Re: [PATCH v21 20/23] c++: Implement __is_invocable built-in trait

[Ken Matsui <kmatsui@cs.washington.edu>]

On Tue, May 7, 2024 at 11:36 AM Jason Merrill <jason@redhat.com> wrote:
>
> On 5/3/24 16:52, Ken Matsui wrote:
> > Fixed datum reference problem.  Ok for trunk?
> >
> > -- >8 --
> >
> > This patch implements built-in trait for std::is_invocable.
> >
> > gcc/cp/ChangeLog:
> >
> >       * cp-trait.def: Define __is_invocable.
> >       * constraint.cc (diagnose_trait_expr): Handle CPTK_IS_INVOCABLE.
> >       * semantics.cc (trait_expr_value): Likewise.
> >       (finish_trait_expr): Likewise.
> >       * cp-tree.h (build_invoke): New function.
> >       * method.cc (build_invoke): New function.
> >
> > gcc/testsuite/ChangeLog:
> >
> >       * g++.dg/ext/has-builtin-1.C: Test existence of __is_invocable.
> >       * g++.dg/ext/is_invocable1.C: New test.
> >       * g++.dg/ext/is_invocable2.C: New test.
> >       * g++.dg/ext/is_invocable3.C: New test.
> >       * g++.dg/ext/is_invocable4.C: New test.
> >
> > Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> > ---
> >   gcc/cp/constraint.cc                     |   6 +
> >   gcc/cp/cp-trait.def                      |   1 +
> >   gcc/cp/cp-tree.h                         |   2 +
> >   gcc/cp/method.cc                         | 137 +++++++++
> >   gcc/cp/semantics.cc                      |   5 +
> >   gcc/testsuite/g++.dg/ext/has-builtin-1.C |   3 +
> >   gcc/testsuite/g++.dg/ext/is_invocable1.C | 349 +++++++++++++++++++++++
> >   gcc/testsuite/g++.dg/ext/is_invocable2.C | 139 +++++++++
> >   gcc/testsuite/g++.dg/ext/is_invocable3.C |  51 ++++
> >   gcc/testsuite/g++.dg/ext/is_invocable4.C |  33 +++
> >   10 files changed, 726 insertions(+)
> >   create mode 100644 gcc/testsuite/g++.dg/ext/is_invocable1.C
> >   create mode 100644 gcc/testsuite/g++.dg/ext/is_invocable2.C
> >   create mode 100644 gcc/testsuite/g++.dg/ext/is_invocable3.C
> >   create mode 100644 gcc/testsuite/g++.dg/ext/is_invocable4.C
> >
> > diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> > index c28d7bf428e..6d14ef7dcc7 100644
> > --- a/gcc/cp/constraint.cc
> > +++ b/gcc/cp/constraint.cc
> > @@ -3792,6 +3792,12 @@ diagnose_trait_expr (tree expr, tree args)
> >       case CPTK_IS_FUNCTION:
> >         inform (loc, "  %qT is not a function", t1);
> >         break;
> > +    case CPTK_IS_INVOCABLE:
> > +      if (!t2)
> > +    inform (loc, "  %qT is not invocable", t1);
> > +      else
> > +    inform (loc, "  %qT is not invocable by %qE", t1, t2);
> > +      break;
> >       case CPTK_IS_LAYOUT_COMPATIBLE:
> >         inform (loc, "  %qT is not layout compatible with %qT", t1, t2);
> >         break;
> > diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
> > index b1c875a6e7d..4e420d5390a 100644
> > --- a/gcc/cp/cp-trait.def
> > +++ b/gcc/cp/cp-trait.def
> > @@ -75,6 +75,7 @@ DEFTRAIT_EXPR (IS_EMPTY, "__is_empty", 1)
> >   DEFTRAIT_EXPR (IS_ENUM, "__is_enum", 1)
> >   DEFTRAIT_EXPR (IS_FINAL, "__is_final", 1)
> >   DEFTRAIT_EXPR (IS_FUNCTION, "__is_function", 1)
> > +DEFTRAIT_EXPR (IS_INVOCABLE, "__is_invocable", -1)
> >   DEFTRAIT_EXPR (IS_LAYOUT_COMPATIBLE, "__is_layout_compatible", 2)
> >   DEFTRAIT_EXPR (IS_LITERAL_TYPE, "__is_literal_type", 1)
> >   DEFTRAIT_EXPR (IS_MEMBER_FUNCTION_POINTER, "__is_member_function_pointer", 1)
> > diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> > index 52d6841559c..8aa41f7147f 100644
> > --- a/gcc/cp/cp-tree.h
> > +++ b/gcc/cp/cp-tree.h
> > @@ -7340,6 +7340,8 @@ extern tree get_copy_assign                     (tree);
> >   extern tree get_default_ctor                        (tree);
> >   extern tree get_dtor                                (tree, tsubst_flags_t);
> >   extern tree build_stub_object                       (tree);
> > +extern tree build_invoke                     (tree, const_tree,
> > +                                              tsubst_flags_t);
> >   extern tree strip_inheriting_ctors          (tree);
> >   extern tree inherited_ctor_binfo            (tree);
> >   extern bool base_ctor_omit_inherited_parms  (tree);
