Ping.
On Fri, Sep 18, 2020 at 04:05:16PM -0400, Marek Polacek via Gcc-patches wrote:
> Ping.
>
> On Thu, Sep 10, 2020 at 06:15:24PM -0400, Marek Polacek via Gcc-patches wrote:
> > To quickly recap, P0846 says that a name is also considered to refer to
> > a template if it is an unqualified-id followed by a < and name lookup
> > finds either one or more functions or finds nothing.
> >
> > In a template, when parsing a function call that has type-dependent
> > arguments, we can't perform ADL right away so we set KOENIG_LOOKUP_P in
> > the call to remember to do it when instantiating the call
> > (tsubst_copy_and_build/CALL_EXPR). When the called function is a
> > function template, we represent the call with a TEMPLATE_ID_EXPR;
> > usually the operand is an OVERLOAD.
> >
> > In the P0846 case though, the operand can be an IDENTIFIER_NODE, when
> > name lookup found nothing when parsing the template name. But we
> > weren't handling this correctly in tsubst_copy_and_build. First
> > we need to pass the FUNCTION_P argument from <case TEMPLATE_ID_EXPR> to
> > <case IDENTIFIER_NODE>, otherwise we give a bogus error. And then in
> > <case CALL_EXPR> we need to perform ADL. The rest of the changes is to
> > give better errors when ADL didn't find anything.
> >
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> > I think I'd like to backport to 10 too.
> >
> > gcc/cp/ChangeLog:
> >
> > PR c++/97010
> > * pt.c (tsubst_copy_and_build) <case TEMPLATE_ID_EXPR>: Call
> > tsubst_copy_and_build explicitly instead of using the RECUR macro.
> > Handle a TEMPLATE_ID_EXPR with an IDENTIFIER_NODE as its operand.
> > <case CALL_EXPR>: Perform ADL for a TEMPLATE_ID_EXPR with an
> > IDENTIFIER_NODE as its operand.
> >
> > gcc/testsuite/ChangeLog:
> >
> > PR c++/97010
> > * g++.dg/cpp2a/fn-template21.C: New test.
> > * g++.dg/cpp2a/fn-template22.C: New test.
> > ---
> > gcc/cp/pt.c | 37 ++++++++++++++++------
> > gcc/testsuite/g++.dg/cpp2a/fn-template21.C | 24 ++++++++++++++
> > gcc/testsuite/g++.dg/cpp2a/fn-template22.C | 25 +++++++++++++++
> > 3 files changed, 77 insertions(+), 9 deletions(-)
> > create mode 100644 gcc/testsuite/g++.dg/cpp2a/fn-template21.C
> > create mode 100644 gcc/testsuite/g++.dg/cpp2a/fn-template22.C
> >
> > diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
> > index 30c6735dede..566e24f9bf3 100644
> > --- a/gcc/cp/pt.c
> > +++ b/gcc/cp/pt.c
> > @@ -19241,7 +19241,8 @@ out:
> > }
> >
> > /* Like tsubst but deals with expressions and performs semantic
> > - analysis. FUNCTION_P is true if T is the "F" in "F (ARGS)". */
> > + analysis. FUNCTION_P is true if T is the "F" in "F (ARGS)" or
> > + "F<TARGS> (ARGS)". */
> >
> > tree
> > tsubst_copy_and_build (tree t,
> > @@ -19323,7 +19324,10 @@ tsubst_copy_and_build (tree t,
> > case TEMPLATE_ID_EXPR:
> > {
> > tree object;
> > - tree templ = RECUR (TREE_OPERAND (t, 0));
> > + tree templ = tsubst_copy_and_build (TREE_OPERAND (t, 0), args,
> > + complain, in_decl,
> > + function_p,
> > + integral_constant_expression_p);
> > tree targs = TREE_OPERAND (t, 1);
> >
> > if (targs)
> > @@ -19370,13 +19374,21 @@ tsubst_copy_and_build (tree t,
> > }
> > else
> > object = NULL_TREE;
> > - templ = lookup_template_function (templ, targs);
> > +
> > + tree tid = lookup_template_function (templ, targs);
> >
> > if (object)
> > - RETURN (build3 (COMPONENT_REF, TREE_TYPE (templ),
> > - object, templ, NULL_TREE));
> > + RETURN (build3 (COMPONENT_REF, TREE_TYPE (tid),
