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// 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.Collections.Generic;
using System.Collections.Immutable;
using System.Diagnostics;
using Microsoft.CodeAnalysis.CodeGen;
using Microsoft.CodeAnalysis.CSharp.Symbols;
using Microsoft.CodeAnalysis.Emit;
using Microsoft.CodeAnalysis.PooledObjects;
namespace Microsoft.CodeAnalysis.CSharp
{
internal partial class AsyncRewriter : StateMachineRewriter
{
private readonly AsyncMethodBuilderMemberCollection _asyncMethodBuilderMemberCollection;
private readonly bool _constructedSuccessfully;
private readonly int _methodOrdinal;
private FieldSymbol? _builderField;
private AsyncRewriter(
BoundStatement body,
MethodSymbol method,
int methodOrdinal,
AsyncStateMachine stateMachineType,
ArrayBuilder<StateMachineStateDebugInfo> stateMachineStateDebugInfoBuilder,
VariableSlotAllocator? slotAllocatorOpt,
TypeCompilationState compilationState,
BindingDiagnosticBag diagnostics)
: base(body, method, stateMachineType, stateMachineStateDebugInfoBuilder, slotAllocatorOpt, compilationState, diagnostics)
{
_constructedSuccessfully = AsyncMethodBuilderMemberCollection.TryCreate(F, method, this.stateMachineType.TypeMap, out _asyncMethodBuilderMemberCollection);
_methodOrdinal = methodOrdinal;
}
/// <summary>
/// Rewrite an async method into a state machine type.
/// </summary>
internal static BoundStatement Rewrite(
BoundStatement bodyWithAwaitLifted,
MethodSymbol method,
int methodOrdinal,
ArrayBuilder<StateMachineStateDebugInfo> stateMachineStateDebugInfoBuilder,
VariableSlotAllocator? slotAllocatorOpt,
TypeCompilationState compilationState,
BindingDiagnosticBag diagnostics,
out AsyncStateMachine? stateMachineType)
{
Debug.Assert(compilationState.ModuleBuilderOpt != null);
if (!method.IsAsync)
{
stateMachineType = null;
return bodyWithAwaitLifted;
}
CSharpCompilation compilation = method.DeclaringCompilation;
bool isAsyncEnumerableOrEnumerator = method.IsAsyncReturningIAsyncEnumerable(compilation) ||
method.IsAsyncReturningIAsyncEnumerator(compilation);
if (isAsyncEnumerableOrEnumerator && !method.IsIterator)
{
bool containsAwait = AwaitDetector.ContainsAwait(bodyWithAwaitLifted);
diagnostics.Add(containsAwait ? ErrorCode.ERR_PossibleAsyncIteratorWithoutYield : ErrorCode.ERR_PossibleAsyncIteratorWithoutYieldOrAwait,
method.GetFirstLocation());
stateMachineType = null;
return bodyWithAwaitLifted;
}
// The CLR doesn't support adding fields to structs, so in order to enable EnC in an async method we need to generate a class.
// For async-iterators, we also need to generate a class.
var typeKind = (compilationState.Compilation.Options.EnableEditAndContinue || method.IsIterator) ? TypeKind.Class : TypeKind.Struct;
stateMachineType = new AsyncStateMachine(slotAllocatorOpt, compilationState, method, methodOrdinal, typeKind);
compilationState.ModuleBuilderOpt.CompilationState.SetStateMachineType(method, stateMachineType);
AsyncRewriter rewriter = isAsyncEnumerableOrEnumerator
? new AsyncIteratorRewriter(bodyWithAwaitLifted, method, methodOrdinal, stateMachineType, stateMachineStateDebugInfoBuilder, slotAllocatorOpt, compilationState, diagnostics)
: new AsyncRewriter(bodyWithAwaitLifted, method, methodOrdinal, stateMachineType, stateMachineStateDebugInfoBuilder, slotAllocatorOpt, compilationState, diagnostics);
if (!rewriter.VerifyPresenceOfRequiredAPIs())
{
return bodyWithAwaitLifted;
}
try
{
return rewriter.Rewrite();
}
catch (SyntheticBoundNodeFactory.MissingPredefinedMember ex)
{
diagnostics.Add(ex.Diagnostic);
return new BoundBadStatement(bodyWithAwaitLifted.Syntax, ImmutableArray.Create<BoundNode>(bodyWithAwaitLifted), hasErrors: true);
}
}
#nullable disable
/// <returns>
/// Returns true if all types and members we need are present and good
/// </returns>
protected bool VerifyPresenceOfRequiredAPIs()
{
var bag = BindingDiagnosticBag.GetInstance(withDiagnostics: true, diagnostics.AccumulatesDependencies);
