SI-3971 error message carat mispoints at curried methods.

I found it to be a general palliative to unwrap applies when reporting errors.
Point at the thing being applied, not at the opening paren of a possibly
distant argument list. This might be slightly less accurate in a few cases,
but it is vastly less inaccurate in most cases, so I think it is an easy
victory for the forces of clarity.

Thanks to retronym for figuring out why issuing a better error message broke
the compiler on non-erroneous compile runs. The changes to "treesInResult" are
the consequence.