C# MethodSymbol.IsTaskReturningAsync方法代码示例

        /// <summary>
        /// The flow analysis pass.  This pass reports required diagnostics for unreachable
        /// statements and uninitialized variables (through the call to FlowAnalysisWalker.Analyze),
        /// and inserts a final return statement if the end of a void-returning method is reachable.
        /// </summary>
        /// <param name="method">the method to be analyzed</param>
        /// <param name="block">the method's body</param>
        /// <param name="diagnostics">the receiver of the reported diagnostics</param>
        /// <param name="hasTrailingExpression">indicates whether this Script had a trailing expression</param>
        /// <param name="originalBodyNested">the original method body is the last statement in the block</param>
        /// <returns>the rewritten block for the method (with a return statement possibly inserted)</returns>
        public static BoundBlock Rewrite(
            MethodSymbol method,
            BoundBlock block,
            DiagnosticBag diagnostics,
            bool hasTrailingExpression,
            bool originalBodyNested)
        {
#if DEBUG
            // We should only see a trailingExpression if we're in a Script initializer.
            Debug.Assert(!hasTrailingExpression || method.IsScriptInitializer);
            var initialDiagnosticCount = diagnostics.ToReadOnly().Length;
#endif
            var compilation = method.DeclaringCompilation;

            if (method.ReturnsVoid || method.IsIterator || method.IsTaskReturningAsync(compilation))
            {
                // we don't analyze synthesized void methods.
                if ((method.IsImplicitlyDeclared && !method.IsScriptInitializer) || Analyze(compilation, method, block, diagnostics))
                {
                    block = AppendImplicitReturn(block, method, (CSharpSyntaxNode)(method as SourceMethodSymbol)?.BodySyntax, originalBodyNested);
                }
            }
            else if (Analyze(compilation, method, block, diagnostics))
            {
                // If the method is a lambda expression being converted to a non-void delegate type
                // and the end point is reachable then suppress the error here; a special error
                // will be reported by the lambda binder.
                Debug.Assert(method.MethodKind != MethodKind.AnonymousFunction);

                // Add implicit "return default(T)" if this is a submission that does not have a trailing expression.
                var submissionResultType = (method as SynthesizedInteractiveInitializerMethod)?.ResultType;
                if (!hasTrailingExpression && ((object)submissionResultType != null))
                {
                    Debug.Assert(submissionResultType.SpecialType != SpecialType.System_Void);

                    var trailingExpression = new BoundDefaultOperator(method.GetNonNullSyntaxNode(), submissionResultType);
                    var newStatements = block.Statements.Add(new BoundReturnStatement(trailingExpression.Syntax, RefKind.None, trailingExpression));
                    block = new BoundBlock(block.Syntax, ImmutableArray<LocalSymbol>.Empty, ImmutableArray<LocalFunctionSymbol>.Empty, newStatements) { WasCompilerGenerated = true };
#if DEBUG
                    // It should not be necessary to repeat analysis after adding this node, because adding a trailing
                    // return in cases where one was missing should never produce different Diagnostics.
                    var flowAnalysisDiagnostics = DiagnosticBag.GetInstance();
                    Debug.Assert(!Analyze(compilation, method, block, flowAnalysisDiagnostics));
                    Debug.Assert(flowAnalysisDiagnostics.ToReadOnly().SequenceEqual(diagnostics.ToReadOnly().Skip(initialDiagnosticCount)));
                    flowAnalysisDiagnostics.Free();
#endif
                }
                // If there's more than one location, then the method is partial and we
                // have already reported a non-void partial method error.
                else if (method.Locations.Length == 1)
                {
                    diagnostics.Add(ErrorCode.ERR_ReturnExpected, method.Locations[0], method);
                }
            }

            return block;
        }

 private bool ImplicitReturnIsOkay(MethodSymbol method)
 {
     return method.ReturnsVoid || method.IsIterator || method.IsTaskReturningAsync(this.Compilation);
 }

        internal static bool TryCreate(SyntheticBoundNodeFactory F, MethodSymbol method, TypeMap typeMap, out AsyncMethodBuilderMemberCollection collection)
        {
            if (method.IsVoidReturningAsync())
            {
                return TryCreate(
                    F: F,

                    builderType: F.WellKnownType(WellKnownType.System_Runtime_CompilerServices_AsyncVoidMethodBuilder),
                    resultType: F.SpecialType(SpecialType.System_Void),

