Merge branch 'master' into update_from_master

26 files changed, 647 insertions, 11 deletions

diff --git a/src/mscorlib/shared/System/Runtime/CompilerServices/AsyncMethodBuilderAttribute.cs b/src/mscorlib/shared/System/Runtime/CompilerServices/AsyncMethodBuilderAttribute.cs
new file mode 100644
index 0000000000..688a3a01ba
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/CompilerServices/AsyncMethodBuilderAttribute.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Indicates the type of the async method builder that should be used by a language compiler to
+    /// build the attributed type when used as the return type of an async method.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Interface | AttributeTargets.Delegate | AttributeTargets.Enum, Inherited = false, AllowMultiple = false)]
+    public sealed class AsyncMethodBuilderAttribute : Attribute
+    {
+        /// <summary>Initializes the <see cref="AsyncMethodBuilderAttribute"/>.</summary>
+        /// <param name="builderType">The <see cref="Type"/> of the associated builder.</param>
+        public AsyncMethodBuilderAttribute(Type builderType) => BuilderType = builderType;
+
+        /// <summary>Gets the <see cref="Type"/> of the associated builder.</summary>
+        public Type BuilderType { get; }
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/CompilerServices/AsyncValueTaskMethodBuilder.cs b/src/mscorlib/shared/System/Runtime/CompilerServices/AsyncValueTaskMethodBuilder.cs
new file mode 100644
index 0000000000..813d9e5cd7
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/CompilerServices/AsyncValueTaskMethodBuilder.cs
@@ -0,0 +1,111 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using System.Security;
+using System.Threading.Tasks;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>Represents a builder for asynchronous methods that returns a <see cref="ValueTask{TResult}"/>.</summary>
+    /// <typeparam name="TResult">The type of the result.</typeparam>
+    [StructLayout(LayoutKind.Auto)]
+    public struct AsyncValueTaskMethodBuilder<TResult>
+    {
+        /// <summary>The <see cref="AsyncTaskMethodBuilder{TResult}"/> to which most operations are delegated.</summary>
+        private AsyncTaskMethodBuilder<TResult> _methodBuilder; // mutable struct; do not make it readonly
+        /// <summary>The result for this builder, if it's completed before any awaits occur.</summary>
+        private TResult _result;
+        /// <summary>true if <see cref="_result"/> contains the synchronous result for the async method; otherwise, false.</summary>
+        private bool _haveResult;
+        /// <summary>true if the builder should be used for setting/getting the result; otherwise, false.</summary>
+        private bool _useBuilder;
+
+        /// <summary>Creates an instance of the <see cref="AsyncValueTaskMethodBuilder{TResult}"/> struct.</summary>
+        /// <returns>The initialized instance.</returns>
+        public static AsyncValueTaskMethodBuilder<TResult> Create() =>
+#if CORECLR
+            // _methodBuilder should be initialized to AsyncTaskMethodBuilder<TResult>.Create(), but on coreclr
+            // that Create() is a nop, so we can just return the default here.
+            default(AsyncValueTaskMethodBuilder<TResult>);
+#else
+            // corert's AsyncTaskMethodBuilder<TResult>.Create() currently does additional debugger-related
+            // work, so we need to delegate to it.
