CWG3005 [basic.scope.scope] Function parameters can be name-independent

[Eisenwave]

Reference (section label): [basic.scope.scope] pargraph 5, bullet 1

Link to reflector thread (if any):

Issue description

From P2169R4:

In Varna, EWG decided not to support function parameter names and requires clauses parameter as these can remained unamed without semantics differences.

See also poll: https://github.com/cplusplus/papers/issues/878#issuecomment-1594534611

This design was not worded correctly because [basic.scope.scope] paragraph 5, bullet 1 permits all variables with automatic storage duration named _ to be name-independent, including function parameters.

Suggested resolution

Change [basic.scope.scope] paragraph 5 as follows:

A declaration is name-independent if its name is _ (U+005F LOW LINE) and it declares

• a variable with automatic storage duration other than a function parameter,
• a structured binding with no storage-class-specifier and not inhabiting a namespace scope,
• the variable introduced by an init-capture, or
• a non-static data member of other than an anonymous union.

Recommended practice: Implementations should not emit a warning that a name-independent declaration is used or unused.

[Eisenwave]

Note that cplusplus/draft#7728 also changes the same paragraph; maybe we can do that editorial change as a drive-by in here.

[jensmaurer]

CWG3005