gdbsupport: Replace gdb::invoke_result with std::invoke_result

Given that GDB now requires C++17, we can replace gdb::invoke_result
with std::invoke_result which is provided by <type_traits>.

This patch also removes gdbsupport/invoke-result.h as it is not used
anymore.

Change-Id: I7e567356d38d6b3d85d8797d61cfc83f6f933f22

gdbsupport/filtered-iterator.h

@@ -19,7 +19,7 @@
 #ifndef COMMON_FILTERED_ITERATOR_H
 #define COMMON_FILTERED_ITERATOR_H
 
-#include "gdbsupport/invoke-result.h"
+#include <type_traits>
 
 /* A filtered iterator.  This wraps BaseIterator and automatically
    skips elements that FilterFunc filters out.  Requires that
@@ -56,7 +56,7 @@ public:
     : filtered_iterator (static_cast<const filtered_iterator &> (other))
   {}
 
-  typename gdb::invoke_result<decltype(&BaseIterator::operator*),
+  typename std::invoke_result<decltype(&BaseIterator::operator*),
 			      BaseIterator>::type
     operator* () const
   { return *m_it; }

gdbsupport/function-view.h

@@ -192,7 +192,7 @@
   You can find unit tests covering the whole API in
   unittests/function-view-selftests.c.  */
 
-#include "invoke-result.h"
+#include <type_traits>
 namespace gdb {
 
 namespace fv_detail {
@@ -230,7 +230,7 @@ class function_view<Res (Args...)>
   /* True if Func can be called with Args, and either the result is
      Res, convertible to Res or Res is void.  */
   template<typename Callable,
-	   typename Res2 = typename gdb::invoke_result<Callable &, Args...>::type>
+	   typename Res2 = typename std::invoke_result<Callable &, Args...>::type>
   struct IsCompatibleCallable : CompatibleReturnType<Res2, Res>
   {};
 

gdbsupport/invoke-result.h

@@ -1,37 +0,0 @@
-/* Compatibility wrapper around std::result_of and std::invoke_result.
-
-   Copyright (C) 2022-2023 Free Software Foundation, Inc.
-
-   This file is part of GDB.
-
-   This program 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 of the License, or
-   (at your option) any later version.
-
-   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.  */
-
-#ifndef GDBSUPPORT_INVOKE_RESULT_H
-#define GDBSUPPORT_INVOKE_RESULT_H
-
-#include <type_traits>
-
-namespace gdb
-{
-#if __cplusplus >= 201703L
-template<typename Callable, class... Args>
-using invoke_result = std::invoke_result<Callable, Args...>;
-#else
-template<typename Callable, typename... Args>
-using invoke_result = std::result_of<Callable (Args...)>;
-#endif
-
-} /* namespace gdb */
-
-#endif /* GDBSUPPORT_INVOKE_RESULT_H */

gdbsupport/parallel-for.h

@@ -22,7 +22,6 @@
 
 #include <algorithm>
 #include <type_traits>
-#include "gdbsupport/invoke-result.h"
 #include "gdbsupport/thread-pool.h"
 #include "gdbsupport/function-view.h"
 
@@ -145,14 +144,14 @@ private:
 
 template<class RandomIt, class RangeFunction>
 typename gdb::detail::par_for_accumulator<
-    typename gdb::invoke_result<RangeFunction, RandomIt, RandomIt>::type
+    typename std::invoke_result<RangeFunction, RandomIt, RandomIt>::type
   >::result_type
 parallel_for_each (unsigned n, RandomIt first, RandomIt last,
 		   RangeFunction callback,
 		   gdb::function_view<size_t(RandomIt)> task_size = nullptr)
 {
   using result_type
-    = typename gdb::invoke_result<RangeFunction, RandomIt, RandomIt>::type;
+    = typename std::invoke_result<RangeFunction, RandomIt, RandomIt>::type;
 
   /* If enabled, print debug info about how the work is distributed across
      the threads.  */
@@ -305,13 +304,13 @@ parallel_for_each (unsigned n, RandomIt first, RandomIt last,
 
 template<class RandomIt, class RangeFunction>
 typename gdb::detail::par_for_accumulator<
-    typename gdb::invoke_result<RangeFunction, RandomIt, RandomIt>::type
+    typename std::invoke_result<RangeFunction, RandomIt, RandomIt>::type
   >::result_type
 sequential_for_each (unsigned n, RandomIt first, RandomIt last,
 		     RangeFunction callback,
 		     gdb::function_view<size_t(RandomIt)> task_size = nullptr)
 {
-  using result_type = typename gdb::invoke_result<RangeFunction, RandomIt, RandomIt>::type;
+  using result_type = typename std::invoke_result<RangeFunction, RandomIt, RandomIt>::type;
 
   gdb::detail::par_for_accumulator<result_type> results (0);
 

gdbsupport/safe-iterator.h

@@ -19,7 +19,7 @@
 #ifndef COMMON_SAFE_ITERATOR_H
 #define COMMON_SAFE_ITERATOR_H
 
-#include "gdbsupport/invoke-result.h"
+#include <type_traits>
 
 /* A forward iterator that wraps Iterator, such that when iterating
    with iterator IT, it is possible to delete *IT without invalidating
@@ -77,7 +77,7 @@ public:
   basic_safe_iterator ()
   {}
 
-  typename gdb::invoke_result<decltype(&Iterator::operator*), Iterator>::type
+  typename std::invoke_result<decltype(&Iterator::operator*), Iterator>::type
     operator* () const
   { return *m_it; }