Fix compile errors.

Author: teo-tsirpanis

src/libraries/Microsoft.Bcl.Memory/src/Microsoft.Bcl.Memory.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppPrevious);$(NetCoreAppMinimum);netstandard2.1;netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
@@ -29,8 +29,10 @@
 
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' != '.NETCoreApp'">
     <Compile Include="Polyfills\System.Numerics.BitOperations.netstandard20.cs" />
+    <Compile Include="System\ThrowHelper.cs" />
     <Compile Include="$(CoreLibSharedDir)System\Text\Ascii.Utility.cs" Link="System\Text\Ascii.Utility.cs" />
     <Compile Include="$(CoreLibSharedDir)System\Text\Ascii.Utility.Helpers.cs" Link="System\Text\Ascii.Utility.Helpers.cs" />
+    <Compile Include="$(CoreLibSharedDir)System\Text\Rune.cs" Link="System\Text\Rune.cs" />
     <Compile Include="$(CoreLibSharedDir)System\Text\UnicodeDebug.cs" Link="System\Text\UnicodeDebug.cs" />
     <Compile Include="$(CoreLibSharedDir)System\Text\UnicodeUtility.cs" Link="System\Text\UnicodeUtility.cs" />
     <Compile Include="$(CoreLibSharedDir)System\Text\Unicode\Utf16Utility.cs" Link="System\Text\Unicode\Utf16Utility.cs" />

src/libraries/Microsoft.Bcl.Memory/src/System/ThrowHelper.cs

@@ -0,0 +1,62 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+
+namespace System
+{
+    internal static class ThrowHelper
+    {
+        [DoesNotReturn]
+        internal static void ThrowArgumentException_DestinationTooShort()
+        {
+            throw new ArgumentException(SR.Argument_DestinationTooShort, "destination");
+        }
+
+        [DoesNotReturn]
+        internal static void ThrowArgumentNullException(ExceptionArgument argument)
+        {
+            throw new ArgumentNullException(GetArgumentName(argument));
+        }
+
+        [DoesNotReturn]
+        internal static void ThrowArgumentOutOfRangeException(ExceptionArgument argument)
+        {
+            throw new ArgumentOutOfRangeException(GetArgumentName(argument));
+        }
+
+        private static string GetArgumentName(ExceptionArgument argument)
+        {
+            switch (argument)
+            {
+                case ExceptionArgument.ch:
+                    return nameof(ExceptionArgument.ch);
+                case ExceptionArgument.culture:
+                    return nameof(ExceptionArgument.culture);
+                case ExceptionArgument.index:
+                    return nameof(ExceptionArgument.index);
+                case ExceptionArgument.input:
+                    return nameof(ExceptionArgument.input);
+                case ExceptionArgument.value:
+                    return nameof(ExceptionArgument.value);
+                default:
+                    Debug.Fail("The enum value is not defined, please check the ExceptionArgument Enum.");
+                    return "";
+
+            }
+        }
+    }
+
+    //
+    // The convention for this enum is using the argument name as the enum name
+    //
+    internal enum ExceptionArgument
+    {
+        ch,
+        culture,
+        index,
+        input,
+        value,
+    }
+}

src/libraries/System.Private.CoreLib/src/System/Text/Rune.cs

@@ -781,6 +781,7 @@ public int EncodeToUtf8(Span<byte> destination)
 
         public override int GetHashCode() => Value;
 
+#if !MICROSOFT_BCL_MEMORY
         /// <summary>
         /// Gets the <see cref="Rune"/> which begins at index <paramref name="index"/> in
         /// string <paramref name="input"/>.
@@ -799,6 +800,7 @@ public static Rune GetRuneAt(string input, int index)
 
             return UnsafeCreate((uint)runeValue);
         }
+#endif
 
         /// <summary>
         /// Returns <see langword="true"/> iff <paramref name="value"/> is a valid Unicode scalar
@@ -850,6 +852,7 @@ internal static int ReadFirstRuneFromUtf16Buffer(ReadOnlySpan<char> input)
             return (int)returnValue;
         }
 
+#if !MICROSOFT_BCL_MEMORY
         // returns a negative number on failure
         private static int ReadRuneFromString(string input, int index)
         {
@@ -897,6 +900,7 @@ private static int ReadRuneFromString(string input, int index)
 
             return (int)returnValue;
         }
+#endif
 
         /// <summary>
         /// Returns a <see cref="string"/> representation of this <see cref="Rune"/> instance.
@@ -1128,6 +1132,7 @@ private static bool TryEncodeToUtf8(Rune value, Span<byte> destination, out int
             return false;
         }
 
+#if !MICROSOFT_BCL_MEMORY
         /// <summary>
         /// Attempts to get the <see cref="Rune"/> which begins at index <paramref name="index"/> in
         /// string <paramref name="input"/>.
@@ -1151,6 +1156,7 @@ public static bool TryGetRuneAt(string input, int index, out Rune value)
                 return false;
             }
         }
+#endif
 
         // Allows constructing a Unicode scalar value from an arbitrary 32-bit integer without
         // validation. It is the caller's responsibility to have performed manual validation