From cc63319000132eeb68f91f12fe1daf7a53fe168a Mon Sep 17 00:00:00 2001
From: Andrew Arnott <andrew.arnott@microsoft.com>
Date: Mon, 23 Oct 2023 20:48:33 -0600
Subject: [PATCH] Fix VSTHRD012 false positive due to inaccessible overloads

Fixes #1111
---
 ...AbstractVSTHRD012SpecifyJtfWhereAllowed.cs |  6 +-
 .../Utils.cs                                  | 16 ++++++
 .../VSTHRD012SpecifyJtfWhereAllowedTests.cs   | 57 +++++++++++++++++++
 3 files changed, 77 insertions(+), 2 deletions(-)

diff --git a/src/Microsoft.VisualStudio.Threading.Analyzers/AbstractVSTHRD012SpecifyJtfWhereAllowed.cs b/src/Microsoft.VisualStudio.Threading.Analyzers/AbstractVSTHRD012SpecifyJtfWhereAllowed.cs
index 338f1f5b5..969e32176 100644
--- a/src/Microsoft.VisualStudio.Threading.Analyzers/AbstractVSTHRD012SpecifyJtfWhereAllowed.cs
+++ b/src/Microsoft.VisualStudio.Threading.Analyzers/AbstractVSTHRD012SpecifyJtfWhereAllowed.cs
@@ -81,8 +81,10 @@ private static void AnalyzeCall(OperationAnalysisContext context, Location locat
             // The method being invoked doesn't take any JTC/JTF parameters.
             // Look for an overload that does.
             bool preferableAlternativesExist = otherOverloads
-                .Where(m => !m.IsObsolete())
-                .Any(m => m.Parameters.Skip(m.IsExtensionMethod ? 1 : 0).Any(IsImportantJtfParameter));
+                .Any(m =>
+                    !m.IsObsolete() &&
+                    m.Parameters.Skip(m.IsExtensionMethod ? 1 : 0).Any(IsImportantJtfParameter) &&
+                    context.ContainingSymbol.FindContainingNamedOrAssemblySymbol() is ISymbol containingSymbol && context.Compilation.IsSymbolAccessibleWithin(m, containingSymbol));
             if (preferableAlternativesExist)
             {
                 Diagnostic diagnostic = Diagnostic.Create(
diff --git a/src/Microsoft.VisualStudio.Threading.Analyzers/Utils.cs b/src/Microsoft.VisualStudio.Threading.Analyzers/Utils.cs
index 7ef775888..77d0cc712 100644
--- a/src/Microsoft.VisualStudio.Threading.Analyzers/Utils.cs
+++ b/src/Microsoft.VisualStudio.Threading.Analyzers/Utils.cs
@@ -700,6 +700,22 @@ internal static IOperation FindFinalAncestor(IOperation operation)
         return default;
     }
 
+    internal static ISymbol? FindContainingNamedOrAssemblySymbol(this ISymbol? symbol)
+    {
+        ISymbol? candidate = symbol;
+        while (candidate is not null)
+        {
+            if (candidate is INamedTypeSymbol or IAssemblySymbol)
+            {
+                return candidate;
+            }
+
+            candidate = candidate.ContainingSymbol;
+        }
+
+        return null;
+    }
+
     private static bool IsSymbolTheRightType(ISymbol symbol, string typeName, IReadOnlyList<string> namespaces)
     {
         var fieldSymbol = symbol as IFieldSymbol;
diff --git a/test/Microsoft.VisualStudio.Threading.Analyzers.Tests/VSTHRD012SpecifyJtfWhereAllowedTests.cs b/test/Microsoft.VisualStudio.Threading.Analyzers.Tests/VSTHRD012SpecifyJtfWhereAllowedTests.cs
index dce0000a1..a9cfa155a 100644
--- a/test/Microsoft.VisualStudio.Threading.Analyzers.Tests/VSTHRD012SpecifyJtfWhereAllowedTests.cs
+++ b/test/Microsoft.VisualStudio.Threading.Analyzers.Tests/VSTHRD012SpecifyJtfWhereAllowedTests.cs
@@ -254,4 +254,61 @@ void F() {
 
         await CSVerify.VerifyAnalyzerAsync(test);
     }
+
+    [Fact]
+    public async Task InaccessibleMembers_Private_GeneratesNoWarning()
+    {
+        string test = """
+            using System;
+            using Microsoft.VisualStudio.Threading;
+
+            static class Extensions
+            {
+                public static void OnMainThread(Action action) => OnMainThread(null, action);
+
+                private static void OnMainThread(JoinableTaskFactory factory, Action action) => factory.Run(async delegate
+                {
+                    await factory.SwitchToMainThreadAsync();
+                    action();
+                });
+            }
+
+            class Foo
+            {
+                void Bar()
+                {
+                    Extensions.OnMainThread(() => { });
+                }
+            }
+            """;
+
+        await CSVerify.VerifyAnalyzerAsync(test);
+    }
+
+    [Fact]
+    public async Task AccessibleMembers_Private_GeneratesWarning()
+    {
+        string test = """
+            using System;
+            using Microsoft.VisualStudio.Threading;
+
+            static class Extensions
+            {
+                public static void OnMainThread(Action action) => OnMainThread(null, action);
+
+                private static void OnMainThread(JoinableTaskFactory factory, Action action) => factory.Run(async delegate
+                {
+                    await factory.SwitchToMainThreadAsync();
+                    action();
+                });
+
+                static void Bar()
+                {
+                    [|OnMainThread|](() => { });
+                }
+            }
+            """;
+
+        await CSVerify.VerifyAnalyzerAsync(test);
+    }
 }