VerifyPresenceOfRequiredAPIs(bag);
bool hasErrors = bag.HasAnyErrors();
if (!hasErrors)
{
diagnostics.AddDependencies(bag);
}
else
{
diagnostics.AddRange(bag);
}
bag.Free();
return !hasErrors && _constructedSuccessfully;
}
protected virtual void VerifyPresenceOfRequiredAPIs(BindingDiagnosticBag bag)
{
EnsureWellKnownMember(WellKnownMember.System_Runtime_CompilerServices_IAsyncStateMachine_MoveNext, bag);
EnsureWellKnownMember(WellKnownMember.System_Runtime_CompilerServices_IAsyncStateMachine_SetStateMachine, bag);
}
private Symbol EnsureWellKnownMember(WellKnownMember member, BindingDiagnosticBag bag)
{
return Binder.GetWellKnownTypeMember(F.Compilation, member, bag, body.Syntax.Location);
}
protected override bool PreserveInitialParameterValuesAndThreadId
=> false;
protected override void GenerateControlFields()
{
// the fields are initialized from async method, so they need to be public:
stateField = F.StateMachineField(F.SpecialType(SpecialType.System_Int32), GeneratedNames.MakeStateMachineStateFieldName(), isPublic: true);
_builderField = F.StateMachineField(_asyncMethodBuilderMemberCollection.BuilderType, GeneratedNames.AsyncBuilderFieldName(), isPublic: true);
var instrumentations = F.ModuleBuilderOpt.GetMethodBodyInstrumentations(method);
if (instrumentations.Kinds.Contains(InstrumentationKindExtensions.LocalStateTracing))
{
instanceIdField = F.StateMachineField(F.SpecialType(SpecialType.System_UInt64), GeneratedNames.MakeStateMachineStateIdFieldName(), isPublic: true);
}
}
protected override void GenerateMethodImplementations()
{
var IAsyncStateMachine_MoveNext = F.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_IAsyncStateMachine_MoveNext);
var IAsyncStateMachine_SetStateMachine = F.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_IAsyncStateMachine_SetStateMachine);
// Add IAsyncStateMachine.MoveNext()
var moveNextMethod = OpenMoveNextMethodImplementation(IAsyncStateMachine_MoveNext);
GenerateMoveNext(moveNextMethod);
// Add IAsyncStateMachine.SetStateMachine()
OpenMethodImplementation(
IAsyncStateMachine_SetStateMachine,
"SetStateMachine",
hasMethodBodyDependency: false);
// SetStateMachine is used to initialize the underlying AsyncMethodBuilder's reference to the boxed copy of the state machine.
// If the state machine is a class there is no copy made and thus the initialization is not necessary.
// In fact it is an error to reinitialize the builder since it already is initialized.
if (F.CurrentType.TypeKind == TypeKind.Class)
{
F.CloseMethod(F.Return());
}
else
{
F.CloseMethod(
// this.builderField.SetStateMachine(sm)
F.Block(
F.ExpressionStatement(
F.Call(
F.Field(F.This(), _builderField),
_asyncMethodBuilderMemberCollection.SetStateMachine,
new BoundExpression[] { F.Parameter(F.CurrentFunction.Parameters[0]) })),
F.Return()));
}
// Constructor
GenerateConstructor();
}
protected virtual void GenerateConstructor()
{
if (stateMachineType.TypeKind == TypeKind.Class)
{
F.CurrentFunction = stateMachineType.Constructor;
F.CloseMethod(F.Block(ImmutableArray.Create(F.BaseInitialization(), F.Return())));
}
}
protected override void InitializeStateMachine(ArrayBuilder<BoundStatement> bodyBuilder, NamedTypeSymbol frameType, LocalSymbol stateMachineLocal)
{
if (frameType.TypeKind == TypeKind.Class)
{
// local = new {state machine type}();
bodyBuilder.Add(
F.Assignment(
F.Local(stateMachineLocal),
F.New(frameType.InstanceConstructors[0])));
}
}
protected override BoundStatement GenerateStateMachineCreation(LocalSymbol stateMachineVariable, NamedTypeSymbol frameType, IReadOnlyDictionary<Symbol, CapturedSymbolReplacement> proxies)
{
// If the async method's result type is a type parameter of the method, then the AsyncTaskMethodBuilder<T>
// needs to use the method's type parameters inside the rewritten method body. All other methods generated
// during async rewriting are members of the synthesized state machine struct, and use the type parameters
// structs type parameters.