+            new AsyncValueTaskMethodBuilder<TResult>() { _methodBuilder = AsyncTaskMethodBuilder<TResult>.Create() };
+#endif
+
+        /// <summary>Begins running the builder with the associated state machine.</summary>
+        /// <typeparam name="TStateMachine">The type of the state machine.</typeparam>
+        /// <param name="stateMachine">The state machine instance, passed by reference.</param>
+        public void Start<TStateMachine>(ref TStateMachine stateMachine) where TStateMachine : IAsyncStateMachine =>
+            _methodBuilder.Start(ref stateMachine); // will provide the right ExecutionContext semantics
+
+        /// <summary>Associates the builder with the specified state machine.</summary>
+        /// <param name="stateMachine">The state machine instance to associate with the builder.</param>
+        public void SetStateMachine(IAsyncStateMachine stateMachine) => _methodBuilder.SetStateMachine(stateMachine);
+
+        /// <summary>Marks the task as successfully completed.</summary>
+        /// <param name="result">The result to use to complete the task.</param>
+        public void SetResult(TResult result)
+        {
+            if (_useBuilder)
+            {
+                _methodBuilder.SetResult(result);
+            }
+            else
+            {
+                _result = result;
+                _haveResult = true;
+            }
+        }
+
+        /// <summary>Marks the task as failed and binds the specified exception to the task.</summary>
+        /// <param name="exception">The exception to bind to the task.</param>
+        public void SetException(Exception exception) => _methodBuilder.SetException(exception);
+
+        /// <summary>Gets the task for this builder.</summary>
+        public ValueTask<TResult> Task
+        {
+            get
+            {
+                if (_haveResult)
+                {
+                    return new ValueTask<TResult>(_result);
+                }
+                else
+                {
+                    _useBuilder = true;
+                    return new ValueTask<TResult>(_methodBuilder.Task);
+                }
+            }
+        }
+
+        /// <summary>Schedules the state machine to proceed to the next action when the specified awaiter completes.</summary>
+        /// <typeparam name="TAwaiter">The type of the awaiter.</typeparam>
+        /// <typeparam name="TStateMachine">The type of the state machine.</typeparam>
+        /// <param name="awaiter">the awaiter</param>
+        /// <param name="stateMachine">The state machine.</param>
+        public void AwaitOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)
+            where TAwaiter : INotifyCompletion
+            where TStateMachine : IAsyncStateMachine
+        {
+            _useBuilder = true;
+            _methodBuilder.AwaitOnCompleted(ref awaiter, ref stateMachine);
+        }
+
+        /// <summary>Schedules the state machine to proceed to the next action when the specified awaiter completes.</summary>
+        /// <typeparam name="TAwaiter">The type of the awaiter.</typeparam>
+        /// <typeparam name="TStateMachine">The type of the state machine.</typeparam>
+        /// <param name="awaiter">the awaiter</param>
+        /// <param name="stateMachine">The state machine.</param>
+        [SecuritySafeCritical]
+        public void AwaitUnsafeOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)
+            where TAwaiter : ICriticalNotifyCompletion 
+            where TStateMachine : IAsyncStateMachine
+        {
+            _useBuilder = true;
+            _methodBuilder.AwaitUnsafeOnCompleted(ref awaiter, ref stateMachine);
+        }
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/CompilerServices/ConfiguredValueTaskAwaitable.cs b/src/mscorlib/shared/System/Runtime/CompilerServices/ConfiguredValueTaskAwaitable.cs
new file mode 100644
index 0000000000..4ec931c4af
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/CompilerServices/ConfiguredValueTaskAwaitable.cs
@@ -0,0 +1,71 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>Provides an awaitable type that enables configured awaits on a <see cref="ValueTask{TResult}"/>.</summary>
+    /// <typeparam name="TResult">The type of the result produced.</typeparam>
+    [StructLayout(LayoutKind.Auto)]
+    public struct ConfiguredValueTaskAwaitable<TResult>
+    {
+        /// <summary>The wrapped <see cref="ValueTask{TResult}"/>.</summary>
+        private readonly ValueTask<TResult> _value;
+        /// <summary>true to attempt to marshal the continuation back to the original context captured; otherwise, false.</summary>
+        private readonly bool _continueOnCapturedContext;
+
+        /// <summary>Initializes the awaitable.</summary>
+        /// <param name="value">The wrapped <see cref="ValueTask{TResult}"/>.</param>
+        /// <param name="continueOnCapturedContext">
+        /// true to attempt to marshal the continuation back to the original synchronization context captured; otherwise, false.
