3 files changed, 16 insertions, 11 deletions

diff --git a/src/linker/Linker.Dataflow/AttributeDataFlow.cs b/src/linker/Linker.Dataflow/AttributeDataFlow.cs
index 357803a76..3ed11d392 100644
--- a/src/linker/Linker.Dataflow/AttributeDataFlow.cs
+++ b/src/linker/Linker.Dataflow/AttributeDataFlow.cs
@@ -50,6 +50,9 @@ namespace Mono.Linker.Dataflow
 		MultiValue GetValueForCustomAttributeArgument (CustomAttributeArgument argument)
 		{
 			if (argument.Type.Name == "Type") {
+				if (argument.Value is null)
+					return NullValue.Instance;
+
 				TypeDefinition? referencedType = ((TypeReference) argument.Value).ResolveToTypeDefinition (_context);
 				return referencedType == null
 					? UnknownValue.Instance
@@ -57,7 +60,7 @@ namespace Mono.Linker.Dataflow
 			}
 
 			if (argument.Type.MetadataType == MetadataType.String)
-				return new KnownStringValue ((string) argument.Value);
+				return argument.Value is null ? NullValue.Instance : new KnownStringValue ((string) argument.Value);
 
 			// We shouldn't have gotten a non-null annotation for this from GetParameterAnnotation
 			throw new InvalidOperationException ();
diff --git a/src/linker/Linker.Dataflow/CompilerGeneratedCallGraph.cs b/src/linker/Linker.Dataflow/CompilerGeneratedCallGraph.cs
index 551ff51e5..1cfbc8770 100644
--- a/src/linker/Linker.Dataflow/CompilerGeneratedCallGraph.cs
+++ b/src/linker/Linker.Dataflow/CompilerGeneratedCallGraph.cs
@@ -9,15 +9,15 @@ namespace Mono.Linker.Dataflow
 {
 	sealed class CompilerGeneratedCallGraph
 	{
-		readonly Dictionary<IMemberDefinition, HashSet<IMemberDefinition>> callGraph;
+		readonly Dictionary<IMemberDefinition, HashSet<IMemberDefinition>> _callGraph;
 
-		public CompilerGeneratedCallGraph () => callGraph = new Dictionary<IMemberDefinition, HashSet<IMemberDefinition>> ();
+		public CompilerGeneratedCallGraph () => _callGraph = new Dictionary<IMemberDefinition, HashSet<IMemberDefinition>> ();
 
 		void TrackCallInternal (IMemberDefinition fromMember, IMemberDefinition toMember)
 		{
-			if (!callGraph.TryGetValue (fromMember, out HashSet<IMemberDefinition>? toMembers)) {
+			if (!_callGraph.TryGetValue (fromMember, out HashSet<IMemberDefinition>? toMembers)) {
 				toMembers = new HashSet<IMemberDefinition> ();
-				callGraph.Add (fromMember, toMembers);
+				_callGraph.Add (fromMember, toMembers);
 			}
 			toMembers.Add (toMember);
 		}
@@ -48,7 +48,7 @@ namespace Mono.Linker.Dataflow
 			visited.Add (start);
 			queue.Enqueue (start);
 			while (queue.TryDequeue (out IMemberDefinition? method)) {
-				if (!callGraph.TryGetValue (method, out HashSet<IMemberDefinition>? callees))
+				if (!_callGraph.TryGetValue (method, out HashSet<IMemberDefinition>? callees))
 					continue;
 
 				foreach (var callee in callees) {
diff --git a/src/linker/Linker.Dataflow/CompilerGeneratedState.cs b/src/linker/Linker.Dataflow/CompilerGeneratedState.cs
index 2802e6703..c99968f1d 100644
--- a/src/linker/Linker.Dataflow/CompilerGeneratedState.cs
+++ b/src/linker/Linker.Dataflow/CompilerGeneratedState.cs
@@ -102,7 +102,7 @@ namespace Mono.Linker.Dataflow
 		/// up and find the nearest containing user type. Returns the nearest user type,
 		/// or null if none was found.
 		/// </summary>
-		TypeDefinition? PopulateCacheForType (TypeDefinition type)
+		TypeDefinition? GetCompilerGeneratedStateForType (TypeDefinition type)
 		{
 			// Look in the declaring type if this is a compiler-generated type (state machine or display class).
 			// State machines can be emitted into display classes, so we may also need to go one more level up.
@@ -183,7 +183,7 @@ namespace Mono.Linker.Dataflow
 					}
 					// Already warned above if multiple methods map to the same type
 					// Fill in null for argument providers now, the real providers will be filled in later
-					_ = _generatedTypeToTypeArgumentInfo.TryAdd (stateMachineType, new TypeArgumentInfo (method, null));
+					_generatedTypeToTypeArgumentInfo[stateMachineType] = new TypeArgumentInfo (method, null);
 				}
 			}
 
@@ -292,6 +292,7 @@ namespace Mono.Linker.Dataflow
 					if (typeRef is null) {
 						return;
 					}
+
 					for (int i = 0; i < typeRef.GenericArguments.Count; i++) {
 						var typeArg = typeRef.GenericArguments[i];
 						// Start with the existing parameters, in case we can't find the mapped one
@@ -321,6 +322,7 @@ namespace Mono.Linker.Dataflow
 
 						typeArgs[i] = userAttrs;
 					}
+
 					_generatedTypeToTypeArgumentInfo[generatedType] = typeInfo with { OriginalAttributes = typeArgs };
 				}
 			}
@@ -356,7 +358,7 @@ namespace Mono.Linker.Dataflow
 			if (IsNestedFunctionOrStateMachineMember (method))
 				return false;
 
-			var typeToCache = PopulateCacheForType (method.DeclaringType);
+			var typeToCache = GetCompilerGeneratedStateForType (method.DeclaringType);
 			if (typeToCache is null)
 				return false;
 
@@ -371,7 +373,7 @@ namespace Mono.Linker.Dataflow
 		{
 			Debug.Assert (CompilerGeneratedNames.IsGeneratedType (generatedType.Name));
 
-			var typeToCache = PopulateCacheForType (generatedType);
+			var typeToCache = GetCompilerGeneratedStateForType (generatedType);
 			if (typeToCache is null)
 				return null;
 
@@ -407,7 +409,7 @@ namespace Mono.Linker.Dataflow
 			// sourceType is a state machine type, or the type containing a lambda or local function.
 			// Search all methods to find the one which points to the type as its
 			// state machine implementation.
-			var typeToCache = PopulateCacheForType (sourceType);
+			var typeToCache = GetCompilerGeneratedStateForType (sourceType);
 			if (typeToCache is null)
 				return false;