On Tue, 19 Sep 2023, Patrick Palka wrote:
> On Tue, 19 Sep 2023, Jason Merrill wrote:
>
> > On 9/19/23 12:40, Patrick Palka wrote:
> > > Tested on x86_64-pc-linux-gnu, does this look OK for trunk/13?
> >
> > OK for trunk. What's your argument for backporting?
>
> Thanks. I don't feel strongly about it, but I was thinking that since
> we typically backport C++20-only correctness fixes to the most recent
> release branch, C++20-only diagnostic improvements might be suitable
> too?
>
> >
> > > -- >8 --
> > >
> > > 1. Move class NTTP object pretty printing to a more general spot in
> > > the pretty printer.
FWIW this first change isn't just a refactoring, it means we now pretty
print an NTTP object that appears elsewhere besides in a template
argument list, e.g. in a parameter mapping:
Before:
diagnostic19.C:8:15: note: the expression ‘((const A)V).value [with V =
_ZTAXtl1AEE]’ evaluated to ‘false’
After:
diagnostic19.C:8:15: note: the expression ‘(V).value [with V = A{false}]’
evaluated to ‘false’
> > > 2. Print the type of an class NTTP object alongside its CONSTRUCTOR
> > > value, like dump_expr would have done.
> > > 3. Don't pretty print const VIEW_CONVERT_EXPR wrapping class NTTPs.
> > >
> > > PR c++/111471
> > >
> > > gcc/cp/ChangeLog:
> > >
> > > * cxx-pretty-print.cc (cxx_pretty_printer::expression)
> > > <case VAR_DECL>: Print the value of a class NTTP object.
> > > <case VIEW_CONVERT_EXPR>: Strip cosnt VIEW_CONVERT_EXPR
> > > wrappers for class NTTPs.
> > > (pp_cxx_template_argument_list): Don't handle the class
> > > NTTP objects here.
> > >
> > > gcc/testsuite/ChangeLog:
> > >
> > > * g++.dg/concepts/diagnostic19.C: New test.
> > > ---
> > > gcc/cp/cxx-pretty-print.cc | 19 +++++++++++++++++--
> > > gcc/testsuite/g++.dg/concepts/diagnostic19.C | 20 ++++++++++++++++++++
> > > 2 files changed, 37 insertions(+), 2 deletions(-)
> > > create mode 100644 gcc/testsuite/g++.dg/concepts/diagnostic19.C
> > >
> > > diff --git a/gcc/cp/cxx-pretty-print.cc b/gcc/cp/cxx-pretty-print.cc
> > > index 909a9dc917f..7cd43151592 100644
> > > --- a/gcc/cp/cxx-pretty-print.cc
> > > +++ b/gcc/cp/cxx-pretty-print.cc
> > > @@ -1121,6 +1121,15 @@ cxx_pretty_printer::expression (tree t)
> > > t = OVL_FIRST (t);
> > > /* FALLTHRU */
> > > case VAR_DECL:
> > > + if (DECL_NTTP_OBJECT_P (t))
> > > + {
> > > + /* Print the type followed by the CONSTRUCTOR value of an
> > > + NTTP object. */
> > > + simple_type_specifier (cv_unqualified (TREE_TYPE (t)));
> > > + expression (DECL_INITIAL (t));
> > > + break;
> > > + }
> > > + /* FALLTHRU */
> > > case PARM_DECL:
> > > case FIELD_DECL:
> > > case CONST_DECL:
> > > @@ -1261,6 +1270,14 @@ cxx_pretty_printer::expression (tree t)
> > > pp_cxx_right_paren (this);
> > > break;
> > > + case VIEW_CONVERT_EXPR:
> > > + if (TREE_CODE (TREE_OPERAND (t, 0)) == TEMPLATE_PARM_INDEX)
> > > + {
> > > + /* Strip const VIEW_CONVERT_EXPR wrappers for class NTTPs. */
> > > + expression (TREE_OPERAND (t, 0));
> > > + break;
> > > + }
> > > + /* FALLTHRU */
> > > default:
> > > c_pretty_printer::expression (t);
> > > break;
> > > @@ -1966,8 +1983,6 @@ pp_cxx_template_argument_list (cxx_pretty_printer
> > > *pp,
> > > tree t)
> > > if (TYPE_P (arg) || (TREE_CODE (arg) == TEMPLATE_DECL
> > > && TYPE_P (DECL_TEMPLATE_RESULT (arg))))
> > > pp->type_id (arg);
> > > - else if (VAR_P (arg) && DECL_NTTP_OBJECT_P (arg))
> > > - pp->expression (DECL_INITIAL (arg));
> > > else
> > > pp->expression (arg);
> > > }
> > > diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic19.C
> > > b/gcc/testsuite/g++.dg/concepts/diagnostic19.C
> > > new file mode 100644
> > > index 00000000000..20cdb63380b
> > > --- /dev/null
> > > +++ b/gcc/testsuite/g++.dg/concepts/diagnostic19.C
> > > @@ -0,0 +1,20 @@
> > > +// Verify our pretty printing of class NTTP objects.
> > > +// PR c++/111471
> > > +// { dg-do compile { target c++20 } }
> > > +
> > > +struct A { bool value; };
> > > +
> > > +template<A V>
> > > + requires (V.value) // { dg-message {'\(V\).value \[with V =
> > > A\{false\}\]'} }
> > > +void f();
> > > +
> > > +template<A V> struct B { static constexpr auto value = V.value; };
> > > +
> > > +template<class T>
> > > + requires T::value // { dg-message {'T::value \[with T =
> > > B<A\{false\}>\]'}
> > > }
> > > +void g();
> > > +
> > > +int main() {
> > > + f<A{false}>(); // { dg-error "no match" }
> > > + g<B<A{false}>>(); // { dg-error "no match" }
> > > +}
> >
> >
>
