Updated to use C#7.2 to leverage updated language features. (#39)

Future updates will further leverage the private protected

Author: smaillet

src/Llvm.NET/Llvm.NET.csproj

@@ -13,7 +13,7 @@
         <Description>.NET Bindings for LLVM</Description>
         <PackageTags>LLVM,Compiler,JIT</PackageTags>
         <NoPackageAnalysis>true</NoPackageAnalysis>
-        <LangVersion>7.1</LangVersion>
+        <LangVersion>7.2</LangVersion>
     </PropertyGroup>
     <ItemGroup>
       <Compile Remove="obj\**" />

src/Llvm.NET/Metadata/LlvmMetadata.cs

@@ -46,29 +46,25 @@ public override string ToString( )
 
         internal LLVMMetadataRef MetadataHandle { get; /*protected*/ set; }
 
-        // ideally this would be protected AND internal but C#
-        // doesn't have any syntax to allow such a thing on a constructor
-        // so it is internal and internal code should ensure it is
-        // only ever used by derived type constructors
-        /*protected*/ internal LlvmMetadata( LLVMMetadataRef handle )
+        internal static T FromHandle<T>( Context context, LLVMMetadataRef handle )
+            where T : LlvmMetadata
         {
             if( handle == default )
             {
-                throw new ArgumentNullException( nameof( handle ) );
+                return null;
             }
 
-            MetadataHandle = handle;
+            return ( T )context.GetNodeFor( handle, StaticFactory );
         }
 
-        internal static T FromHandle<T>( Context context, LLVMMetadataRef handle )
-            where T : LlvmMetadata
+        private protected LlvmMetadata( LLVMMetadataRef handle )
         {
             if( handle == default )
             {
-                return null;
+                throw new ArgumentNullException( nameof( handle ) );
             }
 
-            return ( T )context.GetNodeFor( handle, StaticFactory );
+            MetadataHandle = handle;
         }
 
         /// <summary>Enumeration to define debug information metadata nodes</summary>