GB-5: [utility.exchange] missing MoveConstructible/MoveAssignable requirement

[sdutoit]

N3733 GB-5 says:

The wording describes example code including the call of a move constructor, but there is no requirement stated that T be move constructible.

It goes on to propose:

We would like to add a new Para 1 before existing paragraph:
Requires: Type T shall be MoveConstructible (Table 20) and MoveAssignable (Table 22).
However the MoveAssignable concept currently does not cover cases where the source and destination types may differ.

[sdutoit]

Note: it's an effects clause, not an example.

[sdutoit]

Not a defect. Because the draft specifies "Equivalent to:", the requirements are already implicitly specified.

See [structure.specifications]/4:

Whenever the Effects: element specifies that the semantics of some function F are Equivalent to some code sequence, then the various elements are interpreted as follows. [...] the semantics of the code sequence are determined by the Requires:, Effects:, Postconditions:, Returns:, Throws:, Complexity:, Remarks:, Error conditions:, and Notes: specified for the function invocations contained in the code sequence.

[sdutoit]

LWG is opening an issue for this.