Fix XML indentation in Emacs mode The return value of MATCH-STRING is a string. At least on Emacs 25, the comparisons between string and character with EQUAL could never succeed, and so the cases for matching braces were never triggered. GET-TEXT-PROPERTY may return a list rather than an atom (for example, on long lines with whitespace-mode turned on), and this broke the heuristic of looking for the tag face in previous text.

structure M : sig
    type t
    val x : t

    structure S : sig
        type u = t

        val eq : eq u
    end
end = struct
    type t = int
    val x = 0

    structure S = struct
        type u = t

        val eq = _
    end
end

val y = M.x = M.x