Imported Upstream version 6.4.0.137

Former-commit-id: 943baa9f16a098c33e129777827f3a9d20da00d6

mcs/class/System.Private.CoreLib/System/Nullable.cs

@@ -0,0 +1,37 @@
+namespace System
+{
+	partial struct Nullable<T>
+	{
+		//
+		// These are called by the JIT
+		//
+
+		//
+		// JIT implementation of box valuetype System.Nullable`1<T>
+		//
+		static object? Box (T? o)
+		{
+			if (!o.hasValue)
+				return null;
+
+			return o.value;
+		}
+		
+		static T? Unbox (object o)
+		{
+			if (o == null)
+				return null;
+			return (T) o;
+		}
+
+		static T? UnboxExact (object o)
+		{
+			if (o == null)
+				return null;
+			if (o.GetType() != typeof (T))
+				throw new InvalidCastException();
+
+			return (T) o;
+		}
+	}
+}