+        /// </param>
+        internal ConfiguredValueTaskAwaitable(ValueTask<TResult> value, bool continueOnCapturedContext)
+        {
+            _value = value;
+            _continueOnCapturedContext = continueOnCapturedContext;
+        }
+
+        /// <summary>Returns an awaiter for this <see cref="ConfiguredValueTaskAwaitable{TResult}"/> instance.</summary>
+        public ConfiguredValueTaskAwaiter GetAwaiter() =>
+            new ConfiguredValueTaskAwaiter(_value, _continueOnCapturedContext);
+
+        /// <summary>Provides an awaiter for a <see cref="ConfiguredValueTaskAwaitable{TResult}"/>.</summary>
+        [StructLayout(LayoutKind.Auto)]
+        public struct ConfiguredValueTaskAwaiter : ICriticalNotifyCompletion
+        {
+            /// <summary>The value being awaited.</summary>
+            private ValueTask<TResult> _value; // Methods are called on this; avoid making it readonly so as to avoid unnecessary copies
+            /// <summary>The value to pass to ConfigureAwait.</summary>
+            private readonly bool _continueOnCapturedContext;
+
+            /// <summary>Initializes the awaiter.</summary>
+            /// <param name="value">The value to be awaited.</param>
+            /// <param name="continueOnCapturedContext">The value to pass to ConfigureAwait.</param>
+            internal ConfiguredValueTaskAwaiter(ValueTask<TResult> value, bool continueOnCapturedContext)
+            {
+                _value = value;
+                _continueOnCapturedContext = continueOnCapturedContext;
+            }
+
+            /// <summary>Gets whether the <see cref="ConfiguredValueTaskAwaitable{TResult}"/> has completed.</summary>
+            public bool IsCompleted => _value.IsCompleted;
+
+            /// <summary>Gets the result of the ValueTask.</summary>
+            public TResult GetResult() =>
+                _value._task == null ? 
+                    _value._result : 
+                    _value._task.GetAwaiter().GetResult();
+
+            /// <summary>Schedules the continuation action for the <see cref="ConfiguredValueTaskAwaitable{TResult}"/>.</summary>
+            public void OnCompleted(Action continuation) =>
+                _value.AsTask().ConfigureAwait(_continueOnCapturedContext).GetAwaiter().OnCompleted(continuation);
+
+            /// <summary>Schedules the continuation action for the <see cref="ConfiguredValueTaskAwaitable{TResult}"/>.</summary>
+            public void UnsafeOnCompleted(Action continuation) =>
+                _value.AsTask().ConfigureAwait(_continueOnCapturedContext).GetAwaiter().UnsafeOnCompleted(continuation);
+        }
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/CompilerServices/CustomConstantAttribute.cs b/src/mscorlib/shared/System/Runtime/CompilerServices/CustomConstantAttribute.cs
new file mode 100644
index 0000000000..f75693eb40
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/CompilerServices/CustomConstantAttribute.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter, Inherited = false)]
+    public abstract class CustomConstantAttribute : Attribute
+    {
+        public abstract Object Value { get; }
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/CompilerServices/DateTimeConstantAttribute.cs b/src/mscorlib/shared/System/Runtime/CompilerServices/DateTimeConstantAttribute.cs
new file mode 100644
index 0000000000..813e6803bf
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/CompilerServices/DateTimeConstantAttribute.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter, Inherited = false)]
+    public sealed class DateTimeConstantAttribute : CustomConstantAttribute
+    {
+        private DateTime _date;
+
+        public DateTimeConstantAttribute(long ticks)
+        {
+            _date = new DateTime(ticks);
+        }
+
+        public override Object Value => _date;
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/CompilerServices/DecimalConstantAttribute.cs b/src/mscorlib/shared/System/Runtime/CompilerServices/DecimalConstantAttribute.cs
new file mode 100644
index 0000000000..19db84eb43
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/CompilerServices/DecimalConstantAttribute.cs
@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// Note: If you add a new ctor overloads you need to update ParameterInfo.RawDefaultValue
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter, Inherited = false)]
+    public sealed class DecimalConstantAttribute : Attribute
+    {
+        private Decimal _dec;
+
+        [CLSCompliant(false)]
+        public DecimalConstantAttribute(
+            byte scale,
+            byte sign,
+            uint hi,
+            uint mid,
+            uint low
+        )
+        {
+            _dec = new Decimal((int)low, (int)mid, (int)hi, (sign != 0), scale);
+        }
+
+        public DecimalConstantAttribute(
+            byte scale,
+            byte sign,
+            int hi,
+            int mid,
+            int low
+        )
+        {
+            _dec = new Decimal(low, mid, hi, (sign != 0), scale);
+        }
+
+        public Decimal Value => _dec;
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/CompilerServices/IntrinsicAttribute.cs b/src/mscorlib/shared/System/Runtime/CompilerServices/IntrinsicAttribute.cs
new file mode 100644
index 0000000000..dd01bacc49
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/CompilerServices/IntrinsicAttribute.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    // Calls to methods or references to fields marked with this attribute may be replaced at
+    // some call sites with jit intrinsic expansions.
