public static bool IsTypeAwaitable(Type type, out CoercedAwaitableInfo info)
{
if (AwaitableInfo.IsTypeAwaitable(type, out var directlyAwaitableInfo))
{
info = new CoercedAwaitableInfo(directlyAwaitableInfo);
return(true);
}
// It's not directly awaitable, but maybe we can coerce it.
// Currently we support coercing FSharpAsync<T>.
if (ObjectMethodExecutorFSharpSupport.TryBuildCoercerFromFSharpAsyncToAwaitable(type,
out var coercerExpression,
out var coercerResultType))
{
if (AwaitableInfo.IsTypeAwaitable(coercerResultType, out var coercedAwaitableInfo))
{
info = new CoercedAwaitableInfo(coercerExpression, coercerResultType, coercedAwaitableInfo);
return(true);
}
}
info = default(CoercedAwaitableInfo);
return(false);
}
public CoercedAwaitableInfo(AwaitableInfo awaitableInfo)
{
AwaitableInfo = awaitableInfo;
CoercerExpression = null;
CoercerResultType = null;
}
public CoercedAwaitableInfo(Expression coercerExpression, Type coercerResultType, AwaitableInfo coercedAwaitableInfo)
{
CoercerExpression = coercerExpression;
CoercerResultType = coercerResultType;
AwaitableInfo = coercedAwaitableInfo;
}
public static bool IsTypeAwaitable(Type type, out AwaitableInfo awaitableInfo)
{
// Based on Roslyn code: http://source.roslyn.io/#Microsoft.CodeAnalysis.Workspaces/Shared/Extensions/ISymbolExtensions.cs,db4d48ba694b9347
// Awaitable must have method matching "object GetAwaiter()"
var getAwaiterMethod = type.GetRuntimeMethods().FirstOrDefault(m =>
m.Name.Equals("GetAwaiter", StringComparison.OrdinalIgnoreCase) &&
m.GetParameters().Length == 0 &&
m.ReturnType != null);
if (getAwaiterMethod == null)
{
awaitableInfo = default(AwaitableInfo);
return(false);
}
var awaiterType = getAwaiterMethod.ReturnType;
// Awaiter must have property matching "bool IsCompleted { get; }"
var isCompletedProperty = awaiterType.GetRuntimeProperties().FirstOrDefault(p =>
p.Name.Equals("IsCompleted", StringComparison.OrdinalIgnoreCase) &&
p.PropertyType == typeof(bool) &&
p.GetMethod != null);
if (isCompletedProperty == null)
{
awaitableInfo = default(AwaitableInfo);
return(false);
}
// Awaiter must implement INotifyCompletion
var awaiterInterfaces = awaiterType.GetInterfaces();
var implementsINotifyCompletion = awaiterInterfaces.Any(t => t == typeof(INotifyCompletion));
if (!implementsINotifyCompletion)
{
awaitableInfo = default(AwaitableInfo);
return(false);
}
// INotifyCompletion supplies a method matching "void OnCompleted(Action action)"
var iNotifyCompletionMap = awaiterType
.GetTypeInfo()
.GetRuntimeInterfaceMap(typeof(INotifyCompletion));
var onCompletedMethod = iNotifyCompletionMap.InterfaceMethods.Single(m =>
m.Name.Equals("OnCompleted", StringComparison.OrdinalIgnoreCase) &&
m.ReturnType == typeof(void) &&
m.GetParameters().Length == 1 &&
m.GetParameters()[0].ParameterType == typeof(Action));
// Awaiter optionally implements ICriticalNotifyCompletion
var implementsICriticalNotifyCompletion = awaiterInterfaces.Any(t => t == typeof(ICriticalNotifyCompletion));
MethodInfo unsafeOnCompletedMethod;
if (implementsICriticalNotifyCompletion)
{
// ICriticalNotifyCompletion supplies a method matching "void UnsafeOnCompleted(Action action)"
var iCriticalNotifyCompletionMap = awaiterType
.GetTypeInfo()
.GetRuntimeInterfaceMap(typeof(ICriticalNotifyCompletion));
unsafeOnCompletedMethod = iCriticalNotifyCompletionMap.InterfaceMethods.Single(m =>
m.Name.Equals("UnsafeOnCompleted", StringComparison.OrdinalIgnoreCase) &&
m.ReturnType == typeof(void) &&
m.GetParameters().Length == 1 &&
m.GetParameters()[0].ParameterType == typeof(Action));
}
else
{
unsafeOnCompletedMethod = null;
}
// Awaiter must have method matching "void GetResult" or "T GetResult()"
var getResultMethod = awaiterType.GetRuntimeMethods().FirstOrDefault(m =>
m.Name.Equals("GetResult") &&
m.GetParameters().Length == 0);
if (getResultMethod == null)
{
awaitableInfo = default(AwaitableInfo);
return(false);
}
awaitableInfo = new AwaitableInfo(
awaiterType,
isCompletedProperty,
getResultMethod,
onCompletedMethod,
unsafeOnCompletedMethod,
getResultMethod.ReturnType,
getAwaiterMethod);
return(true);
}