tabulary incorrectly accounts for b and p columns

[davidcarlisle]

The following example shows tabulary is over-wide if p is used (but m works)

\documentclass{article}
\usepackage{tabulary}
\def\x{one two three four five six seven eight nine ten }
\def\xy{Red \x. Green \x\x. Blue\x. }
\def\xyz{\xy\xy}
\begin{document}

\noindent
\begin{tabulary}{\textwidth}{p{5cm}LL}
\xyz&\xyz&\xyz\\
1&2&3  
\end{tabulary}

\noindent
\begin{tabulary}{\textwidth}{m{5cm}LL}
\xyz&\xyz&\xyz\\
1&2&3  
\end{tabulary}
\end{document}

A user suggests

275c275
<   \ifnum\@chnum<4
---
 >   \ifnum\@chnum<6
369c369
<   \ifnum\@chnum<4
---
 >   \ifnum\@chnum<6

Which looks eminently plausible, although this code hasn't changed in any substantial way since last century...

Recording here. More analysis required on what the real intention was (although the current behaviour is clearly wrong)