Coroutine parameters passed to a promise constructor
9.5.4 [dcl.fct.def.coroutine]
Gor Nishanov

Created on 2020-10-19.00:00:00 last changed 6 months ago


Date: 2020-10-19.00:00:00

The resolution of issue 2436 (in P2107R0) deleted the sentence

A reference to a parameter in the function-body of the coroutine and in the call to the coroutine promise constructor is replaced by a reference to its copy.

replacing it with new wording in [expr.prim.id.unqual] paragraph 1:

An identifier that names a coroutine parameter refers to the copy of the parameter (9.5.4 [dcl.fct.def.coroutine]).

This new approach no longer covers coroutine parameters passed to a promise constructor, since the constructor call is implicit, as described in [expr.prim.id.unqual] paragraph 5.

Suggested resolution:

  1. Change [expr.prim.id.unqual] paragraph 4 as follows:

  2. In the following, pi is an lvalue of type Pi, where p1 denotes *this and pi+1 denotes the ith function parameter for a non-static member function, and pi denotes the ith function parameter otherwise. Let qi be the corresponding parameter copy, as described below.
  3. Change [expr.prim.id.unqual] bullet 5.7 as follows:

  4. A coroutine behaves as if its function-body were replaced by...

    • ...

    • promise-constructor-arguments is determined as follows: overload resolution is performed on a promise constructor call created by assembling an argument list with lvalues pq1 ... pqn. If a viable constructor is found (12.2.3 [over.match.viable]), then promise-constructor-arguments is (pq1, ... , pqn), otherwise promise-constructor-arguments is empty.

Date User Action Args
2020-10-19 00:00:00admincreate