Behavior of decltype

Question

Say I have an object of some of stl container classes obj. I can define other object of same type this way:

decltype(obj) obj2;

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Answer 1

Your code is well-formed according to the final C++0x draft (FDIS). This was a late change that's not yet been implemented by the Visual Studio compiler.

In the meantime, a workaround is to use a typedef:

typedef decltype(obj) obj_type;
obj_type::iterator it = obj.begin();

EDIT: The relevant chapter and verse is 5.1.1/8:

qualified-id:
    [...]
    nested-name-specifier templateopt unqualified-id

nested-name-specifier:
    [...]
    decltype-specifier ::

decltype-specifier:
    decltype ( expression )

And for completeness's sake:

The original core issue

Proposal for wording