http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51786
--- Comment #3 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2012-01-31 21:26:41 UTC --- It seems to me that all these examples should be rejected (Thanks to Jens Maurer for helping me here): At first it seems, that we can follow the grammar chain starting from /declaration/ in 7 [dcl.dcl] via simple-declaration => decl-specifier-seq_opt init-declarator-list_opt; without the optional init-declarator-list reaching decl-specifier => type-specifier => trailing-type-specifier => simple-type-specifier => decltype(expression). But the show-stopper for this is 7 [dcl.dcl] p3: "In a simple-declaration, the optional init-declarator-list can be omitted only when declaring a class (Clause 9) or enumeration (7.2), that is, when the decl-specifier-seq contains either a class-specifier, an elaborated-type- specifier with a class-key (9.1), or an enum-specifier. [..]" Neither of these three situations applies, so this is no valid /simple-declaration/.
