Fix NullReferenceException in Analyzer (#2400)

* Don't check if the parent type has Requires if the member is already a TypeSymbol (fixes null ref)
* Change IsMemberInRequiresScope argument name from containingSymbol to member, since we call this function from several places and does not always contain the containingSymbol
* Add test for nullref
* Fail tests when analyzer throws an exception

Co-authored-by: Sven Boemer <sbomer@gmail.com>

5 files changed, 36 insertions, 14 deletions

diff --git a/test/ILLink.RoslynAnalyzer.Tests/RequiresUnreferencedCodeAnalyzerTests.cs b/test/ILLink.RoslynAnalyzer.Tests/RequiresUnreferencedCodeAnalyzerTests.cs
index b54b65f8e..d2f8bf64d 100644
--- a/test/ILLink.RoslynAnalyzer.Tests/RequiresUnreferencedCodeAnalyzerTests.cs
+++ b/test/ILLink.RoslynAnalyzer.Tests/RequiresUnreferencedCodeAnalyzerTests.cs
@@ -409,5 +409,20 @@ class C
 
 			return VerifyRequiresUnreferencedCodeAnalyzer (source);
 		}
+
+		[Fact]
+		public Task VerifyThatAnalysisOfFieldsDoesNotNullRef ()
+		{
+			var source = @"
+using System.Diagnostics.CodeAnalysis;
+
+[DynamicallyAccessedMembers (field)]
+class C
+{
+	public const DynamicallyAccessedMemberTypes field = DynamicallyAccessedMemberTypes.PublicMethods;
+}";
+
+			return VerifyRequiresUnreferencedCodeAnalyzer (source);
+		}
 	}
 }
diff --git a/test/ILLink.RoslynAnalyzer.Tests/TestCaseCompilation.cs b/test/ILLink.RoslynAnalyzer.Tests/TestCaseCompilation.cs
index 4c3db2687..edca78bfe 100644
--- a/test/ILLink.RoslynAnalyzer.Tests/TestCaseCompilation.cs
+++ b/test/ILLink.RoslynAnalyzer.Tests/TestCaseCompilation.cs
@@ -1,9 +1,10 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
+using System.Diagnostics;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
@@ -21,14 +22,14 @@ namespace ILLink.RoslynAnalyzer.Tests
 				new RequiresAssemblyFilesAnalyzer (),
 				new RequiresUnreferencedCodeAnalyzer ());
 
-		public static Task<(CompilationWithAnalyzers Compilation, SemanticModel SemanticModel)> CreateCompilation (
+		public static Task<(CompilationWithAnalyzers Compilation, SemanticModel SemanticModel, List<Diagnostic> ExceptionDiagnostics)> CreateCompilation (
 			string src,
 			(string, string)[]? globalAnalyzerOptions = null,
 			IEnumerable<MetadataReference>? additionalReferences = null,
 			IEnumerable<SyntaxTree>? additionalSources = null)
 			=> CreateCompilation (CSharpSyntaxTree.ParseText (src), globalAnalyzerOptions, additionalReferences, additionalSources);
 
-		public static async Task<(CompilationWithAnalyzers Compilation, SemanticModel SemanticModel)> CreateCompilation (
+		public static async Task<(CompilationWithAnalyzers Compilation, SemanticModel SemanticModel, List<Diagnostic> ExceptionDiagnostics)> CreateCompilation (
 			SyntaxTree src,
 			(string, string)[]? globalAnalyzerOptions = null,
 			IEnumerable<MetadataReference>? additionalReferences = null,
@@ -48,18 +49,19 @@ namespace ILLink.RoslynAnalyzer.Tests
 				ImmutableArray<AdditionalText>.Empty,
 				new SimpleAnalyzerOptions (globalAnalyzerOptions));
 
+			var exceptionDiagnostics = new List<Diagnostic> ();
+
 			var compWithAnalyzerOptions = new CompilationWithAnalyzersOptions (
 				analyzerOptions,
-				(_1, _2, _3) => { },
+				(Exception exception, DiagnosticAnalyzer diagnosticAnalyzer, Diagnostic diagnostic) => {
+					exceptionDiagnostics.Add (diagnostic);
+				},
 				concurrentAnalysis: true,
 				logAnalyzerExecutionTime: false);
 
-			return (new CompilationWithAnalyzers (comp, SupportedDiagnosticAnalyzers, compWithAnalyzerOptions), comp.GetSemanticModel (src));
+			return (new CompilationWithAnalyzers (comp, SupportedDiagnosticAnalyzers, compWithAnalyzerOptions), comp.GetSemanticModel (src), exceptionDiagnostics);
 		}
 
