEncoder Vector() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct LiteralsEncoder
+    public readonly partial struct LiteralsEncoder
     {
         public LiteralsEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
         public System.Reflection.Metadata.Ecma335.LiteralEncoder AddLiteral() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct LocalVariablesEncoder
+    public readonly partial struct LocalVariablesEncoder
     {
         public LocalVariablesEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
         public System.Reflection.Metadata.Ecma335.LocalVariableTypeEncoder AddVariable() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct LocalVariableTypeEncoder
+    public readonly partial struct LocalVariableTypeEncoder
     {
         public LocalVariableTypeEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2801,14 +2801,14 @@ public enum MethodBodyAttributes
         None = 0,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodBodyStreamEncoder
+    public readonly partial struct MethodBodyStreamEncoder
     {
         public MethodBodyStreamEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
         public System.Reflection.Metadata.Ecma335.MethodBodyStreamEncoder.MethodBody AddMethodBody(int codeSize, int maxStack=8, int exceptionRegionCount=0, bool hasSmallExceptionRegions=true, System.Reflection.Metadata.StandaloneSignatureHandle localVariablesSignature=default(System.Reflection.Metadata.StandaloneSignatureHandle), System.Reflection.Metadata.Ecma335.MethodBodyAttributes attributes=(System.Reflection.Metadata.Ecma335.MethodBodyAttributes)(1)) { throw null; }
         public int AddMethodBody(System.Reflection.Metadata.Ecma335.InstructionEncoder instructionEncoder, int maxStack=8, System.Reflection.Metadata.StandaloneSignatureHandle localVariablesSignature=default(System.Reflection.Metadata.StandaloneSignatureHandle), System.Reflection.Metadata.Ecma335.MethodBodyAttributes attributes=(System.Reflection.Metadata.Ecma335.MethodBodyAttributes)(1)) { throw null; }
         [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-        public partial struct MethodBody
+        public readonly partial struct MethodBody
         {
             public System.Reflection.Metadata.Ecma335.ExceptionRegionEncoder ExceptionRegions { get { throw null; } }
             public System.Reflection.Metadata.Blob Instructions { get { throw null; } }
@@ -2816,7 +2816,7 @@ public partial struct MethodBody
         }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct MethodSignatureEncoder
+    public readonly partial struct MethodSignatureEncoder
     {
         public MethodSignatureEncoder(System.Reflection.Metadata.BlobBuilder builder, bool hasVarArgs) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2825,7 +2825,7 @@ public void Parameters(int parameterCount, System.Action<System.Reflection.Metad
         public void Parameters(int parameterCount, out System.Reflection.Metadata.Ecma335.ReturnTypeEncoder returnType, out System.Reflection.Metadata.Ecma335.ParametersEncoder parameters) { returnType = default(System.Reflection.Metadata.Ecma335.ReturnTypeEncoder); parameters = default(System.Reflection.Metadata.Ecma335.ParametersEncoder); }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct NamedArgumentsEncoder
+    public readonly partial struct NamedArgumentsEncoder
     {
         public NamedArgumentsEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2833,7 +2833,7 @@ public void AddArgument(bool isField, System.Action<System.Reflection.Metadata.E
         public void AddArgument(bool isField, out System.Reflection.Metadata.Ecma335.NamedArgumentTypeEncoder type, out System.Reflection.Metadata.Ecma335.NameEncoder name, out System.Reflection.Metadata.Ecma335.LiteralEncoder literal) { type = default(System.Reflection.Metadata.Ecma335.NamedArgumentTypeEncoder); name = default(System.Reflection.Metadata.Ecma335.NameEncoder); literal = default(System.Reflection.Metadata.Ecma335.LiteralEncoder); }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct NamedArgumentTypeEncoder
+    public readonly partial struct NamedArgumentTypeEncoder
     {
         public NamedArgumentTypeEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2842,14 +2842,14 @@ public void Object() { }
         public System.Reflection.Metadata.Ecma335.CustomAttributeArrayTypeEncoder SZArray() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct NameEncoder
+    public readonly partial struct NameEncoder
     {
         public NameEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
         public void Name(string name) { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ParametersEncoder
+    public readonly partial struct ParametersEncoder
     {
         public ParametersEncoder(System.Reflection.Metadata.BlobBuilder builder, bool hasVarArgs=false) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2858,7 +2858,7 @@ public partial struct ParametersEncoder
