Merge 2019-02 LWG Motion 9

P1462R1 Mandating the Standard Library: Clause 20 - Strings library

Fixes #2700.

Author: zygoloid

source/strings.tex

@@ -224,9 +224,8 @@
 
 \begin{itemdescr}
 \pnum
-\requires
-\tcode{state_type}
-shall meet the
+\expects
+\tcode{state_type} meets the
 \oldconcept{Destructible} (\tref{destructible}),
 \oldconcept{CopyAssignable} (\tref{copyassignable}),
 \oldconcept{CopyConstructible} (\tref{copyconstructible}), and
@@ -2276,18 +2275,23 @@
 \end{itemdecl}
 
 \begin{itemdescr}
+\pnum
+\effects
+Inserts \tcode{n} copies of \tcode{c} before the character at position \tcode{pos}
+if \tcode{pos < size()},
+or otherwise at the end of the string.
+
+\pnum
+\returns
+\tcode{*this}
+
 \pnum
 \throws
 \begin{itemize}
 \item \tcode{out_of_range} if \tcode{pos > size()},
 \item \tcode{length_error} if \tcode{n > max_size() - size()}, or
 \item any exceptions thrown by \tcode{allocator_traits<Allocator>::allocate}.
 \end{itemize}
-\pnum
-\effects
-Inserts \tcode{n} copies of \tcode{c} before the character at position \tcode{pos}
-if \tcode{pos < size()},
-or otherwise at the end of the string.
 \end{itemdescr}
 
 \indexlibrarymember{insert}{basic_string}%
@@ -4092,10 +4096,6 @@
 \end{itemdecl}
 
 \begin{itemdescr}
-\pnum
-\effects
-Constructs an empty \tcode{basic_string_view}.
-
 \pnum
 \ensures
 \tcode{size_ == 0} and \tcode{data_ == nullptr}.