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Field, Inherited = false)]
+    internal sealed class IntrinsicAttribute : Attribute
+    {
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/CompilerServices/MethodImplAttribute.cs b/src/mscorlib/shared/System/Runtime/CompilerServices/MethodImplAttribute.cs
new file mode 100644
index 0000000000..8e8f93c268
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/CompilerServices/MethodImplAttribute.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    // Custom attribute to specify additional method properties.
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor, Inherited = false)]
+    sealed public class MethodImplAttribute : Attribute
+    {
+        public MethodCodeType MethodCodeType;
+
+        public MethodImplAttribute(MethodImplOptions methodImplOptions)
+        {
+            Value = methodImplOptions;
+        }
+
+        public MethodImplAttribute(short value)
+        {
+            Value = (MethodImplOptions)value;
+        }
+
+        public MethodImplAttribute()
+        {
+        }
+
+        public MethodImplOptions Value { get; }
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/CompilerServices/RuntimeWrappedException.cs b/src/mscorlib/shared/System/Runtime/CompilerServices/RuntimeWrappedException.cs
new file mode 100644
index 0000000000..e4af9be678
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/CompilerServices/RuntimeWrappedException.cs
@@ -0,0 +1,33 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Exception used to wrap all non-CLS compliant exceptions.
+    /// </summary>
+    public sealed class RuntimeWrappedException : Exception
+    {
+        private Object _wrappedException; // EE expects this name
+
+        // Not an api but has to be public as System.Linq.Expression invokes this through Reflection when an expression
+        // throws an object that doesn't derive from Exception.
+        public RuntimeWrappedException(Object thrownObject)
+            : base(SR.RuntimeWrappedException)
+        {
+            HResult = HResults.COR_E_RUNTIMEWRAPPED;
+            _wrappedException = thrownObject;
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+        }
+
+        public Object WrappedException => _wrappedException;
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/CompilerServices/ValueTaskAwaiter.cs b/src/mscorlib/shared/System/Runtime/CompilerServices/ValueTaskAwaiter.cs
new file mode 100644
index 0000000000..c419482521
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/CompilerServices/ValueTaskAwaiter.cs
@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>Provides an awaiter for a <see cref="ValueTask{TResult}"/>.</summary>
+    public struct ValueTaskAwaiter<TResult> : ICriticalNotifyCompletion
+    {
+        /// <summary>The value being awaited.</summary>
+        private ValueTask<TResult> _value; // Methods are called on this; avoid making it readonly so as to avoid unnecessary copies
+
+        /// <summary>Initializes the awaiter.</summary>
+        /// <param name="value">The value to be awaited.</param>
+        internal ValueTaskAwaiter(ValueTask<TResult> value) => _value = value;
+
+        /// <summary>Gets whether the <see cref="ValueTask{TResult}"/> has completed.</summary>
+        public bool IsCompleted => _value.IsCompleted;
+
+        /// <summary>Gets the result of the ValueTask.</summary>
+        public TResult GetResult() =>
+            _value._task == null ? 
