Re: Indexer on generic argument

Pavel Minaev wrote:
On Aug 7, 6:47 pm, "Ben Voigt [C++ MVP]" <r...@xxxxxxxxxxxxx> wrote:
generic <typename TList, typename ItemType> where TList :
IList<ItemType>
ref class MyClass
{
public:
MyClass() {}
void Method(TList list1)
{
Console::Write("{0}, ", list1[0]); // error C2109 ??
IList<ItemType>^ list2 = list1;

This line shouldn't have worked -- list1 has stack semantics
(tracking reference), list2 is a tracking handle. You need an
address-of operator to make a handle from a reference.

It works because it's a generic declaration, not a template
declaration. Generic type parameters can only be instantiated with
handles for ref types - so, for a specific instantiation, TList would
be something like List<T>^, and not just plain List<T>.

Hmmm. Then the constraint line makes little sense. A tracking handle
doesn't implement an interface, the type of the referenced object does. I
realize this is connected to the .NET behavior of following different rules
when instantiating generics using ref types vs value types, and there
probably is no perfectly consistent syntax which expresses the behavior.


.

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