public override Expression/*!*/ Convert(DynamicMetaObject/*!*/ metaObject, Type restrictedType, ParameterInfo info, Type/*!*/ toType) {
Expression expr = metaObject.Expression;
Type fromType = restrictedType ?? expr.Type;
// block:
if (fromType == typeof(MissingBlockParam)) {
Debug.Assert(toType == typeof(BlockParam) || toType == typeof(MissingBlockParam));
return AstUtils.Constant(null);
}
if (fromType == typeof(BlockParam) && toType == typeof(MissingBlockParam)) {
return AstUtils.Constant(null);
}
// protocol conversions:
if (info != null && info.IsAttributeDefined(typeof(DefaultProtocolAttribute), false)) {
var action = RubyConversionAction.TryGetDefaultConversionAction(Context, toType);
if (action != null) {
// TODO: inline implicit conversions:
return Ast.Dynamic(action, toType, expr);
}
// Do not throw an exception here to allow generic type parameters to be used with D.P. attribute.
// The semantics should be to use DP if available for the current instantiation and ignore it otherwise.
}
if (restrictedType != null) {
if (restrictedType == typeof(DynamicNull)) {
if (!toType.IsValueType || toType.IsGenericType && toType.GetGenericTypeDefinition() == typeof(Nullable<>)) {
return AstUtils.Constant(null, toType);
} else if (toType == typeof(bool)) {
return AstUtils.Constant(false);
}
}
if (toType.IsAssignableFrom(restrictedType)) {
// expr can be converted to restrictedType, which can be converted toType => we can convert expr to toType:
return AstUtils.Convert(expr, CompilerHelpers.GetVisibleType(toType));
}
// if there is a simple conversion from restricted type, convert the expression to the restricted type and use that conversion:
Type visibleRestrictedType = CompilerHelpers.GetVisibleType(restrictedType);
if (Converter.CanConvertFrom(metaObject, visibleRestrictedType, toType, false, NarrowingLevel.None, false, false)) {
expr = AstUtils.Convert(expr, visibleRestrictedType);
}
}
return Converter.ConvertExpression(expr, toType, _args.RubyContext, _args.MetaContext.Expression, _implicitProtocolConversions);
}
public static bool IsParamDictionary(ParameterInfo parameter) {
return parameter.IsAttributeDefined(typeof(ParamDictionaryAttribute), false);
}