+                _value._result : 
+                _value._task.GetAwaiter().GetResult();
+
+        /// <summary>Schedules the continuation action for this ValueTask.</summary>
+        public void OnCompleted(Action continuation) =>
+            _value.AsTask().ConfigureAwait(continueOnCapturedContext: true).GetAwaiter().OnCompleted(continuation);
+
+        /// <summary>Schedules the continuation action for this ValueTask.</summary>
+        public void UnsafeOnCompleted(Action continuation) =>
+            _value.AsTask().ConfigureAwait(continueOnCapturedContext: true).GetAwaiter().UnsafeOnCompleted(continuation);
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/ExceptionServices/HandleProcessCorruptedStateExceptionsAttribute.cs b/src/mscorlib/shared/System/Runtime/ExceptionServices/HandleProcessCorruptedStateExceptionsAttribute.cs
new file mode 100644
index 0000000000..cc1bc81e5a
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/ExceptionServices/HandleProcessCorruptedStateExceptionsAttribute.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.ExceptionServices
+{
+    // This attribute can be applied to methods to indicate that ProcessCorruptedState
+    // Exceptions should be delivered to them.
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = false)]
+    public sealed class HandleProcessCorruptedStateExceptionsAttribute : Attribute
+    {
+        public HandleProcessCorruptedStateExceptionsAttribute()
+        {
+        }
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/InteropServices/BestFitMappingAttribute.cs b/src/mscorlib/shared/System/Runtime/InteropServices/BestFitMappingAttribute.cs
new file mode 100644
index 0000000000..4ebee1538c
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/InteropServices/BestFitMappingAttribute.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Interface | AttributeTargets.Class | AttributeTargets.Struct, Inherited = false)]
+    public sealed class BestFitMappingAttribute : Attribute
+    {
+        public BestFitMappingAttribute(bool BestFitMapping)
+        {
+            this.BestFitMapping = BestFitMapping;
+        }
+
+        public bool BestFitMapping { get; }
+
+        public bool ThrowOnUnmappableChar;
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/InteropServices/DefaultCharSetAttribute.cs b/src/mscorlib/shared/System/Runtime/InteropServices/DefaultCharSetAttribute.cs
new file mode 100644
index 0000000000..7a486f7017
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/InteropServices/DefaultCharSetAttribute.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Module, Inherited = false)]
+    public sealed class DefaultCharSetAttribute : Attribute
+    {
+        public DefaultCharSetAttribute(CharSet charSet)
+        {
+            CharSet = charSet;
+        }
+
+        public CharSet CharSet { get; }
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/InteropServices/DefaultDllImportSearchPathsAttribute.cs b/src/mscorlib/shared/System/Runtime/InteropServices/DefaultDllImportSearchPathsAttribute.cs
new file mode 100644
index 0000000000..1ff27fbbd5
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/InteropServices/DefaultDllImportSearchPathsAttribute.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Method, AllowMultiple = false)]
+    public sealed class DefaultDllImportSearchPathsAttribute : Attribute
+    {
+        public DefaultDllImportSearchPathsAttribute(DllImportSearchPath paths)
+        {
+            Paths = paths;
+        }
+
+        public DllImportSearchPath Paths { get; }
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/InteropServices/DllImportAttribute.cs b/src/mscorlib/shared/System/Runtime/InteropServices/DllImportAttribute.cs
new file mode 100644
index 0000000000..97f870d49c
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/InteropServices/DllImportAttribute.cs
@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Method, Inherited = false)]
+    public sealed class DllImportAttribute : Attribute
+    {
+        public DllImportAttribute(string dllName)
+        {
+            Value = dllName;
+        }
+
+        public string Value { get; }
+
