Re: [PATCH v23 32/33] c++: Implement __is_invocable built-in trait

2024-02-19 Thread Ken Matsui 
On Mon, Oct 23, 2023 at 2:23 PM Jason Merrill  wrote:
>
> On 10/20/23 17:37, Patrick Palka wrote:
> > On Fri, 20 Oct 2023, Patrick Palka wrote:
> >
> >> On Fri, 20 Oct 2023, Patrick Palka wrote:
> >>
> >>> On Fri, 20 Oct 2023, Ken Matsui wrote:
> >>>
>  This patch implements built-in trait for std::is_invocable.
> >>>
> >>> Nice!  My email client unfortunately ate my first review attempt, so
> >>> apologies for my brevity this time around.
> >>>
>  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.
> (is_invocable_p): New function.
> * method.h: New file to export build_trait_object in method.cc.
>
> Given how much larger semantics.cc is than method.cc, maybe let's put
> is_invocable_p in method.cc instead?  And in general declarations can go
> in cp-tree.h.
>
>  diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
>  index 7cccbae5287..cc2e400531a 100644
>  --- a/gcc/cp/semantics.cc
>  +++ b/gcc/cp/semantics.cc
>  @@ -45,6 +45,10 @@ along with GCC; see the file COPYING3.  If not see
>    #include "gomp-constants.h"
>    #include "predict.h"
>    #include "memmodel.h"
>  +#include "method.h"
>  +
>  +#include "print-tree.h"
>  +#include "tree-pretty-print.h"
> 
>    /* There routines provide a modular interface to perform many parsing
>   operations.  They may therefore be used during actual parsing, or
>  @@ -11714,6 +11718,133 @@ classtype_has_nothrow_assign_or_copy_p (tree 
>  type, bool assign_p)
>  return saw_copy;
>    }
> 
>  +/* Return true if FN_TYPE is invocable with the given ARG_TYPES.  */
>  +
>  +static bool
>  +is_invocable_p (tree fn_type, tree arg_types)
> >
> > (Sorry for the spam)  We'll eventually want to implement a built-in for
> > invoke_result, so perhaps we should preemptively factor out the bulk
> > of this function into a 'build_INVOKE' helper function that returns the
> > built tree?
> >
>  +{
>  +  /* ARG_TYPES must be a TREE_VEC.  */
>  +  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);
>  +
>  +  /* std::is_invocable 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)
>  +/* A pointer to data member with non-one argument is not invocable. 
>   */
>  +return false;
>  +
>  +  if (is_ptrmemfunc && TREE_VEC_LENGTH (arg_types) == 0)
>  +/* A pointer to member function with no arguments is not invocable. 
>   */
>  +return false;
>  +
>  +  /* Construct an expression of a pointer to member.  */
>  +  tree datum;
>  +  if (is_ptrdatamem || is_ptrmemfunc)
>  +{
>  +  tree datum_type = TREE_VEC_ELT (arg_types, 0);
>  +
>  +  /* Dereference datum.  */
>  +  if (CLASS_TYPE_P (datum_type))
>  +  {
>  +bool is_refwrap = false;
>  +
>  +tree datum_decl = TYPE_NAME (TYPE_MAIN_VARIANT (datum_type));
>  +if (decl_in_std_namespace_p (datum_decl))
>  +  {
>  +tree name = DECL_NAME (datum_decl);
>  +if (name && (id_equal (name, "reference_wrapper")))
>  +  {
>  +/* Handle std::reference_wrapper.  */
>  +is_refwrap = true;
>  +datum_type = cp_build_reference_type (datum_type, false);
>
> Why do you change datum_type from std::reference_wrapper<...> to
> std::reference_wrapper<...>&?
>
>  +  }
>  +  }
>  +
>  +datum = build_trait_object (datum_type);
>  +
>  +/* If datum_type was not std::reference_wrapper, check if it has
>  +   operator*() overload.  If datum_type was std::reference_wrapper,
>  +   avoid dereferencing the datum twice.  */
>  +if (!is_refwrap)
>  +  if (get_class_binding (datum_type, get_identifier ("operator*")))
> >>>
> >>> We probably should

Re: [PATCH v23 32/33] c++: Implement __is_invocable built-in trait

2023-10-23 Thread Jason Merrill 

On 10/20/23 17:37, Patrick Palka wrote:

On Fri, 20 Oct 2023, Patrick Palka wrote:


On Fri, 20 Oct 2023, Patrick Palka wrote:


On Fri, 20 Oct 2023, Ken Matsui wrote:


This patch implements built-in trait for std::is_invocable.


