CompilerGeneratedCodeInPreservedAssembly.cs

// Copyright (c) .NET Foundation and contributors. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

using System.Diagnostics.CodeAnalysis;
using Mono.Linker.Tests.Cases.Expectations.Assertions;
using Mono.Linker.Tests.Cases.Expectations.Metadata;

namespace Mono.Linker.Tests.Cases.DataFlow
{
    // This test tries to hit a case where the entire assembly is preserved (via descriptor, NOT action)
    // meaning we will go and mark all types and members in it.
    // At the same time there's a compiler generated method (local function) which is called from
    // a branch which will be removed due to constant propagation.
    // And also the test is structured such that the caller of the local function is first seen
    // by the compiler generated code caches after its body has been modified.
    [SkipKeptItemsValidation]
    [ExpectedNoWarnings]
    [SetupLinkerArgument("--enable-opt", "ipconstprop")]
    [SetupLinkerDescriptorFile("CompilerGeneratedCodeInPreservedAssembly.xml")]
    [SetupLinkerArgument("--feature", "AlwaysFalse", "false")]
    class CompilerGeneratedCodeInPreservedAssembly
    {
        public static void Main()
        {
            Inner.WithLocalFunctionInner();
            WithLocalFunction();
        }

        class Inner
        {
            // In this case the compiler generated state will see the modified body
            // and thus will see the local function as orphaned.
            // The method will be marked (due to the descriptor), but its data flow processing
            // will be skipped (it's compiler generated).
            // The user method will also not be scanned for data flow since it won't
            // see the local function as its child.
            public static void WithLocalFunctionInner()
            {
                if (AlwaysFalse)
                {
                    LocalWithWarning();
                }

                // Analyzer doesn't implement constant propagation and branch removal, so it reaches this code
                [ExpectedWarning("IL2026", Tool.Analyzer, "Analyzer does not support compiler-generated code warning suppression")]
                void LocalWithWarning()
                {
                    // No warning
                    Requires();
                }
            }
        }

        // In this case the compiler generated state will currently see the original method body
        // so if will treat LocalWithWarning local function as a "callee" of the user method.
        // This will trigger data flow analysis for the WithLocalFunction, but no warning is produced
        // because the local function is never reached during the interprocedural scan.
        public static void WithLocalFunction()
        {
            if (AlwaysFalse)
            {
                LocalWithWarning();
            }

            // Analyzer doesn't implement constant propagation and branch removal, so it reaches this code
            [ExpectedWarning("IL2026", Tool.Analyzer, "Analyzer does not support compiler-generated code warning suppression")]
            void LocalWithWarning()
            {
                Requires();
            }
        }

        [FeatureSwitchDefinition("AlwaysFalse")]
        public static bool AlwaysFalse => false;

        [RequiresUnreferencedCode("RUC")]
        static void Requires() { }
    }
}