[fs.op.funcs] Separate effects from returns. (#1848)

Author: jensmaurer

source/iostreams.tex

@@ -14956,13 +14956,15 @@
 \end{itemdecl}
 
 \begin{itemdescr}
+\pnum
+\effects
+If \tcode{exists(p)} is \tcode{false}, an error is reported\iref{fs.err.report}.
+
 \pnum
 \returns
 \begin{itemize}
 \item
-  If \tcode{exists(p)} is \tcode{false}, an error is reported\iref{fs.err.report}.
-\item
-  Otherwise, if \tcode{is_regular_file(p)}, the size in bytes of the file
+  If \tcode{is_regular_file(p)}, the size in bytes of the file
   \tcode{p} resolves to, determined as if by the value of the POSIX \tcode{stat}
   structure member \tcode{st_size} obtained as if by POSIX \tcode{stat()}.
 \item
@@ -15751,8 +15753,14 @@
 
 \begin{itemdescr}
 \pnum
-\returns An unspecified directory path suitable for temporary files. An error shall be reported if
-\tcode{exists(p)} is \tcode{false} or \tcode{is_directory(p)} is \tcode{false}, where \tcode{p} is the path to be returned.
+Let \tcode{p} be an unspecified directory path suitable for temporary files.
+
+\pnum
+\effects If \tcode{exists(p)} is \tcode{false} or \tcode{is_directory(p)} is
+  \tcode{false}, an error is reported\iref{fs.err.report}.
+
+\pnum
+\returns The path \tcode{p}.
   The signature with argument \tcode{ec} returns \tcode{path()} if an
   error occurs.