https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63999
Bug ID: 63999
Summary: Explcit conversion operators are not considered for
explicit cast using brace
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: tomaszkam at gmail dot com
For the following code:
struct bool_convert
{
explicit operator bool() { return true; }
};
bool x(bool_convert()); //1
bool x1{bool_convert{}}; //2
bool x2 = bool{bool_convert{}}; //3
Both line 1 and 2 compiles correcty, while the line 3 produces following error:
error: cannot convert 'bool_convert' to 'bool' in initialization.
According to the standard section $5.2.3 [expr.type.conv]/3:
Similarly, a simple-type-specifier or typename-specifier followed by a
braced-init-list creates a temporary
object of the specified type direct-list-initialized (8.5.4) with the specified
braced-init-list, and its value is
that temporary object as a prvalue.
That means that cast notation from the line 3 should have equivalent semantics
to the one from line 2.
Section $12.3.2 [class.conv.fct]/2:
A conversion function may be explicit (7.1.2), in which case it is only
considered as a user-defined conversion
for direct-initialization (8.5). Otherwise, user-defined conversions are not
restricted to use in assignments
and initializations.
Explicit conversion operator should be invoked for direct initialization so
behaviour for line 3 is incoorect and conversion operator should be used.
