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

1204. Specifiers in a for-range-declaration

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

It seems unfortunate that the beginning of a C-style for loop can look like

for ( attribute-specifier_opt decl-specifier-seq_opt declarator

whereas the beginning of a range-based for loop looks like

for ( attribute-specifier_opt type-specifier-seq_opt declarator

So that we don't know what constraints we are trying to apply to the specifiers until we see, or don't see, a :. The inconsistency between decl-specifier-seq and type-specifier-seq seems gratuitous and inconvenient.

Proposed resolution (November, 2010) [SUPERSEDED]:

1. Change the grammar 8.6 [stmt.iter] paragraph 1 as follows:

for-range-declaration:
attribute-specifier_opt type-specifier-seq decl-specifier-seq declarator

2. Add the following as a new paragraph at the end of 8.6.5 [stmt.ranged]:

The the decl-specifier-seq of a for-range-declaration, each decl-specifier shall be either a type-specifier or constexpr.