AsyncMethodBuilderMemberCollection methodScopeAsyncMethodBuilderMemberCollection;
if (!AsyncMethodBuilderMemberCollection.TryCreate(F, method, null, out methodScopeAsyncMethodBuilderMemberCollection))
{
return new BoundBadStatement(F.Syntax, ImmutableArray<BoundNode>.Empty, hasErrors: true);
}
var bodyBuilder = ArrayBuilder<BoundStatement>.GetInstance();
// local.$builder = System.Runtime.CompilerServices.AsyncTaskMethodBuilder<typeArgs>.Create();
bodyBuilder.Add(
F.Assignment(
F.Field(F.Local(stateMachineVariable), _builderField.AsMember(frameType)),
F.StaticCall(
null,
methodScopeAsyncMethodBuilderMemberCollection.CreateBuilder)));
bodyBuilder.Add(GenerateParameterStorage(stateMachineVariable, proxies));
// local.$stateField = NotStartedStateMachine
bodyBuilder.Add(
F.Assignment(
F.Field(F.Local(stateMachineVariable), stateField.AsMember(frameType)),
F.Literal(StateMachineState.NotStartedOrRunningState)));
// local.$instanceIdField = LocalStoreTracker.GetNewStateMachineInstanceId()
if (instanceIdField is not null &&
F.WellKnownMethod(WellKnownMember.Microsoft_CodeAnalysis_Runtime_LocalStoreTracker__GetNewStateMachineInstanceId) is { } getId)
{
bodyBuilder.Add(
F.Assignment(
F.Field(F.Local(stateMachineVariable), instanceIdField.AsMember(frameType)),
F.Call(receiver: null, getId)));
}
// local.$builder.Start(ref local) -- binding to the method AsyncTaskMethodBuilder<typeArgs>.Start()
var startMethod = methodScopeAsyncMethodBuilderMemberCollection.Start.Construct(frameType);
if (methodScopeAsyncMethodBuilderMemberCollection.CheckGenericMethodConstraints)
{
startMethod.CheckConstraints(new ConstraintsHelper.CheckConstraintsArgs(F.Compilation, F.Compilation.Conversions, includeNullability: false, F.Syntax.Location, diagnostics));
}
bodyBuilder.Add(
F.ExpressionStatement(
F.Call(
F.Field(F.Local(stateMachineVariable), _builderField.AsMember(frameType)),
startMethod,
ImmutableArray.Create<BoundExpression>(F.Local(stateMachineVariable)))));
bodyBuilder.Add(method.IsAsyncReturningVoid()
? F.Return()
: F.Return(
F.Property(
F.Field(F.Local(stateMachineVariable), _builderField.AsMember(frameType)),
methodScopeAsyncMethodBuilderMemberCollection.Task)));
return F.Block(bodyBuilder.ToImmutableAndFree());
}
protected virtual void GenerateMoveNext(SynthesizedImplementationMethod moveNextMethod)
{
var rewriter = new AsyncMethodToStateMachineRewriter(
method: method,
methodOrdinal: _methodOrdinal,
asyncMethodBuilderMemberCollection: _asyncMethodBuilderMemberCollection,
F: F,
state: stateField,
builder: _builderField,
instanceIdField: instanceIdField,
hoistedVariables: hoistedVariables,
nonReusableLocalProxies: nonReusableLocalProxies,
synthesizedLocalOrdinals: synthesizedLocalOrdinals,
stateMachineStateDebugInfoBuilder,
slotAllocatorOpt: slotAllocatorOpt,
nextFreeHoistedLocalSlot: nextFreeHoistedLocalSlot,
diagnostics: diagnostics);
rewriter.GenerateMoveNext(body, moveNextMethod);
}
/// <summary>
/// Note: do not use a static/singleton instance of this type, as it holds state.
/// </summary>
private class AwaitDetector : BoundTreeWalkerWithStackGuardWithoutRecursionOnTheLeftOfBinaryOperator
{
private bool _sawAwait;
public static bool ContainsAwait(BoundNode node)
{
var detector = new AwaitDetector();
detector.Visit(node);
return detector._sawAwait;
}
public override BoundNode VisitAwaitExpression(BoundAwaitExpression node)
{
_sawAwait = true;
return null;
}
}
}
}
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