Pratt parsing with extra metadata

[catapillie]

Hello!
I've been using Pratt parsing for unary and binary operations, and it's been really useful. However I haven't found a way to propagate extra metadata when folding (similarly to how map_with, foldr_with and foldl_with work). I'd like to be able to fold the operations while retrieving the span of the currently parsed operation.

  a    *    1    +    -x
  ^         ^          ^     span of each atom
                      ^^     span of the negation
  ^^^^^^^^^^^                span of the product
  ^^^^^^^^^^^^^^^^^^^^^^     span of the sum

There doesn't seem to be a way to directly do this using pratt::prefix, pratt::postfix, etc... Is this currently not possible?
On 1.0.0-alpha.6. Thanks in advance!

[zesterer]

It's easier than you might think! You can simply add the span to the output type of the operator / atom like so:

atom.map_with(|x, e| (x, e.span())).pratt((
    infix(left(1), my_op.map_with(|x, e| (x, e.span())), |l, op, r, e| {
        // Note that in here, `l.1`, `op.1`, and `r.1` all give the span of their respective elements
        (Expr::MyOp(l, op, r), e.span())
    }),
))

[catapillie]

Thanks a lot!