-		public static async Task<Compilation> GetCompilation (string source, IEnumerable<MetadataReference>? additionalReferences = null, IEnumerable<SyntaxTree>? additionalSources = null)
-			=> (await CreateCompilation (source, additionalReferences: additionalReferences ?? Array.Empty<MetadataReference> ())).Compilation.Compilation;
-
 		class SimpleAnalyzerOptions : AnalyzerConfigOptionsProvider
 		{
 			public SimpleAnalyzerOptions ((string, string)[]? globalOptions)
diff --git a/test/ILLink.RoslynAnalyzer.Tests/TestCaseUtils.cs b/test/ILLink.RoslynAnalyzer.Tests/TestCaseUtils.cs
index 3cae7cdb7..194a1a96b 100644
--- a/test/ILLink.RoslynAnalyzer.Tests/TestCaseUtils.cs
+++ b/test/ILLink.RoslynAnalyzer.Tests/TestCaseUtils.cs
@@ -52,12 +52,16 @@ namespace ILLink.RoslynAnalyzer.Tests
 
 			var testDependenciesSource = GetTestDependencies (rootSourceDir, tree)
 				.Select (f => SyntaxFactory.ParseSyntaxTree (SourceText.From (File.OpenRead (f))));
-			var (comp, model) = await TestCaseCompilation.CreateCompilation (
+
+			var (comp, model, exceptionDiagnostics) = await TestCaseCompilation.CreateCompilation (
 					tree,
 					msbuildProperties,
 					additionalSources: testDependenciesSource);
 
-			var diags = await comp.GetAnalyzerDiagnosticsAsync ();
+			// Note that the exception diagnostics will be empty until the analyzer has run,
+			// so be sure to get them after awaiting GetAnalyzerDiagnosticsAsync().
+			var diags = (await comp.GetAnalyzerDiagnosticsAsync ()).AddRange (exceptionDiagnostics);
+
 			var testChecker = new TestChecker ((CSharpSyntaxTree) tree, model, diags);
 			testChecker.Check ();
 		}
diff --git a/test/ILLink.RoslynAnalyzer.Tests/TestChecker.cs b/test/ILLink.RoslynAnalyzer.Tests/TestChecker.cs
index e7af1b930..56b5c1e72 100644
--- a/test/ILLink.RoslynAnalyzer.Tests/TestChecker.cs
+++ b/test/ILLink.RoslynAnalyzer.Tests/TestChecker.cs
@@ -33,8 +33,8 @@ namespace ILLink.RoslynAnalyzer.Tests
 			_tree = tree;
 			_semanticModel = semanticModel;
 			_diagnostics = diagnostics
-				// Filter down to diagnostics which originate from this tree
-				.Where (d => d.Location.SourceTree == tree).ToList ();
+				// Filter down to diagnostics which originate from this tree or have no location
+				.Where (d => d.Location.SourceTree == tree || d.Location.SourceTree == null).ToList ();
 
 			// Filled in later
 			_unmatched = new List<Diagnostic> ();
diff --git a/test/ILLink.RoslynAnalyzer.Tests/Verifiers/CSharpAnalyzerVerifier`1.cs b/test/ILLink.RoslynAnalyzer.Tests/Verifiers/CSharpAnalyzerVerifier`1.cs
index 5afc179b8..79800c3f8 100644
--- a/test/ILLink.RoslynAnalyzer.Tests/Verifiers/CSharpAnalyzerVerifier`1.cs
+++ b/test/ILLink.RoslynAnalyzer.Tests/Verifiers/CSharpAnalyzerVerifier`1.cs
@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Diagnostics;
@@ -37,7 +37,8 @@ namespace ILLink.RoslynAnalyzer.Tests
 		/// <inheritdoc cref="AnalyzerVerifier{TAnalyzer, TTest, TVerifier}.VerifyAnalyzerAsync(string, DiagnosticResult[])"/>
 		public static async Task VerifyAnalyzerAsync (string src, (string, string)[]? analyzerOptions = null, IEnumerable<MetadataReference>? additionalReferences = null, params DiagnosticResult[] expected)
 		{
-			var diags = await (await TestCaseCompilation.CreateCompilation (src, analyzerOptions, additionalReferences)).Compilation.GetAllDiagnosticsAsync ();
+			var (comp, _, exceptionDiagnostics) = await TestCaseCompilation.CreateCompilation (src, analyzerOptions, additionalReferences);
+			var diags = (await comp.GetAllDiagnosticsAsync ()).AddRange (exceptionDiagnostics);
 			var analyzers = ImmutableArray.Create<DiagnosticAnalyzer> (new TAnalyzer ());
 			VerifyDiagnosticResults (diags, analyzers, expected, DefaultVerifier);
 		}