                    setException: WellKnownMember.System_Runtime_CompilerServices_AsyncVoidMethodBuilder__SetException,
                    setResult: WellKnownMember.System_Runtime_CompilerServices_AsyncVoidMethodBuilder__SetResult,
                    awaitOnCompleted: WellKnownMember.System_Runtime_CompilerServices_AsyncVoidMethodBuilder__AwaitOnCompleted,
                    awaitUnsafeOnCompleted: WellKnownMember.System_Runtime_CompilerServices_AsyncVoidMethodBuilder__AwaitUnsafeOnCompleted,
                    start: WellKnownMember.System_Runtime_CompilerServices_AsyncVoidMethodBuilder__Start_T,
                    setStateMachine: WellKnownMember.System_Runtime_CompilerServices_AsyncVoidMethodBuilder__SetStateMachine,
                    task: null,
                    collection: out collection);
            }

            if (method.IsTaskReturningAsync(F.Compilation))
            {
                NamedTypeSymbol builderType = F.WellKnownType(WellKnownType.System_Runtime_CompilerServices_AsyncTaskMethodBuilder);

                PropertySymbol task;
                if (!TryGetWellKnownPropertyAsMember(F, WellKnownMember.System_Runtime_CompilerServices_AsyncTaskMethodBuilder__Task, builderType, out task))
                {
                    collection = default(AsyncMethodBuilderMemberCollection);
                    return false;
                }

                return TryCreate(
                    F: F,

                    builderType: F.WellKnownType(WellKnownType.System_Runtime_CompilerServices_AsyncTaskMethodBuilder),
                    resultType: F.SpecialType(SpecialType.System_Void),

                    setException: WellKnownMember.System_Runtime_CompilerServices_AsyncTaskMethodBuilder__SetException,
                    setResult: WellKnownMember.System_Runtime_CompilerServices_AsyncTaskMethodBuilder__SetResult,
                    awaitOnCompleted: WellKnownMember.System_Runtime_CompilerServices_AsyncTaskMethodBuilder__AwaitOnCompleted,
                    awaitUnsafeOnCompleted: WellKnownMember.System_Runtime_CompilerServices_AsyncTaskMethodBuilder__AwaitUnsafeOnCompleted,
                    start: WellKnownMember.System_Runtime_CompilerServices_AsyncTaskMethodBuilder__Start_T,
                    setStateMachine: WellKnownMember.System_Runtime_CompilerServices_AsyncTaskMethodBuilder__SetStateMachine,
                    task: task,
                    collection: out collection);
            }

            if (method.IsGenericTaskReturningAsync(F.Compilation))
            {
                TypeSymbol resultType = method.ReturnType.GetMemberTypeArgumentsNoUseSiteDiagnostics().Single();

                if (resultType.IsDynamic())
                {
                    resultType = F.SpecialType(SpecialType.System_Object);
                }

                if (typeMap != null)
                {
                    resultType = typeMap.SubstituteType(resultType).Type;
                }

                NamedTypeSymbol builderType = F.WellKnownType(WellKnownType.System_Runtime_CompilerServices_AsyncTaskMethodBuilder_T).Construct(resultType);

                PropertySymbol task;
                if (!TryGetWellKnownPropertyAsMember(F, WellKnownMember.System_Runtime_CompilerServices_AsyncTaskMethodBuilder_T__Task, builderType, out task))
                {
                    collection = default(AsyncMethodBuilderMemberCollection);
                    return false;
                }

                return TryCreate(
                    F: F,

                    builderType: builderType,
                    resultType: resultType,

                    setException: WellKnownMember.System_Runtime_CompilerServices_AsyncTaskMethodBuilder_T__SetException,
                    setResult: WellKnownMember.System_Runtime_CompilerServices_AsyncTaskMethodBuilder_T__SetResult,
                    awaitOnCompleted: WellKnownMember.System_Runtime_CompilerServices_AsyncTaskMethodBuilder_T__AwaitOnCompleted,
                    awaitUnsafeOnCompleted: WellKnownMember.System_Runtime_CompilerServices_AsyncTaskMethodBuilder_T__AwaitUnsafeOnCompleted,
                    start: WellKnownMember.System_Runtime_CompilerServices_AsyncTaskMethodBuilder_T__Start_T,
                    setStateMachine: WellKnownMember.System_Runtime_CompilerServices_AsyncTaskMethodBuilder_T__SetStateMachine,
                    task: task,
                    collection: out collection);
            }

            throw ExceptionUtilities.UnexpectedValue(method);
        }