CWG3138 [expr.prim.id.unqual] name of coroutine parameter copy inside a lambda

[t3nsor]

Full name of submitter: Brian Bi

Issue description: After P2900R14, in cases where [expr.prim.id.unqual]/3+a applies, we do not fall through to 3+b, which says that the result of the unqualified-id is the parameter copy. Therefore, the result now refers to the original parameter.

Suggested resolution: We should keep all the description of what entity the unqualified-id refers to in p3.

Edit [expr.prim.id.unqual]/3:

The result is the entity denoted by the unqualified-id ([basic.lookup.unqual]), except that if that entity is a coroutine parameter, the result is instead the copy of that parameter ([dcl.fct.def.coroutine]).

Edit [expr.prim.id.unqual]/3+b:

Otherwise, if the unqualified-id names entity is the copy of a coroutine parameter, the type of the expression is that of the copy of the parameter ([dcl.fct.def.coroutine]), and the result is that copy. the type of the entity.

[t3nsor]

Here is some new wording, rebased on the current draft, that also resolves https://lists.isocpp.org/core/2025/02/17328.php

Edit [expr.prim.id.unqual]/3:

The result is the entity denoted by the unqualified-id ([basic.lookup.unqual]), except that if that entity is a parameter declared in the function parameter scope associated with a coroutine definition, the result is instead the copy of that parameter ([dcl.fct.def.coroutine]).

Move [expr.prim.id.unqual]/7 immediately after p3 and edit it as follows:

Otherwise, ifIf the unqualified-id appears in the predicate of a contract assertion C ([basic.contract]) and the entityresult is

• a variable declared outside of C of object type T,
• a variable or template parameter of reference type declared outside of C of type “reference to T”, or
• a structured binding of type T whose corresponding variable is declared outside of C,

then the type of the expression is const T , where T is the type that the expression would otherwise have according to the rules below.

Edit [expr.prim.id.unqual]/5:

Otherwise, if the unqualified-id names result is the copy of a coroutine parameter, the type of the expression is that of the copy of the parameter ([dcl.fct.def.coroutine]), and the result is that copy. the type of the result.

[t3nsor]

Actually, p5 may not be needed anymore after the other changes.

[jensmaurer]

CWG3138