On Sat, Mar 24, 2018 at 6:59 AM, Marek Polacek <pola...@redhat.com> wrote: > Recently the code in finish_static_assert was changed to use > perform_implicit_conversion_flags followed by fold_non_dependent_expr. That > broke this test becase when in a template, p_i_c_f merely wraps the expr in > an IMPLICIT_CONV_EXPR. fold_non_dependent_expr should be able to fold it to > a constant but it gave up because is_nondependent_constant_expression returned > false. Jason suggested to fix this roughly like the following, i.e. consider > conversions from classes to literal types potentially constant. > > Bootstrapped/regtested on x86_64-linux, ok for trunk? > > 2018-03-24 Marek Polacek <pola...@redhat.com> > > PR c++/85032 > * constexpr.c (potential_constant_expression_1): Consider conversions > from classes to literal types potentially constant. > > * g++.dg/cpp0x/pr51225.C: Adjust error message. > * g++.dg/cpp1z/constexpr-if17.C: New test. > > diff --git gcc/cp/constexpr.c gcc/cp/constexpr.c > index bebd9f5b5d0..c4b5afe90a2 100644 > --- gcc/cp/constexpr.c > +++ gcc/cp/constexpr.c > @@ -5768,6 +5768,23 @@ potential_constant_expression_1 (tree t, bool > want_rval, bool strict, bool now, > TREE_TYPE (t)); > return false; > } > + /* This might be a conversion from a class to a literal type. Let's > + consider it potentially constant since the conversion might be > + a constexpr user-defined conversion. */ > + else if (cxx_dialect >= cxx11 > + && COMPLETE_TYPE_P (TREE_TYPE (t)) > + && literal_type_p (TREE_TYPE (t))
We probably need to allow dependent types here, too. And incomplete classes, which might turn out to be literal later. Jason
