Merge 2018-11 LWG Motion 12

P1148R0 Cleaning up Clause 20

Fixes #2418

Author: zygoloid

source/iostreams.tex

@@ -162,6 +162,11 @@
 \indexlibrary{\idxcode{wsyncbuf}}%
 \indexlibrary{\idxcode{osyncstream}}%
 \indexlibrary{\idxcode{wosyncstream}}%
+\indexlibrary{\idxcode{fpos}}%
+\indexlibrary{\idxcode{streampos}}%
+\indexlibrary{\idxcode{wstreampos}}%
+\indexlibrary{\idxcode{u16streampos}}%
+\indexlibrary{\idxcode{u32streampos}}%
 \begin{codeblock}
 namespace std {
   template<class charT> class char_traits;
@@ -261,6 +266,8 @@
   using streampos  = fpos<char_traits<char>::state_type>;
   using wstreampos = fpos<char_traits<wchar_t>::state_type>;
   using u8streampos = fpos<char_traits<char8_t>::state_type>;
+  using u16streampos = fpos<char_traits<char16_t>::state_type>;
+  using u32streampos = fpos<char_traits<char32_t>::state_type>;
 }
 \end{codeblock}
 
@@ -303,9 +310,10 @@
 class template specialization
 \tcode{basic_streambuf<charT, traits>}
 serves as a base class for class templates
-\tcode{basic_stringbuf}
+\tcode{basic_stringbuf},
+\tcode{basic_filebuf},
 and
-\tcode{basic_filebuf}.
+\tcode{basic_syncbuf}.
 
 \pnum
 The
@@ -321,9 +329,10 @@
 class template specialization
 \tcode{basic_ostream<charT, traits>}
 serves as a base class for class templates
-\tcode{basic_ostringstream}
+\tcode{basic_ostringstream},
+\tcode{basic_ofstream},
 and
-\tcode{basic_ofstream}.
+\tcode{basic_osyncstream}.
 
 \pnum
 The
@@ -334,6 +343,15 @@
 and
 \tcode{basic_fstream}.
 
+\pnum
+\begin{note}
+For each of the class templates above,
+the program is ill-formed if
+\tcode{traits::char_type}
+is not the same type as
+\tcode{charT}\iref{char.traits}.
+\end{note}
+
 \pnum
 Other \grammarterm{typedef-name}{s} define instances of
 class templates
@@ -348,8 +366,7 @@
 \tcode{fpos}
 are
 used for specifying file position information.
-
-\pnum
+\begin{example}
 The types
 \tcode{streampos}
 and
@@ -359,6 +376,7 @@
 and
 \tcode{wchar_t}
 respectively.
+\end{example}
 
 \pnum
 \begin{note}
@@ -368,17 +386,6 @@
 \tcode{char_traits<char>}.
 An implementation can avoid this circularity by substituting equivalent
 types.
-One way to do this might be
-\begin{codeblock}
-template<class stateT> class fpos { @\commentellip@ };      // depends on nothing
-using _STATE = @\commentellip@ ;             // implementation private declaration of \tcode{stateT}
-
-using streampos = fpos<_STATE>;
-
-template<> struct char_traits<char> {
-  using pos_type = streampos;
-}
-\end{codeblock}
 \end{note}
 
 \rSec1[iostream.objects]{Standard iostream objects}