Nullable annotations part 4 (final) (#2300)

* Nullable annotations part 4 (final)

* PR feedback

- Clean up extra variables introduced as
  nullable versions of existing variables.

* Fix a few annotations

- TryGetMethodStubValue may return null when true
- GetReturnType and GetParameterType may return null in some cases

* More annotations and PR feedback

- Don't resolve a generic typeref that should already be a typedef
- Remove some redundant null checks
- Turn on nullable annotations for ref assembly
- Remove #nullable disable section

* Clean up GetInflatedDeclaringType

- Remove null check
- Replace TryResolve call with an assert
- Add comment and asserts justifying null-forgiving operator

* Replace exception with assert in accessors

* PR feedback

- Add parens to improve readability
- Throw on diagnostic without message
- Remove unnecessary string.empty

* Undo DiagnosticString change

- Some DiagnosticIds intentionally have no fixed format strings because
  we generate different strings in different circumstances.

2 files changed, 8 insertions, 8 deletions

diff --git a/test/ILLink.Tasks.Tests/ILLink.Tasks.Tests.cs b/test/ILLink.Tasks.Tests/ILLink.Tasks.Tests.cs
index dbf9bb427..216dec205 100644
--- a/test/ILLink.Tasks.Tests/ILLink.Tasks.Tests.cs
+++ b/test/ILLink.Tasks.Tests/ILLink.Tasks.Tests.cs
@@ -382,7 +382,7 @@ namespace ILLink.Tasks.Tests
 				}
 			}
 		}
-#nullable disable
+#nullable restore
 
 		public static IEnumerable<object[]> CustomDataCases => new List<object[]> {
 			new object [] {
diff --git a/test/ILLink.Tasks.Tests/Mock.cs b/test/ILLink.Tasks.Tests/Mock.cs
index 681834087..dba28887b 100644
--- a/test/ILLink.Tasks.Tests/Mock.cs
+++ b/test/ILLink.Tasks.Tests/Mock.cs
@@ -101,13 +101,13 @@ namespace ILLink.Tasks.Tests
 			SetupContext (Logger);
 		}
 
-		public LinkContext Context => context;
+		public new LinkContext Context => base.Context;
 
 		public CustomLogger Logger { get; private set; }
 
 		public IEnumerable<string> GetRootAssemblies ()
 		{
-			foreach (var step in context.Pipeline.GetSteps ()) {
+			foreach (var step in Context.Pipeline.GetSteps ()) {
 				if (!(step is RootAssemblyInput))
 					continue;
 
@@ -121,7 +121,7 @@ namespace ILLink.Tasks.Tests
 
 		public IEnumerable<string> GetRootDescriptors ()
 		{
-			foreach (var step in context.Pipeline.GetSteps ()) {
+			foreach (var step in Context.Pipeline.GetSteps ()) {
 				if (!(step is ResolveFromXmlStep))
 					continue;
 
@@ -133,7 +133,7 @@ namespace ILLink.Tasks.Tests
 
 		public IEnumerable<string> GetReferenceAssemblies ()
 		{
-			return (IEnumerable<string>) typeof (AssemblyResolver).GetField ("_references", BindingFlags.NonPublic | BindingFlags.Instance).GetValue (context.Resolver);
+			return (IEnumerable<string>) typeof (AssemblyResolver).GetField ("_references", BindingFlags.NonPublic | BindingFlags.Instance).GetValue (Context.Resolver);
 		}
 
 		protected override void AddResolveFromXmlStep (Pipeline pipeline, string file)
@@ -150,7 +150,7 @@ namespace ILLink.Tasks.Tests
 
 		public IEnumerable<IDependencyRecorder> GetDependencyRecorders ()
 		{
-			return (IEnumerable<IDependencyRecorder>) typeof (Tracer).GetField ("recorders", BindingFlags.NonPublic | BindingFlags.Instance).GetValue (context.Tracer);
+			return (IEnumerable<IDependencyRecorder>) typeof (Tracer).GetField ("recorders", BindingFlags.NonPublic | BindingFlags.Instance).GetValue (Context.Tracer);
 		}
 
 		public new bool GetOptimizationName (string optimization, out CodeOptimizations codeOptimizations)
@@ -160,13 +160,13 @@ namespace ILLink.Tasks.Tests
 
 		public CodeOptimizations GetDefaultOptimizations ()
 		{
-			return context.Optimizations.Global;
+			return Context.Optimizations.Global;
 		}
 
 		public Dictionary<string, string> GetCustomData ()
 		{
 			var field = typeof (LinkContext).GetField ("_parameters", BindingFlags.NonPublic | BindingFlags.Instance);
-			return (Dictionary<string, string>) field.GetValue (this.context);
+			return (Dictionary<string, string>) field.GetValue (Context);
 		}
 
 		protected override List<BaseStep> CreateDefaultResolvers ()