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Sep 17, 2025
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Ensure that top-level statements entry point emits MethodImplAttributes.Async #80314

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2bb380a
Ensure that top-level statements entry point emits MethodImplAttribut…
333fred Sep 16, 2025
6fc9fe6
Naming
333fred Sep 17, 2025
ce68cdc
Add additional validation for int-returning mains.
333fred Sep 17, 2025
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18 changes: 11 additions & 7 deletions src/Compilers/CSharp/Portable/Symbols/Source/SourceMethodSymbolWithAttributes.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1756,18 +1756,22 @@ internal override System.Reflection.MethodImplAttributes ImplementationAttribute
result |= (System.Reflection.MethodImplAttributes.Runtime | System.Reflection.MethodImplAttributes.InternalCall);
}

if (this.IsAsync && this.DeclaringCompilation.IsRuntimeAsyncEnabledIn(this))
{
// https://github.com/dotnet/roslyn/issues/79792: Use real value from MethodImplAttributes when available
// When a method is emitted using runtime async, we add MethodImplAttributes.Async to indicate to the
// runtime to generate the state machine
result |= (System.Reflection.MethodImplAttributes)0x2000;
}
AddAsyncImplAttributeIfNeeded(ref result);

return result;
}
}

protected void AddAsyncImplAttributeIfNeeded(ref System.Reflection.MethodImplAttributes result)
{
if (this.IsAsync && this.DeclaringCompilation.IsRuntimeAsyncEnabledIn(this))
{
// When a method is emitted using runtime async, we add MethodImplAttributes.Async to indicate to the
// runtime to generate the state machine
result |= System.Reflection.MethodImplAttributes.Async;
}
}

internal override int TryGetOverloadResolutionPriority()
=> GetEarlyDecodedWellKnownAttributeData()?.OverloadResolutionPriority ?? 0;
}
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7 changes: 6 additions & 1 deletion ...Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedSimpleProgramEntryPointSymbol.cs
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Expand Up @@ -125,7 +125,12 @@ public override string Name

internal override System.Reflection.MethodImplAttributes ImplementationAttributes
{
get { return default(System.Reflection.MethodImplAttributes); }
get
{
var attributes = default(System.Reflection.MethodImplAttributes);
AddAsyncImplAttributeIfNeeded(ref attributes);
return attributes;
}
}

public override ImmutableArray<TypeParameterSymbol> TypeParameters
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23 changes: 10 additions & 13 deletions src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncTests.cs
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Expand Up @@ -23,9 +23,6 @@ namespace Microsoft.CodeAnalysis.CSharp.UnitTests.CodeGen
[CompilerTrait(CompilerFeature.Async)]
public class CodeGenAsyncTests : EmitMetadataTestBase
{
// https://github.com/dotnet/roslyn/issues/79792: Use the real value when possible
private const MethodImplAttributes MethodImplOptionsAsync = (MethodImplAttributes)0x2000;