> > + object, tid, NULL_TREE));
> > + else if (identifier_p (templ))
> > + {
> > + /* C++20 P0846: we can encounter an IDENTIFIER_NODE here when
> > + name lookup found nothing when parsing the template name. */
> > + gcc_assert (cxx_dialect >= cxx20 || seen_error ());
> > + RETURN (tid);
> > + }
> > else
> > - RETURN (baselink_for_fns (templ));
> > + RETURN (baselink_for_fns (tid));
> > }
> >
> > case INDIRECT_REF:
> > @@ -19967,14 +19979,17 @@ tsubst_copy_and_build (tree t,
> >
> > /* We do not perform argument-dependent lookup if normal
> > lookup finds a non-function, in accordance with the
> > - expected resolution of DR 218. */
> > + resolution of DR 218. */
> > if (koenig_p
> > && ((is_overloaded_fn (function)
> > /* If lookup found a member function, the Koenig lookup is
> > not appropriate, even if an unqualified-name was used
> > to denote the function. */
> > && !DECL_FUNCTION_MEMBER_P (get_first_fn (function)))
> > - || identifier_p (function))
> > + || identifier_p (function)
> > + /* C++20 P0846: Lookup found nothing. */
> > + || (TREE_CODE (function) == TEMPLATE_ID_EXPR
> > + && identifier_p (TREE_OPERAND (function, 0))))
> > /* Only do this when substitution turns a dependent call
> > into a non-dependent call. */
> > && type_dependent_expression_p_push (t)
> > @@ -19982,9 +19997,13 @@ tsubst_copy_and_build (tree t,
> > function = perform_koenig_lookup (function, call_args, tf_none);
> >
> > if (function != NULL_TREE
> > - && identifier_p (function)
> > + && (identifier_p (function)
> > + || (TREE_CODE (function) == TEMPLATE_ID_EXPR
> > + && identifier_p (TREE_OPERAND (function, 0))))
> > && !any_type_dependent_arguments_p (call_args))
> > {
> > + if (TREE_CODE (function) == TEMPLATE_ID_EXPR)
> > + function = TREE_OPERAND (function, 0);
> > if (koenig_p && (complain & tf_warning_or_error))
> > {
> > /* For backwards compatibility and good diagnostics, try
> > diff --git a/gcc/testsuite/g++.dg/cpp2a/fn-template21.C
> > b/gcc/testsuite/g++.dg/cpp2a/fn-template21.C
> > new file mode 100644
> > index 00000000000..7b3f26bbfa0
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp2a/fn-template21.C
> > @@ -0,0 +1,24 @@
> > +// PR c++/97010
> > +// { dg-do compile { target c++20 } }
> > +
> > +namespace M {
> > + struct S { int x; };
> > + S foo ();
> > +
> > + template<typename>
> > + void get (S);
> > +}
> > +
> > +template<typename T>
> > +void bar (const T& t)
> > +{
> > + get<int>(t);
> > +}
> > +
> > +int
> > +main ()
> > +{
> > + auto a = M::foo ();
> > + get<int>(a);
> > + bar (a);
> > +}
> > diff --git a/gcc/testsuite/g++.dg/cpp2a/fn-template22.C
> > b/gcc/testsuite/g++.dg/cpp2a/fn-template22.C
> > new file mode 100644
> > index 00000000000..62cc81db0c7
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp2a/fn-template22.C
> > @@ -0,0 +1,25 @@
> > +// PR c++/97010
> > +// { dg-do compile { target c++20 } }
> > +
> > +namespace M {
> > + struct S { int x; };
> > + S foo ();
> > +
> > +// Test not-found-by-ADL scenario.
> > +// template<typename>
> > +// void get (S);
> > +}
> > +
> > +template<typename T>
> > +void bar (const T& t)
> > +{
> > + get<int>(t); // { dg-error ".get. was not declared in this scope" }
> > +}
> > +
> > +int
> > +main ()
> > +{
> > + auto a = M::foo ();
> > + get<int>(a); // { dg-error ".get. was not declared in this scope" }
> > + bar (a);
> > +}
> >
> > base-commit: af47a2035a4882e6d4506e3d00b5a42414e3ee2b
> > --
> > 2.26.2
> >
>
Marek
