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);
}