Proposed resolution (October, 2019):

Change bullet 3.8 of 9.4.5 [dcl.init.list] as follows:

• Otherwise, if T is an enumeration with a fixed underlying type (9.7.1 [dcl.enum]) U, the initializer-list has a single element v, v can be implicitly converted to U, and the initialization is direct-list-initialization, the object is initialized with the value T(v) (7.6.1.4 [expr.type.conv]); if a narrowing conversion is required to convert v to the underlying type of T U, the program is ill-formed. [Example:...

Proposed resolution (May, 2019): [SUPERSEDED]

Change bullet 3.8 of 9.4.5 [dcl.init.list] as follows:

• Otherwise, if T is an enumeration with a fixed underlying type (9.7.1 [dcl.enum]), the initializer-list has a single element v, v can be implicitly converted to the underlying type of T, and the initialization is direct-list-initialization, the object is initialized with the value T(v) (7.6.1.4 [expr.type.conv]); if a narrowing conversion is required to convert v to the underlying type of T, the program is ill-formed. [Example:...

Notes from the October, 2018 teleconference:

CWG agreed with the suggested direction, along the lines of “...can be implicitly converted to the underlying type of T...”

[Adopted as a DR at the November, 2019 meeting.]

According to 9.4.5 [dcl.init.list] bullet 3.8,

• Otherwise, if T is an enumeration with a fixed underlying type (9.7.1 [dcl.enum]), the initializer-list has a single element v, and the initialization is direct-list-initialization, the object is initialized with the value T(v) (7.6.1.4 [expr.type.conv]); if a narrowing conversion is required to convert v to the underlying type of T, the program is ill-formed.

The conversion T(v) is too broad, allowing, e.g., conversion from a different scoped enumeration type. The intent presumably was only to allow v to be a value of T's underlying type.