Nice!  My email client unfortunately ate my first review attempt, so
apologies for my brevity this time around.


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.
(is_invocable_p): New function.
* method.h: New file to export build_trait_object in method.cc.


Given how much larger semantics.cc is than method.cc, maybe let's put 
is_invocable_p in method.cc instead?  And in general declarations can go 
in cp-tree.h.



diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 7cccbae5287..cc2e400531a 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -45,6 +45,10 @@ along with GCC; see the file COPYING3.  If not see
  #include "gomp-constants.h"
  #include "predict.h"
  #include "memmodel.h"
+#include "method.h"
+
+#include "print-tree.h"
+#include "tree-pretty-print.h"
  
  /* There routines provide a modular interface to perform many parsing

 operations.  They may therefore be used during actual parsing, or
@@ -11714,6 +11718,133 @@ classtype_has_nothrow_assign_or_copy_p (tree type, 
bool assign_p)
return saw_copy;
  }
  
+/* Return true if FN_TYPE is invocable with the given ARG_TYPES.  */

+
+static bool
+is_invocable_p (tree fn_type, tree arg_types)


(Sorry for the spam)  We'll eventually want to implement a built-in for
invoke_result, so perhaps we should preemptively factor out the bulk
of this function into a 'build_INVOKE' helper function that returns the
built tree?


+{
+  /* ARG_TYPES must be a TREE_VEC.  */
+  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);
+
+  /* std::is_invocable 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)
+/* A pointer to data member with non-one argument is not invocable.  */
+return false;
+
+  if (is_ptrmemfunc && TREE_VEC_LENGTH (arg_types) == 0)
+/* A pointer to member function with no arguments is not invocable.  */
+return false;
+
+  /* Construct an expression of a pointer to member.  */
+  tree datum;
+  if (is_ptrdatamem || is_ptrmemfunc)
+{
+  tree datum_type = TREE_VEC_ELT (arg_types, 0);
+
+  /* Dereference datum.  */
+  if (CLASS_TYPE_P (datum_type))
+   {
+ bool is_refwrap = false;
+
+ tree datum_decl = TYPE_NAME (TYPE_MAIN_VARIANT (datum_type));
+ if (decl_in_std_namespace_p (datum_decl))
+   {
+ tree name = DECL_NAME (datum_decl);
+ if (name && (id_equal (name, "reference_wrapper")))
+   {
+ /* Handle std::reference_wrapper.  */
+ is_refwrap = true;
+ datum_type = cp_build_reference_type (datum_type, false);


Why do you change datum_type from std::reference_wrapper<...> to 
std::reference_wrapper<...>&?



+   }
+   }
+
+ datum = build_trait_object (datum_type);
+
+ /* If datum_type was not std::reference_wrapper, check if it has
+operator*() overload.  If datum_type was std::reference_wrapper,
+avoid dereferencing the datum twice.  */
+ if (!is_refwrap)
+   if (get_class_binding (datum_type, get_identifier ("operator*")))


We probably should use lookup_member instead of get_class_binding since
IIUC the latter doesn't look into bases:

   struct A { int m; };
   struct B { A& operator*(): };
   struct C : B { };
   static_assert(std::is_invocable_v);

However, I notice that the specification of INVOKE
(https://eel.is/c++draft/func.require#lib:INVOKE) doesn't mention name
lookup at all so it strikes me as suspicious that we'd perform name
lookup here.


Agreed.  It seems that whether or not to build_x_indirect_ref should 
depend instead on whether f is a pointer to a member of decltype(t1) (as 
well as is_refwrap).



 I think this would misbehave for:

   struct A { };
   struct B : A { A& operator*() = delete; };

Re: [PATCH v23 32/33] c++: Implement __is_invocable built-in trait

2023-10-20 Thread Patrick Palka 
On Fri, 20 Oct 2023, Patrick Palka wrote:

