80 lines
3.2 KiB
C#
80 lines
3.2 KiB
C#
/*
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Yarn Spinner is licensed to you under the terms found in the file LICENSE.md.
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*/
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using Microsoft.CodeAnalysis;
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using System.Linq;
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#nullable enable
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static class SymbolExtensions
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{
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/// <summary>
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/// If the <paramref name="symbol"/> is a method symbol, returns <see langword="true"/> if the method's return type is "awaitable", but not if it's <see langword="dynamic"/>.
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/// If the <paramref name="symbol"/> is a type symbol, returns <see langword="true"/> if that type is "awaitable".
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/// An "awaitable" is any type that exposes a GetAwaiter method which returns a valid "awaiter". This GetAwaiter method may be an instance method or an extension method.
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/// </summary>
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public static bool IsAwaitableNonDynamic(this ISymbol symbol, SemanticModel semanticModel, int position)
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{
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IMethodSymbol? methodSymbol = symbol as IMethodSymbol;
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ITypeSymbol? typeSymbol = null;
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if (methodSymbol == null)
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{
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typeSymbol = symbol as ITypeSymbol;
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if (typeSymbol == null)
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{
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return false;
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}
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}
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else
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{
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if (methodSymbol.ReturnType == null)
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{
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return false;
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}
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}
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// otherwise: needs valid GetAwaiter
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var potentialGetAwaiters = semanticModel.LookupSymbols(position,
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container: typeSymbol ?? methodSymbol?.ReturnType.OriginalDefinition,
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name: WellKnownMemberNames.GetAwaiter,
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includeReducedExtensionMethods: true);
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var getAwaiters = potentialGetAwaiters.OfType<IMethodSymbol>().Where(x => !x.Parameters.Any());
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return getAwaiters.Any(VerifyGetAwaiter);
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}
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private static bool VerifyGetAwaiter(IMethodSymbol getAwaiter)
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{
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var returnType = getAwaiter.ReturnType;
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if (returnType == null)
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{
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return false;
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}
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// bool IsCompleted { get }
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if (!returnType.GetMembers().OfType<IPropertySymbol>().Any(p => p.Name == WellKnownMemberNames.IsCompleted && p.Type.SpecialType == SpecialType.System_Boolean && p.GetMethod != null))
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{
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return false;
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}
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var methods = returnType.GetMembers().OfType<IMethodSymbol>();
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// NOTE: (vladres) The current version of C# Spec, §7.7.7.3 'Runtime evaluation of await expressions', requires that
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// NOTE: the interface method INotifyCompletion.OnCompleted or ICriticalNotifyCompletion.UnsafeOnCompleted is invoked
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// NOTE: (rather than any OnCompleted method conforming to a certain pattern).
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// NOTE: Should this code be updated to match the spec?
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// void OnCompleted(Action)
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// Actions are delegates, so we'll just check for delegates.
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if (!methods.Any(x => x.Name == WellKnownMemberNames.OnCompleted && x.ReturnsVoid && x.Parameters.Length == 1 && x.Parameters.First().Type.TypeKind == TypeKind.Delegate))
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{
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return false;
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}
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// void GetResult() || T GetResult()
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return methods.Any(m => m.Name == WellKnownMemberNames.GetResult && !m.Parameters.Any());
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}
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}
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