internal static string ExpectedOutput(string output, bool isRuntimeAsync = false)
{
return ExecutionConditionUtil.IsMonoOrCoreClr
Expand Down Expand Up @@ -332,7 +329,7 @@ void verify(ModuleSymbol module)
{
var test = module.ContainingAssembly.GetTypeByMetadataName("Test");
var f = test.GetMethod("F");
Assert.Equal(MethodImplOptionsAsync, f.ImplementationAttributes);
Assert.Equal(MethodImplAttributes.Async, f.ImplementationAttributes);
AssertEx.Equal(["<>c"], test.GetTypeMembers().SelectAsArray(t => t.Name));
}
}
Expand Down Expand Up @@ -396,7 +393,7 @@ void verify(ModuleSymbol module)
{
var test = module.ContainingAssembly.GetTypeByMetadataName("Test");
var f = test.GetMethod("F");
Assert.Equal(MethodImplOptionsAsync, f.ImplementationAttributes);
Assert.Equal(MethodImplAttributes.Async, f.ImplementationAttributes);
Assert.Empty(test.GetTypeMembers());
}
}
Expand Down Expand Up @@ -459,7 +456,7 @@ void verify(ModuleSymbol module)
{
var test = module.ContainingAssembly.GetTypeByMetadataName("Test");
var f = test.GetMethod("F");
Assert.Equal(MethodImplOptionsAsync, f.ImplementationAttributes);
Assert.Equal(MethodImplAttributes.Async, f.ImplementationAttributes);
AssertEx.Equal(["<>c"], test.GetTypeMembers().SelectAsArray(t => t.Name));
}
}
Expand Down Expand Up @@ -512,7 +509,7 @@ void verify(ModuleSymbol module)
{
var test = module.ContainingAssembly.GetTypeByMetadataName("Test");
var f = test.GetMethod("F");
Assert.Equal(MethodImplOptionsAsync, f.ImplementationAttributes);
Assert.Equal(MethodImplAttributes.Async, f.ImplementationAttributes);
AssertEx.Empty(test.GetTypeMembers());
}
}
Expand Down Expand Up @@ -632,7 +629,7 @@ void verify(ModuleSymbol module)
{
var test = module.ContainingAssembly.GetTypeByMetadataName("Test");
var f = test.GetMethod("F");
Assert.Equal(MethodImplOptionsAsync, f.ImplementationAttributes);
Assert.Equal(MethodImplAttributes.Async, f.ImplementationAttributes);
if (!useValueTask && useGeneric)
{
AssertEx.Equal(["<>c"], test.GetTypeMembers().SelectAsArray(t => t.Name));
Expand Down Expand Up @@ -767,7 +764,7 @@ void verify(ModuleSymbol module)
{
var test = module.ContainingAssembly.GetTypeByMetadataName("Test");
var f = test.GetMethod("F");
Assert.Equal(MethodImplOptionsAsync, f.ImplementationAttributes);
Assert.Equal(MethodImplAttributes.Async, f.ImplementationAttributes);
AssertEx.Empty(test.GetTypeMembers());
}
}
Expand Down Expand Up @@ -887,7 +884,7 @@ void verify(ModuleSymbol module)
{
var test = module.ContainingAssembly.GetTypeByMetadataName("Test");
var f = test.GetMethod("F");
Assert.Equal(MethodImplOptionsAsync, f.ImplementationAttributes);
Assert.Equal(MethodImplAttributes.Async, f.ImplementationAttributes);
AssertEx.Empty(test.GetTypeMembers());
}
}
Expand Down Expand Up @@ -1019,7 +1016,7 @@ void verify(ModuleSymbol module)
{
var test = module.ContainingAssembly.GetTypeByMetadataName("Test");
var f = test.GetMethod("F");
Assert.Equal(MethodImplOptionsAsync, f.ImplementationAttributes);
Assert.Equal(MethodImplAttributes.Async, f.ImplementationAttributes);
AssertEx.Empty(test.GetTypeMembers());
}
}
Expand Down Expand Up @@ -1130,7 +1127,7 @@ void verify(ModuleSymbol module)
{
var test = module.ContainingAssembly.GetTypeByMetadataName("Test");
var f = test.GetMethod("F");
Assert.Equal(MethodImplOptionsAsync, f.ImplementationAttributes);
Assert.Equal(MethodImplAttributes.Async, f.ImplementationAttributes);
AssertEx.Empty(test.GetTypeMembers());
}
}
Expand Down Expand Up @@ -1238,7 +1235,7 @@ void verify(ModuleSymbol module)
{
var test = module.ContainingAssembly.GetTypeByMetadataName("Test");
var f = test.GetMethod("F");
Assert.Equal(MethodImplOptionsAsync, f.ImplementationAttributes);
Assert.Equal(MethodImplAttributes.Async, f.ImplementationAttributes);
AssertEx.Empty(test.GetTypeMembers());
}
}
Expand Down
93 changes: 91 additions & 2 deletions src/Compilers/CSharp/Test/Semantic/Semantics/TopLevelStatementsTests.cs
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Expand Up @@ -1104,7 +1104,7 @@ public void LocalDeclarationStatement_17()
CompileAndVerify(comp, expectedOutput: "Hi!");
}

[Fact]
[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/80313")]
public void LocalDeclarationStatement_18()
{
var text = @"
Expand Down Expand Up @@ -1133,6 +1133,50 @@ public void LocalDeclarationStatement_18()

comp = CreateCompilation(text, options: TestOptions.DebugExe);
comp.VerifyEmitDiagnostics();

comp = CreateRuntimeAsyncCompilation(text);
// https://github.com/dotnet/roslyn/issues/79791: Verify runtime async output
var verifier = CompileAndVerify(comp, expectedOutput: null, verify: Verification.Fails with
{
ILVerifyMessage = "[<Main>$]: Return value missing on the stack. { Offset = 0x2f }"
}, sourceSymbolValidator: validator);
verifier.VerifyIL("<top-level-statements-entry-point>", """
{
// Code size 48 (0x30)
.maxstack 1
.locals init (int V_0, //c
System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter V_1,
System.Runtime.CompilerServices.YieldAwaitable V_2)
IL_0000: ldc.i4.s -100
IL_0002: stloc.0
IL_0003: ldloca.s V_0
IL_0005: ldind.i4
IL_0006: call "void System.Console.Write(int)"
IL_000b: call "System.Runtime.CompilerServices.YieldAwaitable System.Threading.Tasks.Task.Yield()"
IL_0010: stloc.2
IL_0011: ldloca.s V_2
IL_0013: call "System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter System.Runtime.CompilerServices.YieldAwaitable.GetAwaiter()"
IL_0018: stloc.1
IL_0019: ldloca.s V_1
IL_001b: call "bool System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.IsCompleted.get"
IL_0020: brtrue.s IL_0028
IL_0022: ldloc.1
IL_0023: call "void System.Runtime.CompilerServices.AsyncHelpers.UnsafeAwaitAwaiter<System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter>(System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter)"
IL_0028: ldloca.s V_1
IL_002a: call "void System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.GetResult()"
IL_002f: ret
}
""");

static void validator(ModuleSymbol module)
{
var program = module.GlobalNamespace.GetTypeMember("Program");
Assert.NotNull(program);

var main = program.GetMethod("<Main>$");
Assert.NotNull(main);
Assert.Equal(MethodImplAttributes.Async, main.ImplementationAttributes & MethodImplAttributes.Async);
}
}

