renamed Nil to Null

src/Workspaces/Core/Portable/Execution/Asset.cs

@@ -18,7 +18,7 @@ namespace Microsoft.CodeAnalysis.Execution
     /// </summary>
     internal abstract class Asset : ChecksumObject
     {
-        public static readonly Asset Nil = new NullAsset();
+        public static readonly Asset Null = new NullAsset();
 
         public Asset(Checksum checksum, string kind) : base(checksum, kind)
         {
@@ -32,7 +32,7 @@ public Asset(Checksum checksum, string kind) : base(checksum, kind)
         private sealed class NullAsset : Asset
         {
             public NullAsset() :
-                base(Checksum.Nil, WellKnownChecksumObjects.Nil)
+                base(Checksum.Null, WellKnownChecksumObjects.Null)
             {
             }
 

src/Workspaces/Core/Portable/Execution/Checksum.cs

@@ -14,7 +14,7 @@ namespace Microsoft.CodeAnalysis.Execution
     /// </summary>
     internal sealed partial class Checksum : IObjectWritable, IEquatable<Checksum>
     {
-        public static readonly Checksum Nil = new Checksum(ImmutableArray<byte>.Empty);
+        public static readonly Checksum Null = new Checksum(ImmutableArray<byte>.Empty);
 
         private readonly ImmutableArray<byte> _checkSum;
         private int _lazyHash;

src/Workspaces/Core/Portable/Execution/ChecksumObject.cs

@@ -73,7 +73,7 @@ private static Checksum CreateChecksum(string kind, object[] children)
     // TODO: Kind might not actually needed. see whether we can get rid of this
     internal static class WellKnownChecksumObjects
     {
-        public const string Nil = nameof(Nil);
+        public const string Null = nameof(Null);
 
         public const string Projects = nameof(Projects);
         public const string Documents = nameof(Documents);

src/Workspaces/Core/Portable/Execution/ChecksumTreeBuilder.cs

@@ -90,9 +90,11 @@ private async Task<ProjectChecksumObject> CreateProjectChecksumObjectAsync(Proje
 
             var subAssetBuilder = new AssetBuilder(subTreeNode);
 
-            // set Asset.Nil if this particular project doesn't support compiler options
-            var compilationOptions = projectState.CompilationOptions != null ? subAssetBuilder.Build(projectState, projectState.CompilationOptions, cancellationToken) : Asset.Nil;
-            var parseOptions = projectState.ParseOptions != null ? subAssetBuilder.Build(projectState, projectState.ParseOptions, cancellationToken) : Asset.Nil;
+            // set Asset.Null if this particular project doesn't support compiler options.
+            // this one is really bit wierd since project state has both compilation/parse options but only has support compilation. 
+            // for now, we use support compilation for both options
+            var compilationOptions = projectState.SupportsCompilation ? subAssetBuilder.Build(projectState, projectState.CompilationOptions, cancellationToken) : Asset.Null;
+            var parseOptions = projectState.SupportsCompilation ? subAssetBuilder.Build(projectState, projectState.ParseOptions, cancellationToken) : Asset.Null;
 
             return new ProjectChecksumObject(
                 _serializer, info.Checksum, compilationOptions.Checksum, parseOptions.Checksum,

src/Workspaces/Core/Portable/Execution/ChecksumTreeCollection.cs

@@ -73,10 +73,10 @@ public IRootChecksumTreeNode CreateRootTreeNode(SolutionState solutionState)
 
         public ChecksumObject GetChecksumObject(Checksum checksum, CancellationToken cancellationToken)
         {
-            if (checksum == Checksum.Nil)
+            if (checksum == Checksum.Null)
             {
                 // check nil case
-                return Asset.Nil;
+                return Asset.Null;
             }
 
             // search snapshots we have
@@ -114,9 +114,9 @@ public ChecksumObject GetChecksumObject(Checksum checksum, CancellationToken can
                 var result = new Dictionary<Checksum, ChecksumObject>(numberOfChecksumsToSearch);
 
                 // check nil case
-                if (searchingChecksumsLeft.Object.Remove(Checksum.Nil))
+                if (searchingChecksumsLeft.Object.Remove(Checksum.Null))
                 {
-                    result[Checksum.Nil] = Asset.Nil;
+                    result[Checksum.Null] = Asset.Null;
                 }
 
                 // search checksum trees we have

src/Workspaces/Core/Portable/Execution/Serializer.cs

@@ -43,7 +43,7 @@ public T Deserialize<T>(string kind, ObjectReader reader, CancellationToken canc
 
                 switch (kind)
                 {
-                    case WellKnownChecksumObjects.Nil:
+                    case WellKnownChecksumObjects.Null:
                         return default(T);
 
                     case SolutionChecksumObject.Name: