705. type-trait decay incompletely specified

Section: 21.3.9.7 [meta.trans.other] Status: CD1 Submitter: Thorsten Ottosen Opened: 2007-07-08 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

The current working draft has a type-trait decay in 21.3.9.7 [meta.trans.other].

Its use is to turn C++03 pass-by-value parameters into efficient C++0x pass-by-rvalue-reference parameters. However, the current definition introduces an incompatible change where the cv-qualification of the parameter type is retained. The deduced type should loose such cv-qualification, as pass-by-value does.

Proposed resolution:

In 21.3.9.7 [meta.trans.other] change the last sentence:

Otherwise the member typedef type equals remove_cv<U>::type.

In 22.4.5 [tuple.creation]/1 change:

where each Vi in VTypes is X& if, for the corresponding type Ti in Types, remove_cv<remove_reference<Ti>::type>::type equals reference_wrapper<X>, otherwise Vi is decay<Ti>::type. Let Ui be decay<Ti>::type for each Ti in Types. Then each Vi in VTypes is X& if Ui equals reference_wrapper<X>, otherwise Vi is Ui.