That bug was a symptom of a more general confusion between raw 
docstrings and formatted docstrings, which I attempted to fix in commit 
b2205626370071bc85dc07b043c833bc50c0baec with the attached patch.

As the patch mentions, I'm puzzled about the syntax ‘(` PAT)’ in the 
docstring, since lread.c says that syntax is obsolete and ‘format’ 
quotes the grave accent.  The attached patch causes C-h f to suggest the 
syntax ‘(\` PAT)’ which is "safer" in some sense, I suppose.  If it's 
intended that pcase usage omit the backslash, then I guess that ‘format’ 
and/or lread.c need to be updated accordingly.