Apply P0663R0 PR for 321: Concepts that use type traits are inadverte…

…ntly subsuming them

Fixes #321.

concepts.tex

@@ -268,13 +268,13 @@
 \indexlibrary{\idxcode{Same}}%
 \begin{itemdecl}
 template <class T, class U>
-concept bool Same = @\seebelow@;
+concept bool Same = is_same<T, U>::value; // \seebelow
 \end{itemdecl}
 
 \begin{itemdescr}
 \pnum
-\tcode{Same<T, U>} is satisfied if and
-only if \tcode{T} and \tcode{U} denote the same type.
+There need not be any subsumption relationship between \tcode{Same<T, U>} and
+\tcode{is_same<T, U>::value}.
 
 \pnum
 \remarks For the purposes of constraint checking, \tcode{Same<T, U>} implies
@@ -309,7 +309,7 @@
 \begin{itemdecl}
 template <class T, class U>
 concept bool ConvertibleTo =
-  is_convertible<From, To>::value &&
+  is_convertible<From, To>::value && // \seebelow
   requires(From (&f)()) {
     static_cast<To>(f());
   };
@@ -444,18 +444,28 @@
 \indexlibrary{\idxcode{Integral}}%
 \begin{itemdecl}
 template <class T>
-concept bool Integral = is_integral<T>::value;
+concept bool Integral = is_integral<T>::value; // \seebelow
 \end{itemdecl}
 
+\begin{itemdescr}
+\pnum
+There need not be any subsumption relationship between \tcode{Integral<T>} and
+\tcode{is_integral<T>::value}.
+\end{itemdescr}
+
 \rSec2[concepts.lib.corelang.signedintegral]{Concept \tcode{SignedIntegral}}
 
 \indexlibrary{\idxcode{SignedIntegral}}%
 \begin{itemdecl}
 template <class T>
-concept bool SignedIntegral = Integral<T> && is_signed<T>::value;
+concept bool SignedIntegral = Integral<T> && is_signed<T>::value; // \seebelow
 \end{itemdecl}
 
 \begin{itemdescr}
+\pnum
+There need not be any subsumption relationship between \tcode{SignedIntegral<T>} and
+\tcode{is_signed<T>::value}.
+
 \pnum
 \enternote \tcode{SignedIntegral<T>} may be satisfied even for
 types that are not signed integral types~(\cxxref{basic.fundamental});