LWG4203 Constraints on get-state functions are incorrect

Author: burblebee

source/exec.tex

@@ -1279,6 +1279,8 @@
 the expression \tcode{\exposid{FWD-ENV}(env).query(q, as...)} is ill-formed
 if \tcode{forwarding_query(q)} is \tcode{false};
 otherwise, it is expression-equivalent to \tcode{env.query(q, as...)}.
+The type \tcode{\exposid{FWD-ENV-T}(Env)} is
+\tcode{decltype(\exposid{FWD-ENV}(declval<Env>()))}.
 
 \pnum
 For a query object \tcode{q} and \tcode{a} subexpression \tcode{v},
@@ -3009,7 +3011,7 @@
 is initialized with a callable object equivalent to the following lambda:
 \begin{codeblock}
 []<class Sndr, class Rcvr>(Sndr&& sndr, Rcvr& rcvr) noexcept(@\seebelow@)
-    requires @\libconcept{sender_in}@<@\exposid{child-type}@<Sndr>, env_of_t<Rcvr>> {
+    requires @\libconcept{sender_in}@<@\exposid{child-type}@<Sndr>, @\exposid{FWD-ENV-T}@(env_of_t<Rcvr>)> {
 
   auto& [_, sch, child] = sndr;
 
@@ -3039,7 +3041,7 @@
 \pnum
 Let \tcode{Sigs} be
 a pack of the arguments to the \tcode{completion_signatures} specialization
-named by \tcode{completion_signatures_of_t<\exposid{child-type}<Sndr>, env_of_t<Rcvr>>}.
+named by \tcode{completion_signatures_of_t<\exposid{child-type}<Sndr>, \exposid{FWD-ENV-T}(env_of_t<Rcvr>)>}.
 Let \exposid{as-tuple} be an alias template such that
 \tcode{\exposid{as-tuple}<Tag(Args...)>} denotes
 the type \tcode{\exposid{decayed-tuple}<Tag, Args...>}, and
@@ -3514,9 +3516,13 @@
 \item
 given a query object \tcode{q},
 the expression \tcode{e.query(q)} is expression-equivalent
-to \tcode{\exposid{env}.query(q)} if that expression is valid,
-otherwise \tcode{e.query(q)} is expression-equivalent
-to \tcode{get_env(\exposid{rcvr}).query(q)}.
+to \tcode{\exposid{env}.query(q)} if that expression is valid;
+otherwise,
+if the type of \tcode{q} satisfies \exposconcept{forwarding-query},
+\tcode{e.query(q)} is expression-equivalent
+to \tcode{get_env(\exposid{rcvr}).query(q)};
+otherwise,
+\tcode{e.query(q)} is ill-formed.
 \end{itemize}
 
 \pnum
@@ -3543,7 +3549,7 @@
 \pnum
 Let \tcode{Sigs} be a pack of the arguments
 to the \tcode{completion_signatures} specialization named by
-\tcode{completion_signatures_of_t<\exposid{child-type}<Sndr>, env_of_t<Rcvr>>}.
+\tcode{completion_signatures_of_t<\exposid{child-type}<Sndr>, \exposid{FWD-ENV-T}(env_of_t<Rcvr>)>}.
 Let \tcode{LetSigs} be a pack of those types in \tcode{Sigs}
 with a return type of \tcode{\exposid{decayed-typeof}<\exposid{set-cpo}>}.
 Let \exposid{as-tuple} be an alias template
@@ -4174,7 +4180,8 @@
 \tcode{e.query(get_stop_token)} is expression-equivalent to
 \tcode{state.\exposid{stop-src}.get_token()}, and
 \item
-given a query object \tcode{q} with type other than \cv{} \tcode{stop_token_t},
+given a query object \tcode{q} with type other than \cv{} \tcode{stop_token_t}
+and whose type satisfies \exposconceptx{forwarding-que\-ry}{forwarding-query},
 \tcode{e.query(q)} is expression-equivalent to \tcode{get_env(rcvr).query(q)}.
 \end{itemize}
 
@@ -4201,7 +4208,7 @@
 
 template<class Rcvr>
 struct @\exposid{make-state}@ {
-  template<@\exposconcept{max-1-sender-in}@<env_of_t<Rcvr>>... Sndrs>
+  template<@\exposconcept{max-1-sender-in}@<@\exposid{FWD-ENV-T}@(env_of_t<Rcvr>)>... Sndrs>
   auto operator()(auto, auto, Sndrs&&... sndrs) const {
     using values_tuple = @\seebelow@;
     using errors_variant = @\seebelow@;
@@ -4238,7 +4245,7 @@
 \pnum
 The alias \tcode{values_tuple} denotes the type
 \begin{codeblock}
-tuple<value_types_of_t<Sndrs, env_of_t<Rcvr>, @\exposid{decayed-tuple}@, optional>...>
+tuple<value_types_of_t<Sndrs, @\exposid{FWD-ENV-T}@(env_of_t<Rcvr>), @\exposid{decayed-tuple}@, optional>...>
 \end{codeblock}
 if that type is well-formed; otherwise, \tcode{tuple<>}.
 
@@ -4426,7 +4433,7 @@
 is initialized with a callable object equivalent to the following lambda:
 \begin{codeblock}
 []<class Sndr, class Rcvr>(Sndr&& sndr, Rcvr& rcvr) noexcept
-  -> type_identity<value_types_of_t<@\exposid{child-type}@<Sndr>, env_of_t<Rcvr>>> {
+  -> type_identity<value_types_of_t<@\exposid{child-type}@<Sndr>, @\exposid{FWD-ENV-T}@(env_of_t<Rcvr>)>> {
   return {};
 }
 \end{codeblock}
@@ -4471,14 +4478,14 @@
 \tcode{Env} is \tcode{decltype((env))}.
 If \tcode{\exposconcept{sender-for}<Sndr, stopped_as_optional_t>}
 is \tcode{false}, or
-if the type \tcode{\exposid{single-sender-value-type}<Sndr, Env>}
+if the type \tcode{\exposid{single-sender-value-type}<\linebreak{}\exposid{child-type}<Sndr>, \exposid{FWD-ENV-T}(Env)>}
 is ill-formed or \tcode{void},
-then the expression \tcode{stopped_as_optional.transform_sender(sndr, env)}
+then the expression \tcode{stopped_as_optional.\linebreak{}transform_sender(sndr, env)}
 is ill-formed;
 otherwise, it is equivalent to:
 \begin{codeblock}
 auto&& [_, _, child] = sndr;
-using V = @\exposid{single-sender-value-type}@<Sndr, Env>;
+using V = @\exposid{single-sender-value-type}@<@\exposid{child-type}@<Sndr>, @\exposid{FWD-ENV-T}@(Env)>;
 return let_stopped(
   then(std::forward_like<Sndr>(child),
        []<class... Ts>(Ts&&... ts) noexcept(is_nothrow_constructible_v<V, Ts...>) {