Add ConstantExpectedAttribute

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -253,6 +253,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)System\Decimal.DecCalc.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\DefaultBinder.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Delegate.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\CodeAnalysis\ConstantExpectedAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\CodeAnalysis\RequiresAssemblyFilesAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\CodeAnalysis\RequiresDynamicCodeAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\CodeAnalysis\RequiresUnreferencedCodeAttribute.cs" />

src/libraries/System.Private.CoreLib/src/System/Diagnostics/CodeAnalysis/ConstantExpectedAttribute.cs

@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Diagnostics.CodeAnalysis
+{
+    /// <summary>
+    /// Indicates that the specified method parameter expects a constant
+    /// </summary>
+    /// <remarks>
+    /// This can be used to inform tooling that a constant should be used as an argument for the annotated parameter
+    /// </remarks>
+    [AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false, Inherited = false)]
+    public sealed class ConstantExpectedAttribute : Attribute
+    {
+        /// <summary>
+        /// Indicates the minimum bound of the expected constant, inclusive.
+        /// </summary>
+        public object? Min { get; set; }
+        /// <summary>
+        /// Indicates the maximum bound of the expected constant, inclusive.
+        /// </summary>
+        public object? Max { get; set; }
+    }
+}

src/libraries/System.Runtime/ref/System.Runtime.cs

@@ -9041,6 +9041,12 @@ public sealed partial class AllowNullAttribute : System.Attribute
     {
         public AllowNullAttribute() { }
     }
+    [System.AttributeUsageAttribute(System.AttributeTargets.Parameter, Inherited=false)]
+    public sealed class ConstantExpectedAttribute : Attribute
+    {
+        public object? Min { get { throw null; } set { } }
+        public object? Max { get { throw null; } set { } }
+    }
     [System.AttributeUsageAttribute(System.AttributeTargets.Field | System.AttributeTargets.Parameter | System.AttributeTargets.Property, Inherited=false)]
     public sealed partial class DisallowNullAttribute : System.Attribute
     {

src/libraries/System.Runtime/tests/System.Runtime.Tests.csproj

@@ -154,6 +154,7 @@
     <Compile Include="System\ComponentModel\DefaultValueAttributeTests.cs" />
     <Compile Include="System\ComponentModel\EditorBrowsableAttributeTests.cs" />
     <Compile Include="System\Diagnostics\ConditionalAttributeTests.cs" />
+    <Compile Include="System\Diagnostics\CodeAnalysis\ConstantExpectedAttributeTests.cs" />
     <Compile Include="System\Diagnostics\CodeAnalysis\DynamicallyAccessedMembersAttributeTests.cs" />
     <Compile Include="System\Diagnostics\CodeAnalysis\DynamicDependencyAttributeTests.cs" />
     <Compile Include="System\Diagnostics\CodeAnalysis\RequiresAssemblyFilesAttributeTests.cs" />

src/libraries/System.Runtime/tests/System/Diagnostics/CodeAnalysis/ConstantExpectedAttributeTests.cs

@@ -0,0 +1,70 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Xunit;
+
+namespace System.Diagnostics.CodeAnalysis.Tests
+{
+    public class ConstantExpectedAttributeTests
+    {
+        [Fact]
+        public void TestConstructor()
+        {
+            var attr = new ConstantExpectedAttribute();
+
+            Assert.Null(attr.Min);
+            Assert.Null(attr.Max);
+        }
+
+        [Theory]
+        [InlineData("https://dot.net")]
+        [InlineData("")]
+        [InlineData(10000)]
+        [InlineData(0.5f)]
+        [InlineData(null)]
+        public void TestSetMin(object min)
+        {
+            var attr = new ConstantExpectedAttribute
+            {
+                Min = min
+            };
+
+            Assert.Same(min, attr.Min);
+        }
+
+        [Theory]
+        [InlineData("https://dot.net")]
+        [InlineData("")]
+        [InlineData(10000)]
+        [InlineData(0.5f)]
+        [InlineData(null)]
+        public void TestSetMax(object max)
+        {
+            var attr = new ConstantExpectedAttribute
+            {
+                Max = max
+            };
+
+            Assert.Same(max, attr.Max);
+        }
+
+        [Theory]
+        [InlineData("", "https://dot.net")]
+        [InlineData(10000, 20000)]
+        [InlineData(0.5f, 2.0f)]
+        [InlineData(null, null)]
+        [InlineData(10, 0)]
+        [InlineData(10, "https://dot.net")]
+        public void TestSetMinAndMax(object min, object max)
+        {
+            var attr = new ConstantExpectedAttribute
+            {
+                Min = min,
+                Max = max
+            };
+
+            Assert.Same(min, attr.Min);
+            Assert.Same(max, attr.Max);
+        }
+    }
+}