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

2081. Deduced return type in redeclaration or specialization of function template

[Accepted as a DR at the March, 2018 (Jacksonville) meeting.]

9.2.9.7 [dcl.spec.auto] paragraph 13 says,

Redeclarations or specializations of a function or function template with a declared return type that uses a placeholder type shall also use that placeholder, not a deduced type.

The inverse should also be true (a specialization cannot use a placeholder type if the template used a non-placeholder), but this is not said explicitly.

Proposed resolution (November, 2017)

Change 9.2.9.7 [dcl.spec.auto] paragraph 11 as follows:

Redeclarations or specializations of a function or function template with a declared return type that uses a placeholder type shall also use that placeholder, not a deduced type. Similarly, redeclarations or specializations of a function or function template with a declared return type that does not use a placeholder type shall not use a placeholder. [Example: