[check] Add check for library element order

Also mark for exclusion four places where the canonical order
cannot be established due to dependencies.

Author: jensmaurer

source/iostreams.tex

@@ -3983,7 +3983,7 @@
 int_type overflow(int_type c = traits::eof());
 \end{itemdecl}
 
-\begin{itemdescr}
+\begin{itemdescr}  % NOCHECK: order
 \pnum
 \effects
 Consumes some initial subsequence of the characters of the

source/utilities.tex

@@ -1961,7 +1961,7 @@
   constexpr tuple<CTypes...> tuple_cat(Tuples&&... tpls);
 \end{itemdecl}
 
-\begin{itemdescr}
+\begin{itemdescr}  % NOCHECK: order
 \pnum
 In the following paragraphs, let $\tcode{T}_i$ be the $i^\text{th}$ type in \tcode{Tuples},
 $\tcode{U}_i$ be \tcode{remove_reference_t<T$_i$>}, and $\tcode{tp}_i$ be the $i^\text{th}$
@@ -4658,7 +4658,7 @@
   variant_alternative_t<I, variant<Types...>>& emplace(Args&&... args);
 \end{itemdecl}
 
-\begin{itemdescr}
+\begin{itemdescr}  % NOCHECK: order
 \pnum
 \mandates
 $\tcode{I} < \tcode{sizeof...(Types)}$.
@@ -4699,7 +4699,7 @@
   variant_alternative_t<I, variant<Types...>>& emplace(initializer_list<U> il, Args&&... args);
 \end{itemdecl}
 
-\begin{itemdescr}
+\begin{itemdescr}  % NOCHECK: order
 \pnum
 \mandates
 $\tcode{I} < \tcode{sizeof...(Types)}$.

tools/check-source.sh

@@ -73,6 +73,10 @@ grep -ne '^\\\(constraints\|mandates\|expects\|effects\|sync\|ensures\|returns\|
 # Fixup: sed 's/^\\\(constraints\|mandates\|expects\|effects\|sync\|ensures\|returns\|throws\|complexity\|remarks\|errors\)\s*\(.\)/\\\1\n\2/'
 # Fixup: sed 's/^\\ //'
 
+# Order of library elements.
+../tools/element-order.awk *.tex |
+    fail 'incorrect ordering of library elements' || failed=1
+
 # Change marker in [diff] followed by stuff.
 grep -Hne '^\\\(change\|rationale\|effect\|difficulty\|howwide\)\s.\+$' compatibility.tex |
     fail "change marker in [diff] followed by stuff" || failed=1

tools/element-order.awk

@@ -0,0 +1,32 @@
+#!/usr/bin/awk -f
+
+BEGIN {
+    items = "constraints  mandates  expects  effects  sync  ensures  returns  throws  complexity  remarks  errors"
+    linematch = "^[\\\\](" items ")"
+    gsub(/  /, "|", linematch)
+    items = " " items
+    # print linematch
+}
+
+/^.begin{itemdescr}/ {
+    elements = ""
+    startline = FNR
+    check = 1
+    if (/% NOCHECK:.* order/) {
+	check = 0
+    }
+}
+
+/^.end{itemdescr}/ {
+    if (check && length(elements) > 0) {
+	regex = substr(elements, 2)
+	gsub(/ /, " .* ", regex)
+	if (items !~ regex) {
+	    printf "%s:%d-%d: bad element ordering: %s\n", FILENAME, startline, FNR, elements
+	}
+    }
+}
+
+match ($0, linematch) > 0 {
+    elements = elements " " substr($0, 2)
+}