> On Fri, 20 Oct 2023, Patrick Palka wrote:
> 
> > On Fri, 20 Oct 2023, Ken Matsui wrote:
> > 
> > > This patch implements built-in trait for std::is_invocable.
> > 
> > Nice!  My email client unfortunately ate my first review attempt, so
> > apologies for my brevity this time around.
> > 
> > > 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.
> > >   (is_invocable_p): New function.
> > >   * method.h: New file to export build_trait_object in method.cc.
> > > 
> > > 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 
> > > ---
> > >  gcc/cp/constraint.cc |   6 +
> > >  gcc/cp/cp-trait.def  |   1 +
> > >  gcc/cp/method.h  |  28 ++
> > >  gcc/cp/semantics.cc  | 135 +
> > >  gcc/testsuite/g++.dg/ext/has-builtin-1.C |   3 +
> > >  gcc/testsuite/g++.dg/ext/is_invocable1.C | 337 +++
> > >  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 +++
> > >  9 files changed, 733 insertions(+)
> > >  create mode 100644 gcc/cp/method.h
> > >  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 9fce36e12d1..29bf548d30a 100644
> > > --- a/gcc/cp/constraint.cc
> > > +++ b/gcc/cp/constraint.cc
> > > @@ -3754,6 +3754,12 @@ 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 05514a51c21..b8b7608c122 100644
> > > --- a/gcc/cp/cp-trait.def
> > > +++ b/gcc/cp/cp-trait.def
> > > @@ -71,6 +71,7 @@ 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/method.h b/gcc/cp/method.h
> > > new file mode 100644
> > > index 000..1aec8ec5cfd
> > > --- /dev/null
> > > +++ b/gcc/cp/method.h
> > > @@ -0,0 +1,28 @@
> > > +/* Functions exported by method.cc.
> > > +   Copyright (C) 2023 Free Software Foundation, Inc.
> > > +
> > > +This file is part of GCC.
> > > +
> > > +GCC is free software; you can redistribute it and/or modify
> > > +it under the terms of the GNU General Public License as published by
> > > +the Free Software Foundation; either version 3, or (at your option)
> > > +any later version.
> > > +
> > > +GCC is distributed in the hope that it will be useful,
> > > +but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > > +GNU General Public License for more details.
> > > +
> > > +You should have received a copy of the GNU General Public License
> > > +along with GCC; see the file COPYING3.  If not see
> > > +.  */
> > > +
> > > +#ifndef GCC_CP_METHOD_H
> > > +#define GCC_CP_METHOD_H 1
> > > +
> > > +#include "tree.h"
> > > +
> > > +/* In method.cc  */
> > > +extern tree build_trait_object (tree type);
> > 
> > Since other method.cc exports are already declared in cp-tree.h, for now
> > let's just declare this in cp-tree.h as well (under build_stub_object)
> > instead of creating a new header file.
> > 
> > > +
> > > +#endif  /* GCC_CP_METHOD_H  */
> > > diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> > > index 7cccbae5287..cc2e400531a 100644
> > > --- a/gcc/cp/semantics.cc
> > > +++ b/gcc/cp/semantics.cc
> > > @@ -45,6

Re: [PATCH v23 32/33] c++: Implement __is_invocable built-in trait

2023-10-20 Thread Patrick Palka 
On Fri, 20 Oct 2023, Patrick Palka wrote:

> On Fri, 20 Oct 2023, Ken Matsui wrote:
> 
> > This patch implements built-in trait for std::is_invocable.
> 
> Nice!  My email client unfortunately ate my first review attempt, so
> apologies for my brevity this time around.
> 
> > 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.
> > (is_invocable_p): New function.
> > * method.h: New file to export build_trait_object in method.cc.
> > 
> > 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 
> > ---
> >  gcc/cp/constraint.cc |   6 +
> >  gcc/cp/cp-trait.def  |   1 +
> >  gcc/cp/method.h  |  28 ++
> >  gcc/cp/semantics.cc  | 135 +
> >  gcc/testsuite/g++.dg/ext/has-builtin-1.C |   3 +
> >  gcc/testsuite/g++.dg/ext/is_invocable1.C | 337 +++
> >  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 +++
> >  9 files changed, 733 insertions(+)
> >  create mode 100644 gcc/cp/method.h
> >  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 9fce36e12d1..29bf548d30a 100644
> > --- a/gcc/cp/constraint.cc
> > +++ b/gcc/cp/constraint.cc
> > @@ -3754,6 +3754,12 @@ 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 05514a51c21..b8b7608c122 100644
> > --- a/gcc/cp/cp-trait.def
> > +++ b/gcc/cp/cp-trait.def
> > @@ -71,6 +71,7 @@ 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/method.h b/gcc/cp/method.h
> > new file mode 100644
> > index 000..1aec8ec5cfd
> > --- /dev/null
> > +++ b/gcc/cp/method.h
> > @@ -0,0 +1,28 @@
> > +/* Functions exported by method.cc.
> > +   Copyright (C) 2023 Free Software Foundation, Inc.
> > +
> > +This file is part of GCC.
> > +
> > +GCC is free software; you can redistribute it and/or modify
> > +it under the terms of the GNU General Public License as published by
> > +the Free Software Foundation; either version 3, or (at your option)
> > +any later version.
> > +
> > +GCC is distributed in the hope that it will be useful,
> > +but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > +GNU General Public License for more details.
> > +
> > +You should have received a copy of the GNU General Public License
> > +along with GCC; see the file COPYING3.  If not see
> > +.  */
> > +
> > +#ifndef GCC_CP_METHOD_H
> > +#define GCC_CP_METHOD_H 1
> > +
> > +#include "tree.h"
> > +
> > +/* In method.cc  */
> > +extern tree build_trait_object (tree type);
> 
> Since other method.cc exports are already declared in cp-tree.h, for now
> let's just declare this in cp-tree.h as well (under build_stub_object)
> instead of creating a new header file.
> 
> > +
> > +#endif  /* GCC_CP_METHOD_H  */
> > diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> > index 7cccbae5287..cc2e400531a 100644
> > --- a/gcc/cp/semantics.cc
> > +++ b/gcc/cp/semantics.cc
> > @@ -45,6 +45,10 @@ along with GCC; see the file COPYING3.  If not see
> >  #include "gomp-constants.h"
> >  #include "predict.h"
> >  #include "memmodel.h"
> > +#include "method.h"
> > +
> > +#include "print-tree.h"
> > +#include "tree-pretty-print.h"
> >  
> >  /*