> > diff --git a/gcc/cp/method.cc b/gcc/cp/method.cc
> > index 08a3d34fb01..80791227a0a 100644
> > --- a/gcc/cp/method.cc
> > +++ b/gcc/cp/method.cc
> > @@ -1928,6 +1928,143 @@ build_trait_object (tree type)
> >     return build_stub_object (type);
> >   }
> >
> > +/* [func.require] Build an expression of INVOKE(FN_TYPE, ARG_TYPES...).  If the
> > +   given is not invocable, returns error_mark_node.  */
> > +
> > +tree
> > +build_invoke (tree fn_type, const_tree arg_types, tsubst_flags_t complain)
> > +{
> > +  if (error_operand_p (fn_type) || error_operand_p (arg_types))
> > +    return error_mark_node;
> > +
> > +  gcc_assert (TYPE_P (fn_type));
> > +  gcc_assert (TREE_CODE (arg_types) == TREE_VEC);
> > +
> > +  /* Access check is required to determine if the given is invocable.  */
> > +  deferring_access_check_sentinel acs (dk_no_deferred);
> > +
> > +  /* INVOKE is an unevaluated context.  */
> > +  cp_unevaluated cp_uneval_guard;
> > +
> > +  bool is_ptrdatamem;
> > +  bool is_ptrmemfunc;
> > +  if (TREE_CODE (fn_type) == REFERENCE_TYPE)
> > +    {
> > +      tree deref_fn_type = TREE_TYPE (fn_type);
> > +      is_ptrdatamem = TYPE_PTRDATAMEM_P (deref_fn_type);
> > +      is_ptrmemfunc = TYPE_PTRMEMFUNC_P (deref_fn_type);
> > +
> > +      /* Dereference fn_type if it is a pointer to member.  */
> > +      if (is_ptrdatamem || is_ptrmemfunc)
> > +     fn_type = deref_fn_type;
> > +    }
> > +  else
> > +    {
> > +      is_ptrdatamem = TYPE_PTRDATAMEM_P (fn_type);
> > +      is_ptrmemfunc = TYPE_PTRMEMFUNC_P (fn_type);
> > +    }
> > +
> > +  if (is_ptrdatamem && TREE_VEC_LENGTH (arg_types) != 1)
> > +    {
> > +      if (complain & tf_error)
> > +     error ("pointer to data member type %qT can only be invoked with "
> > +            "one argument", fn_type);
> > +      return error_mark_node;
> > +    }
> > +
> > +  if (is_ptrmemfunc && TREE_VEC_LENGTH (arg_types) == 0)
> > +    {
> > +      if (complain & tf_error)
> > +     error ("pointer to member function type %qT must be invoked with "
> > +            "at least one argument", fn_type);
> > +      return error_mark_node;
> > +    }
> > +
> > +  /* Construct an expression of a pointer to member.  */
> > +  tree ptrmem_expr;
> > +  if (is_ptrdatamem || is_ptrmemfunc)
> > +    {
> > +      tree datum_type = TREE_VEC_ELT (arg_types, 0);
> > +
> > +      /* datum must be a class type or a reference/pointer to a class type.  */
> > +      if (!(CLASS_TYPE_P (datum_type)
> > +         || ((TYPE_REF_P (datum_type) || POINTER_TYPE_P (datum_type))
> > +             && CLASS_TYPE_P (TREE_TYPE (datum_type)))))
> > +     {
> > +       if (complain & tf_error)
> > +         error ("first argument type %qT of a pointer to member must be "
> > +                "a class type or a reference/pointer to a class type",
> > +                datum_type);
> > +       return error_mark_node;
> > +     }
> > +
> > +      tree datum_expr = build_trait_object (datum_type);
> > +      datum_type = TREE_TYPE (datum_expr);
> > +
> > +      bool datum_is_refwrap = false;
> > +      if (CLASS_TYPE_P (datum_type))
> > +     {
> > +       /* 1.2 & 1.5: Handle std::reference_wrapper.  */
> > +       tree datum_decl = TYPE_NAME (TYPE_MAIN_VARIANT (datum_type));
> > +       if (decl_in_std_namespace_p (datum_decl))
> > +         {
> > +           const_tree name = DECL_NAME (datum_decl);
> > +           if (name && (id_equal (name, "reference_wrapper")))
> > +             {
> > +               /* Retrieve T from std::reference_wrapper<T>,
> > +                  i.e., decltype(datum.get()).  */
> > +               datum_type = TREE_VEC_ELT (TYPE_TI_ARGS (datum_type), 0);
> > +               datum_is_refwrap = true;
>
> Hmm, with datum_expr moved up as I suggested, it's now wrong for the
> reference_wrapper case.  So either we need to override it here, or move
> it back down and do something else to handle reference to
> reference_wrapper, like another local variable non_ref_datum_type or
> something.

Ahh, I totally missed this!  Thank you for your review!  Let me think of this.

>
> Jason
>