+        public string EntryPoint;
+        public CharSet CharSet;
+        public bool SetLastError;
+        public bool ExactSpelling;
+        public CallingConvention CallingConvention;
+        public bool BestFitMapping;
+        public bool PreserveSig;
+        public bool ThrowOnUnmappableChar;
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/InteropServices/DllImportSearchPath.cs b/src/mscorlib/shared/System/Runtime/InteropServices/DllImportSearchPath.cs
new file mode 100644
index 0000000000..8dbdb40be9
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/InteropServices/DllImportSearchPath.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [Flags]
+    public enum DllImportSearchPath
+    {
+        UseDllDirectoryForDependencies = 0x100,
+        ApplicationDirectory = 0x200,
+        UserDirectories = 0x400,
+        System32 = 0x800,
+        SafeDirectories = 0x1000,
+        AssemblyDirectory = 0x2,
+        LegacyBehavior = 0x0
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/InteropServices/ExternalException.cs b/src/mscorlib/shared/System/Runtime/InteropServices/ExternalException.cs
index 81b9a46928..0861d19362 100644
--- a/src/mscorlib/shared/System/Runtime/InteropServices/ExternalException.cs
+++ b/src/mscorlib/shared/System/Runtime/InteropServices/ExternalException.cs
@@ -26,19 +26,19 @@ namespace System.Runtime.InteropServices
         public ExternalException()
             : base(SR.Arg_ExternalException)
         {
-            HResult = __HResults.E_FAIL;
+            HResult = HResults.E_FAIL;
         }
 
         public ExternalException(string message)
             : base(message)
         {
-            HResult = __HResults.E_FAIL;
+            HResult = HResults.E_FAIL;
         }
 
         public ExternalException(string message, Exception inner)
             : base(message, inner)
         {
-            HResult = __HResults.E_FAIL;
+            HResult = HResults.E_FAIL;
         }
 
         public ExternalException(string message, int errorCode)
diff --git a/src/mscorlib/shared/System/Runtime/InteropServices/FieldOffsetAttribute.cs b/src/mscorlib/shared/System/Runtime/InteropServices/FieldOffsetAttribute.cs
new file mode 100644
index 0000000000..27e1097749
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/InteropServices/FieldOffsetAttribute.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Field, Inherited = false)]
+    public sealed class FieldOffsetAttribute : Attribute
+    {
+        public FieldOffsetAttribute(int offset)
+        {
+            Value = offset;
+        }
+
+        public int Value { get; }
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/InteropServices/InAttribute.cs b/src/mscorlib/shared/System/Runtime/InteropServices/InAttribute.cs
new file mode 100644
index 0000000000..39f5a958bc
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/InteropServices/InAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+    public sealed class InAttribute : Attribute
+    {
+        public InAttribute()
+        {
+        }
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/InteropServices/MarshalAsAttribute.cs b/src/mscorlib/shared/System/Runtime/InteropServices/MarshalAsAttribute.cs
new file mode 100644
index 0000000000..4a64050ed1
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/InteropServices/MarshalAsAttribute.cs
@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Parameter | AttributeTargets.Field | AttributeTargets.ReturnValue, Inherited = false)]
+    public sealed class MarshalAsAttribute : Attribute
+    {
+        public MarshalAsAttribute(UnmanagedType unmanagedType)
+        {
+            Value = unmanagedType;
+        }
+        public MarshalAsAttribute(short unmanagedType)
+        {
+            Value = (UnmanagedType)unmanagedType;
+        }
+
+        public UnmanagedType Value { get; }
+
+        // Fields used with SubType = SafeArray.
+        public VarEnum SafeArraySubType;
+        public Type SafeArrayUserDefinedSubType;
+
+        // Field used with iid_is attribute (interface pointers).
+        public int IidParameterIndex;
+
+        // Fields used with SubType = ByValArray and LPArray.