         public System.Reflection.Metadata.Ecma335.ParametersEncoder StartVarArgs() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ParameterTypeEncoder
+    public readonly partial struct ParameterTypeEncoder
     {
         public ParameterTypeEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2867,7 +2867,7 @@ public partial struct ParameterTypeEncoder
         public void TypedReference() { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct PermissionSetEncoder
+    public readonly partial struct PermissionSetEncoder
     {
         public PermissionSetEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2883,7 +2883,7 @@ public PortablePdbBuilder(System.Reflection.Metadata.Ecma335.MetadataBuilder tab
         public System.Reflection.Metadata.BlobContentId Serialize(System.Reflection.Metadata.BlobBuilder builder) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ReturnTypeEncoder
+    public readonly partial struct ReturnTypeEncoder
     {
         public ReturnTypeEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2893,7 +2893,7 @@ public void TypedReference() { }
         public void Void() { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ScalarEncoder
+    public readonly partial struct ScalarEncoder
     {
         public ScalarEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -2902,7 +2902,7 @@ public void NullArray() { }
         public void SystemType(string serializedTypeName) { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct SignatureDecoder<TType, TGenericContext>
+    public readonly partial struct SignatureDecoder<TType, TGenericContext>
     {
         public SignatureDecoder(System.Reflection.Metadata.ISignatureTypeProvider<TType, TGenericContext> provider, System.Reflection.Metadata.MetadataReader metadataReader, TGenericContext genericContext) { throw null;}
         public TType DecodeFieldSignature(ref System.Reflection.Metadata.BlobReader blobReader) { throw null; }
@@ -2912,7 +2912,7 @@ public partial struct SignatureDecoder<TType, TGenericContext>
         public TType DecodeType(ref System.Reflection.Metadata.BlobReader blobReader, bool allowTypeSpecifications=false) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct SignatureTypeEncoder
+    public readonly partial struct SignatureTypeEncoder
     {
         public SignatureTypeEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -3002,7 +3002,7 @@ public enum TableIndex : byte
         TypeSpec = (byte)27,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct VectorEncoder
+    public readonly partial struct VectorEncoder
     {
         public VectorEncoder(System.Reflection.Metadata.BlobBuilder builder) { throw null;}
         public System.Reflection.Metadata.BlobBuilder Builder { get { throw null; } }
@@ -3030,7 +3030,7 @@ public enum Characteristics : ushort
         UpSystemOnly = (ushort)16384,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct CodeViewDebugDirectoryData
+    public readonly partial struct CodeViewDebugDirectoryData
     {
         public int Age { get { throw null; } }
         public System.Guid Guid { get { throw null; } }
@@ -3081,7 +3081,7 @@ public void AddEmbeddedPortablePdbEntry(System.Reflection.Metadata.BlobBuilder d
         public void AddReproducibleEntry() { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct DebugDirectoryEntry
+    public readonly partial struct DebugDirectoryEntry
     {
         public DebugDirectoryEntry(uint stamp, ushort majorVersion, ushort minorVersion, System.Reflection.PortableExecutable.DebugDirectoryEntryType type, int dataSize, int dataRelativeVirtualAddress, int dataPointer) { throw null;}
         public int DataPointer { get { throw null; } }
@@ -3102,7 +3102,7 @@ public enum DebugDirectoryEntryType
         Unknown = 0,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct DirectoryEntry
+    public readonly partial struct DirectoryEntry
     {
         public readonly int RelativeVirtualAddress;
         public readonly int Size;
@@ -3299,7 +3299,7 @@ public enum PEMagic : ushort
         PE32Plus = (ushort)523,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct PEMemoryBlock
+    public readonly partial struct PEMemoryBlock
     {
         public int Length { get { throw null; } }
         public unsafe byte* Pointer { get { throw null; } }
@@ -3395,7 +3395,7 @@ public enum SectionCharacteristics : uint
         TypeReg = (uint)0,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct SectionHeader
+    public readonly partial struct SectionHeader
     {
         public string Name { get { throw null; } }
         public ushort NumberOfLineNumbers { get { throw null; } }
@@ -3409,7 +3409,7 @@ public partial struct SectionHeader
