[Moved to DR at the November, 2014 meeting.]

Proposed resolution (October, 2014):

Change 7.5.6 [expr.prim.lambda] paragraph 20 as follows:

The closure type associated with a lambda-expression has a deleted (9.5.3 [dcl.fct.def.delete]) no default constructor and a deleted copy assignment operator. It has an implicitly-declared a defaulted copy constructor (11.4.5.3 [class.copy.ctor]) and may have an implicitly-declared and a defaulted move constructor (11.4.5.3 [class.copy.ctor]). [Note: The copy/move constructor is implicitly defined in the same way as any other implicitly declared copy/move constructor would be implicitly defined These special member functions are implicitly defined as usual, and might therefore be defined as deleted. —end note]

According to 7.5.6 [expr.prim.lambda] paragraph 20,

The closure type associated with a lambda-expression has a deleted (9.5.3 [dcl.fct.def.delete]) default constructor and a deleted copy assignment operator. It has an implicitly-declared copy constructor (11.4.5.3 [class.copy.ctor]) and may have an implicitly-declared move constructor (11.4.5.3 [class.copy.ctor]).

However, according to 11.4.5.3 [class.copy.ctor] paragraph 9,

If the definition of a class X does not explicitly declare a move constructor, one will be implicitly declared as defaulted if and only if

• X does not have a user-declared copy constructor,

• X does not have a user-declared copy assignment operator,

• X does not have a user-declared move assignment operator, and

• X does not have a user-declared destructor.

It is not clear how this applies to the closure class. Would it be better to state that the closure class has a defaulted move constructor and a defaulted move assignment operator? There is already wording that handles the case if they are ultimately defined as deleted.