+        // Array size =  parameter(PI) * PM + C
+        public UnmanagedType ArraySubType;
+        public short SizeParamIndex;           // param index PI
+        public int SizeConst;                // constant C
+
+        // Fields used with SubType = CustomMarshaler
+        public string MarshalType;              // Name of marshaler class
+        public Type MarshalTypeRef;           // Type of marshaler class
+        public string MarshalCookie;            // cookie to pass to marshaler
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/InteropServices/OptionalAttribute.cs b/src/mscorlib/shared/System/Runtime/InteropServices/OptionalAttribute.cs
new file mode 100644
index 0000000000..5ac75d7b3e
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/InteropServices/OptionalAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+    public sealed class OptionalAttribute : Attribute
+    {
+        public OptionalAttribute()
+        {
+        }
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/InteropServices/OutAttribute.cs b/src/mscorlib/shared/System/Runtime/InteropServices/OutAttribute.cs
new file mode 100644
index 0000000000..338ceac91e
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/InteropServices/OutAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+    public sealed class OutAttribute : Attribute
+    {
+        public OutAttribute()
+        {
+        }
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/InteropServices/PreserveSigAttribute.cs b/src/mscorlib/shared/System/Runtime/InteropServices/PreserveSigAttribute.cs
new file mode 100644
index 0000000000..464e1abcbe
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/InteropServices/PreserveSigAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Method, Inherited = false)]
+    public sealed class PreserveSigAttribute : Attribute
+    {
+        public PreserveSigAttribute()
+        {
+        }
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/InteropServices/StructLayoutAttribute.cs b/src/mscorlib/shared/System/Runtime/InteropServices/StructLayoutAttribute.cs
new file mode 100644
index 0000000000..c4cce9956e
--- /dev/null
+++ b/src/mscorlib/shared/System/Runtime/InteropServices/StructLayoutAttribute.cs
@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct, Inherited = false)]
+    public sealed class StructLayoutAttribute : Attribute
+    {
+        public StructLayoutAttribute(LayoutKind layoutKind)
+        {
+            Value = layoutKind;
+        }
+
+        public StructLayoutAttribute(short layoutKind)
+        {
+            Value = (LayoutKind)layoutKind;
+        }
+
+        public LayoutKind Value { get; }
+
+        public int Pack;
+        public int Size;
+        public CharSet CharSet;
+    }
+}
diff --git a/src/mscorlib/shared/System/Runtime/InteropServices/UnmanagedFunctionPointerAttribute.cs b/src/mscorlib/shared/System/Runtime/InteropServices/UnmanagedFunctionPointerAttribute.cs
index 2d69c95afe..c4f96903ee 100644
--- a/src/mscorlib/shared/System/Runtime/InteropServices/UnmanagedFunctionPointerAttribute.cs
+++ b/src/mscorlib/shared/System/Runtime/InteropServices/UnmanagedFunctionPointerAttribute.cs
@@ -7,11 +7,6 @@ namespace System.Runtime.InteropServices
     [AttributeUsage(AttributeTargets.Delegate, AllowMultiple = false, Inherited = false)]
     public sealed class UnmanagedFunctionPointerAttribute : Attribute
     {
-        public bool BestFitMapping;
-        public bool SetLastError;
-        public bool ThrowOnUnmappableChar;
-        public CharSet CharSet;
-
         public UnmanagedFunctionPointerAttribute()
         {
             CallingConvention = CallingConvention.Winapi;
@@ -23,5 +18,10 @@ namespace System.Runtime.InteropServices
         }
 
         public CallingConvention CallingConvention { get; }
+
+        public bool BestFitMapping;
+        public bool SetLastError;
+        public bool ThrowOnUnmappableChar;
+        public CharSet CharSet;
     }
 }
diff --git a/src/mscorlib/shared/System/Runtime/Serialization/SerializationException.cs b/src/mscorlib/shared/System/Runtime/Serialization/SerializationException.cs
index bfe3313659..3e0af092c0 100644
--- a/src/mscorlib/shared/System/Runtime/Serialization/SerializationException.cs
+++ b/src/mscorlib/shared/System/Runtime/Serialization/SerializationException.cs
@@ -15,19 +15,19 @@ namespace System.Runtime.Serialization
         public SerializationException()
             : base(s_nullMessage)
         {
-            HResult = __HResults.COR_E_SERIALIZATION;
+            HResult = HResults.COR_E_SERIALIZATION;
         }
 
         public SerializationException(String message)
             : base(message)
         {
-            HResult = __HResults.COR_E_SERIALIZATION;
+            HResult = HResults.COR_E_SERIALIZATION;
         }
 
         public SerializationException(String message, Exception innerException)
             : base(message, innerException)
         {
-            HResult = __HResults.COR_E_SERIALIZATION;
+            HResult = HResults.COR_E_SERIALIZATION;
         }
 
         protected SerializationException(SerializationInfo info, StreamingContext context)