         public int VirtualSize { get { throw null; } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct SectionLocation
+    public readonly partial struct SectionLocation
     {
         public SectionLocation(int relativeVirtualAddress, int pointerToRawData) { throw null;}
         public int PointerToRawData { get { throw null; } }
diff --git a/src/libraries/System.Runtime.InteropServices.RuntimeInformation/ref/System.Runtime.InteropServices.RuntimeInformation.cs b/src/libraries/System.Runtime.InteropServices.RuntimeInformation/ref/System.Runtime.InteropServices.RuntimeInformation.cs
index f18b400588075..7b89908c6d22d 100644
--- a/src/libraries/System.Runtime.InteropServices.RuntimeInformation/ref/System.Runtime.InteropServices.RuntimeInformation.cs
+++ b/src/libraries/System.Runtime.InteropServices.RuntimeInformation/ref/System.Runtime.InteropServices.RuntimeInformation.cs
@@ -9,7 +9,7 @@
 namespace System.Runtime.InteropServices
 {
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct OSPlatform : System.IEquatable<System.Runtime.InteropServices.OSPlatform>
+    public readonly partial struct OSPlatform : System.IEquatable<System.Runtime.InteropServices.OSPlatform>
     {
         public static System.Runtime.InteropServices.OSPlatform Linux { get { throw null; } }
         public static System.Runtime.InteropServices.OSPlatform OSX { get { throw null; } }
diff --git a/src/libraries/System.Runtime.Numerics/ref/System.Runtime.Numerics.cs b/src/libraries/System.Runtime.Numerics/ref/System.Runtime.Numerics.cs
index d1e87b9a0a14b..1b158eb363523 100644
--- a/src/libraries/System.Runtime.Numerics/ref/System.Runtime.Numerics.cs
+++ b/src/libraries/System.Runtime.Numerics/ref/System.Runtime.Numerics.cs
@@ -9,7 +9,7 @@
 namespace System.Numerics
 {
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct BigInteger : System.IComparable, System.IComparable<System.Numerics.BigInteger>, System.IEquatable<System.Numerics.BigInteger>, System.IFormattable
+    public readonly partial struct BigInteger : System.IComparable, System.IComparable<System.Numerics.BigInteger>, System.IEquatable<System.Numerics.BigInteger>, System.IFormattable
     {
         [System.CLSCompliantAttribute(false)]
         public BigInteger(byte[] value) { throw null; }
diff --git a/src/libraries/System.Runtime/ref/System.Runtime.cs b/src/libraries/System.Runtime/ref/System.Runtime.cs
index 82ffee5373de1..4d0ef09b684d1 100644
--- a/src/libraries/System.Runtime/ref/System.Runtime.cs
+++ b/src/libraries/System.Runtime/ref/System.Runtime.cs
@@ -639,7 +639,7 @@ public CLSCompliantAttribute(bool isCompliant) { }
     }
     public delegate int Comparison<in T>(T x, T y);
     public delegate TOutput Converter<in TInput, out TOutput>(TInput input);
-    public partial struct DateTime : System.IComparable, System.IComparable<System.DateTime>, System.IConvertible, System.IEquatable<System.DateTime>, System.IFormattable, System.Runtime.Serialization.ISerializable
+    public readonly partial struct DateTime : System.IComparable, System.IComparable<System.DateTime>, System.IConvertible, System.IEquatable<System.DateTime>, System.IFormattable, System.Runtime.Serialization.ISerializable
     {
         public static readonly System.DateTime MaxValue;
         public static readonly System.DateTime MinValue;
@@ -4054,7 +4054,7 @@ public static class KeyValuePair
         public static KeyValuePair<TKey, TValue> Create<TKey, TValue>(TKey key, TValue value) { throw null; }        
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct KeyValuePair<TKey, TValue>
+    public readonly partial struct KeyValuePair<TKey, TValue>
     {
         public KeyValuePair(TKey key, TValue value) { throw null; }
         [System.ComponentModel.EditorBrowsable(System.ComponentModel.EditorBrowsableState.Never)]
@@ -6165,7 +6165,7 @@ protected ParameterInfo() { }
         public override string ToString() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public struct ParameterModifier
+    public readonly struct ParameterModifier
     {
         public ParameterModifier(int parameterCount) { }
         public bool this[int index] { get { throw null; } set { } }
@@ -6564,10 +6564,10 @@ public void Clear() { }
         public bool TryGetValue(TKey key, out TValue value) { throw null; }
         public delegate TValue CreateValueCallback(TKey key);
     }
-    public partial struct ConfiguredValueTaskAwaitable<TResult>
+    public readonly partial struct ConfiguredValueTaskAwaitable<TResult>
     {
         public System.Runtime.CompilerServices.ConfiguredValueTaskAwaitable<TResult>.ConfiguredValueTaskAwaiter GetAwaiter() { throw null; }
-        public partial struct ConfiguredValueTaskAwaiter : System.Runtime.CompilerServices.ICriticalNotifyCompletion, System.Runtime.CompilerServices.INotifyCompletion
