Introduced hash valued location markers in the spec

docs/language/dart.sty

 \def\keyword#1{\textbf{#1}}
 \def\builtinId#1{\textbf{#1}}
 \def\comment#1{\textit{#1}}
 \def\capt#1{\rmfamily \caption{#1}}
 \newcommand{\cd}[1]{\textsf{#1}}
 \def\lt{$<$}
 \def\gt{$>$}
 \def\<{$\langle$}
 \def\>{$\rangle$}
 
@@ skipping 95 matching lines @@
 \newenvironment{dartCode}[1][!ht] {
 %  \begin{verbatim}[#1]
   \def\@programcr{\@addfield\strut}
   \let\\=\@programcr
   \relax\@vobeyspaces\obeylines
 
   \sffamily
 }{
   %\end{verbatim}
 }
+
+
+% ----------------------------------------------------------------------
+% Support for hash valued Location Markers
+
+% very small font, to enable 33 char hash values in the margin
+\makeatletter
+\ifcase \@ptsize \relax% 10pt
+  \newcommand{\miniscule}{\@setfontsize\miniscule{2}{3}}% \tiny: 5/6
+\or% 11pt
+  \newcommand{\miniscule}{\@setfontsize\miniscule{3}{4}}% \tiny: 6/7
+\or% 12pt
+  \newcommand{\miniscule}{\@setfontsize\miniscule{3}{4}}% \tiny: 6/7
+\fi
+\makeatother
+
+% white: location markers should not create visual noise
+\definecolor{LMdim}{gray}{1.0}
+
+% insert location marker showing hash value of following paragraph
+\newcommand{\LMHash}[1]{%
+  \hspace{0pt}\marginpar{\raisebox{0.5ex}{\miniscule{\color{LMdim}#1}}}}
+
+% support convenient renewcommand
+\let\OriginalLMHash\LMHash
+
+% define a label, and show the associated logical location marker
+\newcommand{\LMLabel}[1]{%
+  \vspace{-\baselineskip}\hspace{0pt}\OriginalLMHash{\raisebox{10ex}{sec:#1}}%
+  \label{#1}}
+
+% dummy version of LMHash, always shows the same arbitrary hash value
+\renewcommand{\LMHash}[1]{\OriginalLMHash{ba01b04d58c8c4e259764498f823cc65}}
+
+% ----------------------------------------------------------------------
+