[Fact]
Expand Down Expand Up @@ -7825,7 +7869,7 @@ public void Return_03()
}
}

[Fact]
[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/80313")]
public void Return_04()
{
var text = @"
Expand Down Expand Up @@ -7893,6 +7937,51 @@ public void Return_04()
</methods>
</symbols>", options: PdbValidationOptions.SkipConversionValidation);
}

comp = CreateRuntimeAsyncCompilation(text);
// https://github.com/dotnet/roslyn/issues/79791: Verify runtime async output
var verifier = CompileAndVerify(comp, expectedOutput: null, verify: Verification.Fails with
{
ILVerifyMessage = "[<Main>$]: Unexpected type on the stack. { Offset = 0x43, Found = Int32, Expected = ref '[System.Runtime]System.Threading.Tasks.Task`1<int32>' }"
}, sourceSymbolValidator: validator);

verifier.VerifyIL("<top-level-statements-entry-point>", """
{
// Code size 68 (0x44)
.maxstack 3
IL_0000: ldstr "hello "
IL_0005: call "void System.Console.Write(string)"
IL_000a: call "System.Threading.Tasks.TaskFactory System.Threading.Tasks.Task.Factory.get"
IL_000f: ldsfld "System.Func<int> Program.<>c.<>9__0_0"
IL_0014: dup
IL_0015: brtrue.s IL_002e
IL_0017: pop
IL_0018: ldsfld "Program.<>c Program.<>c.<>9"
IL_001d: ldftn "int Program.<>c.<<Main>$>b__0_0()"
IL_0023: newobj "System.Func<int>..ctor(object, System.IntPtr)"
IL_0028: dup
IL_0029: stsfld "System.Func<int> Program.<>c.<>9__0_0"
IL_002e: callvirt "System.Threading.Tasks.Task<int> System.Threading.Tasks.TaskFactory.StartNew<int>(System.Func<int>)"
IL_0033: call "int System.Runtime.CompilerServices.AsyncHelpers.Await<int>(System.Threading.Tasks.Task<int>)"
IL_0038: pop
IL_0039: ldarg.0
IL_003a: ldc.i4.0
IL_003b: ldelem.ref
IL_003c: call "void System.Console.Write(string)"
IL_0041: ldc.i4.s 11
IL_0043: ret
}
""");

static void validator(ModuleSymbol module)
{
var program = module.GlobalNamespace.GetTypeMember("Program");
Assert.NotNull(program);

var main = program.GetMethod("<Main>$");
Assert.NotNull(main);
Assert.Equal(MethodImplAttributes.Async, main.ImplementationAttributes & MethodImplAttributes.Async);
}
}

[Fact]
Expand Down
26 changes: 26 additions & 0 deletions src/Compilers/Core/Portable/MethodImplExtensions.cs
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@@ -0,0 +1,26 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.Reflection;
using System.Runtime.CompilerServices;

namespace Microsoft.CodeAnalysis;

internal static class MethodImplAttributeExtensions
{
extension(MethodImplAttributes)
{
// https://github.com/dotnet/roslyn/issues/79792: Use the real value when possible
public static MethodImplAttributes Async => (MethodImplAttributes)0x2000;
}
}

internal static class MethodImplOptionsExtensions
{
extension(MethodImplOptions)
{
// https://github.com/dotnet/roslyn/issues/79792: Use the real value when possible
public static MethodImplOptions Async => (MethodImplOptions)0x2000;
}
}
6 changes: 2 additions & 4 deletions src/Compilers/Core/Portable/Symbols/Attributes/CommonAttributeData.cs
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Expand Up @@ -427,17 +427,15 @@ internal static void DecodeMethodImplAttribute<T, TAttributeSyntaxNode, TAttribu
options = options & ~(MethodImplOptions)3;
}

// https://github.com/dotnet/roslyn/issues/79792: Use the real value when possible
const MethodImplOptions MethodImplOptionsAsync = (MethodImplOptions)0x2000;
if ((options & MethodImplOptionsAsync) != 0)
if ((options & MethodImplOptions.Async) != 0)
{
// Error if [MethodImpl(MethodImplOptions.Async)] is used directly on a method
// We give an exception to the AsyncHelpers special type, as it manually implements the pattern as part of the
// runtime's async support
if ((InternalSpecialType)appliedToSymbol.ExtendedSpecialType != InternalSpecialType.System_Runtime_CompilerServices_AsyncHelpers)
{
arguments.Diagnostics.Add(messageProvider.CreateDiagnostic(messageProvider.ERR_MethodImplAttributeAsyncCannotBeUsed, arguments.AttributeSyntaxOpt.Location));
options &= ~MethodImplOptionsAsync;
options &= ~MethodImplOptions.Async;
}
}
}
Expand Down