+        public readonly partial struct ConfiguredValueTaskAwaiter : System.Runtime.CompilerServices.ICriticalNotifyCompletion, System.Runtime.CompilerServices.INotifyCompletion
         {
             public bool IsCompleted { get { throw null; } }
             public TResult GetResult() { throw null; }
@@ -6751,7 +6751,7 @@ public sealed partial class UnsafeValueTypeAttribute : System.Attribute
         public UnsafeValueTypeAttribute() { }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct ValueTaskAwaiter<TResult> : System.Runtime.CompilerServices.ICriticalNotifyCompletion, System.Runtime.CompilerServices.INotifyCompletion
+    public readonly partial struct ValueTaskAwaiter<TResult> : System.Runtime.CompilerServices.ICriticalNotifyCompletion, System.Runtime.CompilerServices.INotifyCompletion
     {
         public bool IsCompleted { get { throw null; } }
         public TResult GetResult() { throw null; }
@@ -7060,7 +7060,7 @@ private SerializationInfoEnumerator() { }
         public void Reset() { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct StreamingContext
+    public readonly partial struct StreamingContext
     {
         public StreamingContext(System.Runtime.Serialization.StreamingContextStates state) { }
         public StreamingContext(System.Runtime.Serialization.StreamingContextStates state, object additional) { }
@@ -7997,7 +7997,7 @@ public UnobservedTaskExceptionEventArgs(System.AggregateException exception) { }
         public void SetObserved() { }
     }
     [System.Runtime.CompilerServices.AsyncMethodBuilderAttribute(typeof(System.Runtime.CompilerServices.AsyncValueTaskMethodBuilder<>))]
-    public partial struct ValueTask<TResult> : System.IEquatable<System.Threading.Tasks.ValueTask<TResult>>
+    public readonly partial struct ValueTask<TResult> : System.IEquatable<System.Threading.Tasks.ValueTask<TResult>>
     {
         public ValueTask(System.Threading.Tasks.Task<TResult> task) { throw null; }
         public ValueTask(TResult result) { throw null; }
diff --git a/src/libraries/System.Security.Cryptography.Primitives/ref/System.Security.Cryptography.Primitives.cs b/src/libraries/System.Security.Cryptography.Primitives/ref/System.Security.Cryptography.Primitives.cs
index a0df0ea2fdbf0..ec17f1d1bb57c 100644
--- a/src/libraries/System.Security.Cryptography.Primitives/ref/System.Security.Cryptography.Primitives.cs
+++ b/src/libraries/System.Security.Cryptography.Primitives/ref/System.Security.Cryptography.Primitives.cs
@@ -103,7 +103,7 @@ protected virtual void Dispose(bool disposing) { }
         protected virtual bool TryHashFinal(Span<byte> destination, out int bytesWritten) { throw null; }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct HashAlgorithmName : System.IEquatable<System.Security.Cryptography.HashAlgorithmName>
+    public readonly partial struct HashAlgorithmName : System.IEquatable<System.Security.Cryptography.HashAlgorithmName>
     {
         public HashAlgorithmName(string name) { throw null; }
         public static System.Security.Cryptography.HashAlgorithmName MD5 { get { throw null; } }
diff --git a/src/libraries/System.ServiceProcess.ServiceController/ref/System.ServiceProcess.ServiceController.cs b/src/libraries/System.ServiceProcess.ServiceController/ref/System.ServiceProcess.ServiceController.cs
index e10f43db51b6d..0e3c0ebac8154 100644
--- a/src/libraries/System.ServiceProcess.ServiceController/ref/System.ServiceProcess.ServiceController.cs
+++ b/src/libraries/System.ServiceProcess.ServiceController/ref/System.ServiceProcess.ServiceController.cs
@@ -116,7 +116,7 @@ public enum ServiceType
         Win32ShareProcess = 32,
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct SessionChangeDescription
+    public readonly partial struct SessionChangeDescription
     {
         public System.ServiceProcess.SessionChangeReason Reason { get { throw null; } }
         public int SessionId { get { throw null; } }
diff --git a/src/libraries/System.Threading.Tasks.Dataflow/ref/System.Threading.Tasks.Dataflow.cs b/src/libraries/System.Threading.Tasks.Dataflow/ref/System.Threading.Tasks.Dataflow.cs
index 9e4e020e1e8d7..2d841d5505ef6 100644
--- a/src/libraries/System.Threading.Tasks.Dataflow/ref/System.Threading.Tasks.Dataflow.cs
+++ b/src/libraries/System.Threading.Tasks.Dataflow/ref/System.Threading.Tasks.Dataflow.cs
@@ -159,7 +159,7 @@ public DataflowLinkOptions() { }
         public bool PropagateCompletion { get { throw null; } set { } }
     }
     [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
-    public partial struct DataflowMessageHeader : System.IEquatable<System.Threading.Tasks.Dataflow.DataflowMessageHeader>
+    public readonly partial struct DataflowMessageHeader : System.IEquatable<System.Threading.Tasks.Dataflow.DataflowMessageHeader>
     {
         public DataflowMessageHeader(long id) { throw null;}
         public long Id { get { throw null; } }