public static MetaProjectorExpression AsProjection(Expression expression)
{
if (expression is MetaProjectorExpression mpe)
{
return(mpe);
}
if (expression.NodeType == ExpressionType.New)
{
NewExpression nex = (NewExpression)expression;
if (nex.Type.IsInstantiationOf(typeof(Grouping <,>)))
{
return((MetaProjectorExpression)nex.Arguments[1]);
}
}
Type?elementType = expression.Type.ElementType();
if (elementType != null)
{
if (expression is MetaExpression meta && meta.Meta is CleanMeta)
{
PropertyRoute route = ((CleanMeta)meta.Meta).PropertyRoutes.SingleEx(() => "PropertyRoutes for {0}. Metas don't work over polymorphic MLists".FormatWith(meta.Meta)).Add("Item");
return(new MetaProjectorExpression(expression.Type,
new MetaExpression(elementType,
new CleanMeta(route.TryGetImplementations(), route))));
}
return(new MetaProjectorExpression(expression.Type, MakeVoidMeta(elementType)));
}
throw new InvalidOperationException();
}
protected override Expression VisitConstant(ConstantExpression c)
{
Type type = TableType(c.Value);
if (type != null)
{
if (typeof(Entity).IsAssignableFrom(type))
{
return(new MetaProjectorExpression(c.Type, new MetaExpression(type, new CleanMeta(Implementations.By(type), PropertyRoute.Root(type)))));
}
if (type.IsInstantiationOf(typeof(MListElement <,>)))
{
var parentType = type.GetGenericArguments()[0];
ISignumTable st = (ISignumTable)c.Value;
TableMList rt = (TableMList)st.Table;
PropertyRoute element = rt.PropertyRoute.Add("Item");
return(new MetaProjectorExpression(c.Type, new MetaMListExpression(type,
new CleanMeta(Implementations.By(parentType), PropertyRoute.Root(rt.PropertyRoute.RootType)),
new CleanMeta(element.TryGetImplementations(), element))));
}
}
return(MakeVoidMeta(c.Type));
}