Merge pull request #45090 from sharwell/unused-main

Exclude entry points from unused members analysis
dotnet · Jun 12, 2020 · 6db6c5e · 6db6c5e
2 parents f943a1a + 5cc698b
commit 6db6c5e
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diff --git a/src/Analyzers/CSharp/Tests/RemoveUnusedMembers/RemoveUnusedMembersTests.cs b/src/Analyzers/CSharp/Tests/RemoveUnusedMembers/RemoveUnusedMembersTests.cs
@@ -5,6 +5,8 @@
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CSharp.RemoveUnusedMembers;
+using Microsoft.CodeAnalysis.CSharp.Shared.Extensions;
+using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Test.Utilities;
 using Microsoft.CodeAnalysis.Testing;
 using Roslyn.Test.Utilities;
@@ -356,6 +358,113 @@ class MyClass
             await VerifyCS.VerifyCodeFixAsync(code, code);
         }
 
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnusedMembers)]
+        public async Task EntryPointMethodNotFlagged_06()
+        {
+            var code = @"
+return 0;
+";
+
+            await new VerifyCS.Test
+            {
+                TestCode = code,
+                FixedCode = code,
+                ExpectedDiagnostics =
+                {
+                    // error CS8805: Program using top-level statements must be an executable.
+                    DiagnosticResult.CompilerError("CS8805"),
+                },
+                LanguageVersion = LanguageVersionExtensions.CSharp9,
+            }.RunAsync();
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnusedMembers)]
+        public async Task EntryPointMethodNotFlagged_07()
+        {
+            var code = @"
+return 0;
+";
+
+            await new VerifyCS.Test
+            {
+                TestState =
+                {
+                    Sources = { code, code },
+                },
+                FixedState =
+                {
+                    Sources = { code, code },
+                },
+                ExpectedDiagnostics =
+                {
+                    // error CS8805: Program using top-level statements must be an executable.
+                    DiagnosticResult.CompilerError("CS8805"),
+                    // /0/Test1.cs(2,1): error CS8802: Only one compilation unit can have top-level statements.
+                    DiagnosticResult.CompilerError("CS8802").WithSpan("/0/Test1.cs", 2, 1, 2, 7),
+                },
+                LanguageVersion = LanguageVersionExtensions.CSharp9,
+            }.RunAsync();
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnusedMembers)]
+        public async Task EntryPointMethodNotFlagged_08()
+        {
+            var code = @"
+return 0;
+";
+
+            await new VerifyCS.Test
+            {
+                TestCode = code,
+                FixedCode = code,
+                SolutionTransforms =
+                {
+                    (solution, projectId) =>
+                    {
+                        var project = solution.GetRequiredProject(projectId);
+                        var compilationOptions = project.CompilationOptions;
+                        return solution.WithProjectCompilationOptions(projectId, compilationOptions.WithOutputKind(OutputKind.ConsoleApplication));
+                    },
+                },
+                LanguageVersion = LanguageVersionExtensions.CSharp9,
+            }.RunAsync();
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnusedMembers)]
+        public async Task EntryPointMethodNotFlagged_09()
+        {
+            var code = @"
+return 0;
+";
+
+            await new VerifyCS.Test
+            {
+                TestState =
+                {
+                    Sources = { code, code },
+                },
+                FixedState =
+                {
+                    Sources = { code, code },
+                },
+                ExpectedDiagnostics =
+                {
+                    // /0/Test1.cs(2,1): error CS8802: Only one compilation unit can have top-level statements.
+                    DiagnosticResult.CompilerError("CS8802").WithSpan("/0/Test1.cs", 2, 1, 2, 7),
+                },
+                SolutionTransforms =
+                {
+                    (solution, projectId) =>
+                    {
+                        var project = solution.GetRequiredProject(projectId);
+                        var compilationOptions = project.CompilationOptions;
+                        return solution.WithProjectCompilationOptions(projectId, compilationOptions.WithOutputKind(OutputKind.ConsoleApplication));
+                    },
+                },
+                LanguageVersion = LanguageVersionExtensions.CSharp9,
+            }.RunAsync();
+        }
+
         [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnusedMembers)]
         public async Task FieldIsUnused_ReadOnly()
         {

diff --git a/...yzers/Core/Analyzers/RemoveUnusedMembers/AbstractRemoveUnusedMembersDiagnosticAnalyzer.cs b/...yzers/Core/Analyzers/RemoveUnusedMembers/AbstractRemoveUnusedMembersDiagnosticAnalyzer.cs
@@ -382,9 +382,16 @@ private void OnSymbolEnd(SymbolAnalysisContext symbolEndContext, bool hasUnsuppo
                 ArrayBuilder<string> debuggerDisplayAttributeArguments = null;
                 try
                 {
+                    var entryPoint = symbolEndContext.Compilation.GetEntryPoint(symbolEndContext.CancellationToken);
+
                     var namedType = (INamedTypeSymbol)symbolEndContext.Symbol;
                     foreach (var member in namedType.GetMembers())
                     {
+                        if (SymbolEqualityComparer.Default.Equals(entryPoint, member))
+                        {
+                            continue;
+                        }
+
                         // Check if the underlying member is neither read nor a readable reference to the member is taken.
                         // If so, we flag the member as either unused (never written) or unread (written but not read).
                         if (TryRemove(member, out var valueUsageInfo) &&
@@ -689,7 +696,7 @@ private bool IsCandidateSymbol(ISymbol memberSymbol)
             }
 
             private bool IsEntryPoint(IMethodSymbol methodSymbol)
-                => methodSymbol.Name == WellKnownMemberNames.EntryPointMethodName &&
+                => (methodSymbol.Name == WellKnownMemberNames.EntryPointMethodName || methodSymbol.Name == "$Main") &&
                    methodSymbol.IsStatic &&
                    (methodSymbol.ReturnsVoid ||
                     methodSymbol.ReturnType.SpecialType == SpecialType.System_Int32 ||