CWG Issue 1471 (original) (raw)

This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 117a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2025-04-13

1471. Nested type of non-dependent base

Section: 13.8.3.2 [temp.dep.type]Status: CD3Submitter: Johannes SchaubDate: 2012-02-26

[Moved to DR at the April, 2013 meeting.]

Even though A::C is a nested type and member of the current instantiation, and thus dependent by the rules of 13.8.3.2 [temp.dep.type] paragraph 8, there does not seem to be a good reason for making it so:

struct B { struct C { }; };

template struct A : B { A::C c; };

Proposed resolution (October, 2012):

[Some existing uses of the term “member of the current instantiation” are consistent with the definition in 13.8.3.2 [temp.dep.type] paragraph 4; others are intended to refer to members of the “current instantiation,” as defined in paragraph 1. The following resolution changes the latter to use the phrase “member of a class that is the current instantiation.”]

1. Change 13.8.3.2 [temp.dep.type] paragraph 4 as follows:

A name is a member of the current instantiation if it is

• An unqualified name that, when looked up, refers to at least one member of a class that is the current instantiation or a non-dependent base class thereof. [_Note:_This can only occur when looking up a name in a scope enclosed by the definition of a class template. —_end note_]
• A qualified-id in which the _nested-name-specifier_refers to the current instantiation and that, when looked up, refers to at least one member of a class that is the current instantiation or a non-dependent base class thereof. [Note: if no such member is found, and the current instantiation has any dependent base classes, then the qualified-id is a member of an unknown specialization; see below. —_end note_]
• An id-expression denoting the member in a class member access expression (7.6.1.5 [expr.ref]) for which the type of the object expression is the current instantiation, and the_id-expression_, when looked up (_N4868_.6.5.6 [basic.lookup.classref]), refers to at least one member of a class that is the current instantiation or a non-dependent base class thereof. [Note: if no such member is found, and the current instantiation has any dependent base classes, then the_id-expression_ is a member of an unknown specialization; see below. —_end note_]

[Example: ... —_end example_]

A name is a _dependent member of the current instantiation_if it is a member of the current instantiation which, when looked up, refers to at least one member of a class that is the current instantiation.

1. Change 13.8.3.2 [temp.dep.type] paragraph 5 as follows:

A name is a member of an unknown specialization if it is

• A qualified-id in which the_nested-name-specifier_ names a dependent type that is not the current instantiation.
• A qualified-id in which the nested-name-specifier_refers to the current instantiation, the current instantiation has at least one dependent base class, and name lookup of the_qualified-id does not find any member of a class that is the current instantiation or a non-dependent base class thereof.
• An id-expression denoting the member in a class member access expression (7.6.1.5 [expr.ref]) in which either
  • the type of the object expression is the current instantiation, the current instantiation has at least one dependent base class, and name lookup of the id-expression does not find a member of a class that is the current instantiation or a non-dependent base class thereof; or
  • the type of the object expression is dependent and is not the current instantiation.

1. Change 13.8.3.2 [temp.dep.type] paragraph 8 as follows:

A type is dependent if it is

• ...
• a nested class or enumeration that is a dependentmember of the current instantiation,
• ...

1. Change 13.8.3.3 [temp.dep.expr] paragraph 3 as follows:

An id-expression is type-dependent if it contains

• ...

or if it names a static data dependent member of the current instantiation that has is a static data member of type “array of unknown bound ofT” for some T (13.7.2.5 [temp.static]). Expressions of the following forms...

1. Change 13.8.3.4 [temp.dep.constexpr] paragraph 2 as follows (assumes the base text is as modified by issue 1413):

An id-expression is value-dependent if:

• it is a name declared with a dependent type,
• it is the name of a non-type template parameter,
• it names a member of an unknown specialization,
• it names a static data member of the current instantiation that is a dependent member of the current instantiation and is not initialized in a_member-declarator_,
• it names a static member function that is adependent member of the current instantiation, or
• it is a constant with literal type and is initialized with an expression that is value-dependent.

Expressions of the following form...

1. Change 13.8.3.4 [temp.dep.constexpr] paragraph 5 as follows (assumes the base text is as modified by issue 1413):

An expression of the form &qualified-id where the_qualified-id_'s nested-name-specifier namesa dependent member of the current instantiation is value-dependent.