Make DependencyModel.Dependency readonly and implement IEquatable<>

src/libraries/Microsoft.Extensions.DependencyModel/ref/Microsoft.Extensions.DependencyModel.cs

@@ -46,10 +46,10 @@ public CompilationOptions(System.Collections.Generic.IEnumerable<string> defines
         public bool? PublicSign { get { throw null; } }
         public bool? WarningsAsErrors { get { throw null; } }
     }
-    public partial struct Dependency
+    public readonly partial struct Dependency : System.IEquatable<Dependency>
     {
-        private object _dummy;
-        private int _dummyPrimitive;
+        private readonly object _dummy;
+        private readonly int _dummyPrimitive;
         public Dependency(string name, string version) { throw null; }
         public readonly string Name { get { throw null; } }
         public readonly string Version { get { throw null; } }

src/libraries/Microsoft.Extensions.DependencyModel/src/Dependency.cs

@@ -6,7 +6,7 @@
 
 namespace Microsoft.Extensions.DependencyModel
 {
-    public struct Dependency
+    public readonly struct Dependency : IEquatable<Dependency>
     {
         public Dependency(string name, string version)
         {
@@ -30,11 +30,7 @@ public bool Equals(Dependency other)
             return string.Equals(Name, other.Name) && string.Equals(Version, other.Version);
         }
 
-        public override bool Equals(object obj)
-        {
-            if (obj is null) return false;
-            return obj is Dependency && Equals((Dependency) obj);
-        }
+        public override bool Equals(object obj) => obj is Dependency dependency && Equals(dependency);
 
         public override int GetHashCode() =>
             HashHelpers.Combine(Name.GetHashCode(), Version.GetHashCode());