Merge pull request JuliaLang#8803 from maleadt/pr_meta_docs

Update developer docs with push/popmeta! changes.

doc/devdocs/meta.rst

@@ -39,17 +39,19 @@ gets turned into an expression like this::
         end
     end
 
-``pushmeta!(ex, :symbol)`` appends ``:symbol`` to the end of the
-``:meta`` expression, creating a new ``:meta`` expression if
-necessary.
+``pushmeta!(ex, :symbol, args...)`` appends ``:symbol`` to the end of
+the ``:meta`` expression, creating a new ``:meta`` expression if
+necessary. If ``args`` is specified, a nested expression containing
+``:symbol`` and these arguments is appended instead, which can be used
+to specify additional information.
 
 To use the metadata, you have to parse these ``:meta`` expressions.
 If your implementation can be performed within Julia, ``popmeta!`` is
 very handy: ``popmeta!(body, :symbol)`` will scan a function *body*
 expression (one without the function signature) for a ``:meta``
-expression; if ``:symbol`` is present, it will return ``true`` and
-remove ``:symbol`` from the arguments of the ``:meta`` expression
-(deleting the expression altogether if there are no more arguments).
+expression, extract any arguments, and return a tuple ``(found::Bool,
+args::Array{Any})``. If the metadata did not have any arguments, or
+``:symbol`` was not found, the ``args`` array will be empty.
 
 Not yet provided is a convenient infrastructure for parsing ``:meta``
 expressions from C++.