private static LambdaConversionResult IsAnonymousFunctionCompatibleWithExpressionTree(UnboundLambda anonymousFunction, NamedTypeSymbol type)
{
Debug.Assert((object)anonymousFunction != null);
Debug.Assert((object)type != null);
Debug.Assert(type.IsExpressionTree());
// SPEC OMISSION:
//
// The C# 3 spec said that anonymous methods and statement lambdas are *convertible* to expression tree
// types if the anonymous method/statement lambda is convertible to its delegate type; however, actually
// *using* such a conversion is an error. However, that is not what we implemented. In C# 3 we implemented
// that an anonymous method is *not convertible* to an expression tree type, period. (Statement lambdas
// used the rule described in the spec.)
//
// This appears to be a spec omission; the intention is to make old-style anonymous methods not
// convertible to expression trees.
var delegateType = type.TypeArgumentsNoUseSiteDiagnostics[0];
if (!delegateType.IsDelegateType())
{
return LambdaConversionResult.ExpressionTreeMustHaveDelegateTypeArgument;
}
if (anonymousFunction.Syntax.Kind == SyntaxKind.AnonymousMethodExpression)
{
return LambdaConversionResult.ExpressionTreeFromAnonymousMethod;
}
return IsAnonymousFunctionCompatibleWithDelegate(anonymousFunction, delegateType);
}
