[Xy-pic] problem with [@] in labels

[Richard Lewis]

Consider the following two matrices. (See also the thread starting
with Message-ID: <3f554cde at shknews01> on comp.text.tex)

\usepackage[dvips,all]{xy}

\xymatrix{ A & B \ar[dl]|*[@]{\labelstyle{foo}} \\ C & D}

\xymatrix{ A & B  \\ C\ar@{<-}[ur]|*[@]{\labelstyle{foo}} & D}

[@] is aligns the label with the direction of the arrow, which it does
correctly, but in the first case the `foo' is printed on top of the
arrow (the second case is correct, in that the arrow is broken to make
space for the `foo').  Is this a bug?

This happens in \xygraph too:

  \xygraph{!{0;<2cm,0pc>:<0pc,2cm>::0}%
    %%
    B [dl] C
    "B":|*[@][F.]{\labelstyle{foo}} "C"
    %%
    "B"[dd]
    %%
    b [dl] c
    %%
    "c":@{<-}|*[@][F.]{\labelstyle{foo}} "b"
  }