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2498. operator>>(basic_istream&&, T&&) returns basic_istream&, but should probably return basic_istream&&

Section: 31.7.5.6 [istream.rvalue] Status: Resolved Submitter: Richard Smith Opened: 2015-05-08 Last modified: 2020-11-09

Priority: 3

View all other issues in [istream.rvalue].

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Discussion:

Consider: 

auto& is = make_istream() >> x; // oops, istream object is already gone

With a basic_istream&& return type, the above would be ill-formed, and generally we'd preserve the value category properly.

[2015-06, Telecon]

JW: think this needs proper consideration, it would make 

stream() >> x >> y >> z
go from 3 operator>> calls to 6 operator>> calls, and wouldn't prevent dangling references (change the example to auto&&)

[2020-02 Resolved by the adoption of 1203 in Prague.]

[2020-11-09 Resolved for C++20. Status changed: Tentatively Resolved → Resolved.]

Proposed resolution: