https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69178
Bug ID: 69178
Summary: [concepts] An invalid expression in a
requires-expression is evaluated too eagerly
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: ville.voutilainen at gmail dot com
Target Milestone: ---
Test snippet:
template <class T> struct S : T {};
template <class T> concept bool ConcreteDerivableFrom()
{
return requires()
{
S<T>();
};
}
struct X final {};
template <ConcreteDerivableFrom C>
void f() {}
template <class T>
void f() {}
int main()
{
f<X>();
}
Fails with
prog.cc: In instantiation of 'struct S<X>':
prog.cc:20:10: required from here
prog.cc:1:27: error: cannot derive from 'final' base 'X' in derived type 'S<X>'
template <class T> struct S : T {};
^
