//
// Return container with awaiter definition. It never returns null
// but all container member can be null for easier error reporting
//
public AwaiterDefinition GetAwaiter(TypeSpec type)
{
AwaiterDefinition awaiter;
if (awaiters.TryGetValue(type, out awaiter))
{
return(awaiter);
}
awaiter = new AwaiterDefinition();
//
// Predefined: bool IsCompleted { get; }
//
awaiter.IsCompleted = MemberCache.FindMember(type, MemberFilter.Property("IsCompleted", Compiler.BuiltinTypes.Bool),
BindingRestriction.InstanceOnly) as PropertySpec;
//
// Predefined: GetResult ()
//
// The method return type is also result type of await expression
//
awaiter.GetResult = MemberCache.FindMember(type, MemberFilter.Method("GetResult", 0,
ParametersCompiled.EmptyReadOnlyParameters, null),
BindingRestriction.InstanceOnly) as MethodSpec;
//
// Predefined: INotifyCompletion.OnCompleted (System.Action)
//
var nc = PredefinedTypes.INotifyCompletion;
awaiter.INotifyCompletion = !nc.Define() || type.ImplementsInterface(nc.TypeSpec, false);
awaiters.Add(type, awaiter);
return(awaiter);
}
public override bool Resolve(BlockContext bc)
{
if (bc.CurrentBlock is Linq.QueryBlock)
{
bc.Report.Error(1995, loc,
"The `await' operator may only be used in a query expression within the first collection expression of the initial `from' clause or within the collection expression of a `join' clause");
return(false);
}
if (!base.Resolve(bc))
{
return(false);
}
type = expr.Type;
Arguments args = new Arguments(0);
//
// The await expression is of dynamic type
//
if (type.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
{
result_type = type;
expr = new Invocation(new MemberAccess(expr, "GetAwaiter"), args).Resolve(bc);
return(true);
}
//
// Check whether the expression is awaitable
//
Expression ama = new AwaitableMemberAccess(expr).Resolve(bc);
if (ama == null)
{
return(false);
}
var errors_printer = new SessionReportPrinter();
var old = bc.Report.SetPrinter(errors_printer);
ama = new Invocation(ama, args).Resolve(bc);
bc.Report.SetPrinter(old);
if (errors_printer.ErrorsCount > 0 || !MemberAccess.IsValidDotExpression(ama.Type))
{
bc.Report.Error(1986, expr.Location,
"The `await' operand type `{0}' must have suitable GetAwaiter method",
expr.Type.GetSignatureForError());
return(false);
}
var awaiter_type = ama.Type;
awaiter_definition = bc.Module.GetAwaiter(awaiter_type);
if (!awaiter_definition.IsValidPattern)
{
Error_WrongAwaiterPattern(bc, awaiter_type);
return(false);
}
if (!awaiter_definition.INotifyCompletion)
{
bc.Report.Error(4027, loc, "The awaiter type `{0}' must implement interface `{1}'",
awaiter_type.GetSignatureForError(), bc.Module.PredefinedTypes.INotifyCompletion.GetSignatureForError());
return(false);
}
expr = ama;
result_type = awaiter_definition.GetResult.ReturnType;
return(true);
}