VSTHRD200 calculates all awaitable types, but only caches one

This block calculates all awaitable types, but only caches the one requested by an argument. This results in a large amount of recalculation.

vs-threading/src/Microsoft.VisualStudio.Threading.Analyzers/DiagnosticAnalyzerState.cs

Lines 42 to 49 in bcec580

    
           IEnumerable<ITypeSymbol>? awaitableTypesFromThisAssembly = from candidateAwaiterMethod in compilation.GetSymbolsWithName(m => m == GetAwaiterMethodName, SymbolFilter.Member, cancellationToken).OfType<IMethodSymbol>() 
        
                                                where candidateAwaiterMethod.IsExtensionMethod && !candidateAwaiterMethod.Parameters.IsEmpty 
        
                                                where ConformsToAwaiterPattern(candidateAwaiterMethod.ReturnType) 
        
                                                select candidateAwaiterMethod.Parameters[0].Type; 
        
           IEnumerable<ITypeSymbol>? awaitableTypesPerAssembly = from assembly in compilation.Assembly.Modules.First().ReferencedAssemblySymbols 
        
                                           from awaitableType in GetAwaitableTypes(assembly) 
        
                                           select awaitableType; 
        
           isAwaitable = awaitableTypesFromThisAssembly.Concat(awaitableTypesPerAssembly).Contains(typeSymbol);

Nice catch. That doesn't appear to find all awaitable types (it filters by candidateAwaiterMethod.IsExtensionMethod and not all awaitable types are by extensions method), but we should certainly cache all the data that we have computed.

It does filter by IsExtensionMethod, but perhaps it could specifically all known awaitable types created by extension methods? This would make it a true one-time calculation.

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VSTHRD200 calculates all awaitable types, but only caches one #829

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	IEnumerable<ITypeSymbol>? awaitableTypesFromThisAssembly = from candidateAwaiterMethod in compilation.GetSymbolsWithName(m => m == GetAwaiterMethodName, SymbolFilter.Member, cancellationToken).OfType<IMethodSymbol>()
	where candidateAwaiterMethod.IsExtensionMethod && !candidateAwaiterMethod.Parameters.IsEmpty
	where ConformsToAwaiterPattern(candidateAwaiterMethod.ReturnType)
	select candidateAwaiterMethod.Parameters[0].Type;
	IEnumerable<ITypeSymbol>? awaitableTypesPerAssembly = from assembly in compilation.Assembly.Modules.First().ReferencedAssemblySymbols
	from awaitableType in GetAwaitableTypes(assembly)
	select awaitableType;
	isAwaitable = awaitableTypesFromThisAssembly.Concat(awaitableTypesPerAssembly).Contains(typeSymbol);

VSTHRD200 calculates all awaitable types, but only caches one #829

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AArnott commented on Apr 20, 2021

sharwell commented on Apr 20, 2021

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