Re: [PATCH v23 32/33] c++: Implement __is_invocable built-in trait

2023-10-20 Thread Patrick Palka 
On Fri, 20 Oct 2023, Ken Matsui wrote:

> This patch implements built-in trait for std::is_invocable.

Nice!  My email client unfortunately ate my first review attempt, so
apologies for my brevity this time around.

> 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.
>   (is_invocable_p): New function.
>   * method.h: New file to export build_trait_object in method.cc.
> 
> 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 
> ---
>  gcc/cp/constraint.cc |   6 +
>  gcc/cp/cp-trait.def  |   1 +
>  gcc/cp/method.h  |  28 ++
>  gcc/cp/semantics.cc  | 135 +
>  gcc/testsuite/g++.dg/ext/has-builtin-1.C |   3 +
>  gcc/testsuite/g++.dg/ext/is_invocable1.C | 337 +++
>  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 +++
>  9 files changed, 733 insertions(+)
>  create mode 100644 gcc/cp/method.h
>  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 9fce36e12d1..29bf548d30a 100644
> --- a/gcc/cp/constraint.cc
> +++ b/gcc/cp/constraint.cc
> @@ -3754,6 +3754,12 @@ 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 05514a51c21..b8b7608c122 100644
> --- a/gcc/cp/cp-trait.def
> +++ b/gcc/cp/cp-trait.def
> @@ -71,6 +71,7 @@ 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/method.h b/gcc/cp/method.h
> new file mode 100644
> index 000..1aec8ec5cfd
> --- /dev/null
> +++ b/gcc/cp/method.h
> @@ -0,0 +1,28 @@
> +/* Functions exported by method.cc.
> +   Copyright (C) 2023 Free Software Foundation, Inc.
> +
> +This file is part of GCC.
> +
> +GCC is free software; you can redistribute it and/or modify
> +it under the terms of the GNU General Public License as published by
> +the Free Software Foundation; either version 3, or (at your option)
> +any later version.
> +
> +GCC is distributed in the hope that it will be useful,
> +but WITHOUT ANY WARRANTY; without even the implied warranty of
> +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +GNU General Public License for more details.
> +
> +You should have received a copy of the GNU General Public License
> +along with GCC; see the file COPYING3.  If not see
> +.  */
> +
> +#ifndef GCC_CP_METHOD_H
> +#define GCC_CP_METHOD_H 1
> +
> +#include "tree.h"
> +
> +/* In method.cc  */
> +extern tree build_trait_object (tree type);

Since other method.cc exports are already declared in cp-tree.h, for now
let's just declare this in cp-tree.h as well (under build_stub_object)
instead of creating a new header file.

> +
> +#endif  /* GCC_CP_METHOD_H  */
> diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> index 7cccbae5287..cc2e400531a 100644
> --- a/gcc/cp/semantics.cc
> +++ b/gcc/cp/semantics.cc
> @@ -45,6 +45,10 @@ along with GCC; see the file COPYING3.  If not see
>  #include "gomp-constants.h"
>  #include "predict.h"
>  #include "memmodel.h"
> +#include "method.h"
> +
> +#include "print-tree.h"
> +#include "tree-pretty-print.h"
>  
>  /* There routines provide a modular interface to perform many parsing
> operations.  They may therefore be used during actual parsing, or
> @@ -11714,6 +11718,133 @@ classtype_has_nothrow_assign_or_copy_p (tree type, 
> bool assign_p)
>return saw_copy;
>  }
>  
> +/*