This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 116a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2024-12-19

1212. Non-function-call xvalues and decltype

[Voted into the WP at the March, 2011 meeting as part of paper N3262.]

Given

    int&& f();
    int i;

it is surprising that decltype(f()) and decltype(static_cast<int&&>(i)) are not the same type.

Proposed resolution (November, 2010) [SUPERSEDED]:

Change 9.2.9.3 [dcl.type.simple] paragraph 4 as follows:

The type denoted by decltype(e) is defined as follows:

• if e is an unparenthesized id-expression or a class member access (7.6.1.5 [expr.ref]), decltype(e) is the type of the entity named by e. If there is no such entity, or if e names a set of overloaded functions, the program is ill-formed;

• otherwise, if e is a function call (7.6.1.3 [expr.call]) or an invocation of an overloaded operator (parentheses around e are ignored), decltype(e) is the return type of the statically chosen function an xvalue, decltype(e) is T&&, where T is the type of e;

• otherwise, if e is an lvalue, decltype(e) is T&, where T is the type of e;

• otherwise, decltype(e) is the type of e.