fix a problem with get_allocator

Author: dietmarkuehl

Makefile

@@ -2,7 +2,7 @@
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 SANITIZERS = release debug msan asan usan tsan
-.PHONY: default run update check ce todo distclean clean build test all $(SANITIZERS)
+.PHONY: default run update check ce todo distclean clean build test all format $(SANITIZERS)
 
 COMPILER=system
 CXX_BASE=$(CXX:$(dir $(CXX))%=%)
@@ -79,6 +79,9 @@ check:
 		< $$h sed -n "/^ *# *include <Beman\//s@.*[</]Beman/\(.*\).hpp>.*@$$from \1@p"; \
 	done | tsort > /dev/null
 
+format:
+	clang-format -i `git diff --name-only main | egrep '\.[ch]pp'`
+
 todo:
 	bin/mk-todo.py
 

include/beman/execution26/detail/get_allocator.hpp

@@ -19,7 +19,9 @@ struct get_allocator_t {
     auto operator()(Object&&) const =
         BEMAN_EXECUTION26_DELETE("the object requires a const query(get_allocator_t) overload");
     template <typename Object>
-        requires(not requires(const Object& object, const get_allocator_t& tag) { object.query(tag); })
+        requires(
+                    not requires(const Object& object, const get_allocator_t& tag) { object.query(tag); } &&
+                    not requires(Object&& object, const get_allocator_t& tag) { ::std::as_const(object).query(tag); })
     auto
     operator()(Object&&) const = BEMAN_EXECUTION26_DELETE("the object requires a query(get_allocator_t) overload");
     template <typename Object>
@@ -28,6 +30,7 @@ struct get_allocator_t {
                 })
     auto
     operator()(Object&&) const = BEMAN_EXECUTION26_DELETE("the query(get_allocator_t) overload needs to be noexcept");
+
     template <typename Object>
         requires(not requires(const Object& object, const get_allocator_t& tag) {
                     { object.query(tag) } noexcept -> ::beman::execution26::detail::simple_allocator<>;
@@ -36,7 +39,10 @@ struct get_allocator_t {
     operator()(Object&&) const = BEMAN_EXECUTION26_DELETE("the query(get_allocator_t) overload needs to be noexcept");
 
     template <typename Object>
-    auto operator()(Object&& object) const {
+        requires(requires(const Object& object, const get_allocator_t& tag) {
+            { object.query(tag) } noexcept -> ::beman::execution26::detail::simple_allocator<>;
+        })
+    auto operator()(Object&& object) const noexcept {
         return ::std::as_const(object).query(*this);
     }
 

include/beman/execution26/detail/simple_allocator.hpp

@@ -10,11 +10,13 @@
 // ----------------------------------------------------------------------------
 
 namespace beman::execution26::detail {
-template <typename Alloc = bool>
-concept simple_allocator = requires(Alloc alloc, ::std::size_t n) {
-    { *alloc.allocate(n) } -> ::std::same_as<typename Alloc::value_type&>;
-    alloc.deallocate(alloc.allocate(n), n);
-} && ::std::copy_constructible<Alloc> && ::std::equality_comparable<Alloc>;
+template <typename Alloc>
+concept simple_allocator =
+    requires(::std::remove_cvref_t<Alloc> alloc, ::std::size_t n) {
+        { *alloc.allocate(n) } -> ::std::same_as<typename ::std::remove_cvref_t<Alloc>::value_type&>;
+        alloc.deallocate(alloc.allocate(n), n);
+    } && ::std::copy_constructible<::std::remove_cvref_t<Alloc>> &&
+    ::std::equality_comparable<::std::remove_cvref_t<Alloc>>;
 } // namespace beman::execution26::detail
 
 // ----------------------------------------------------------------------------