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.

datatype list a = Nil | Cons of a * list a

fun append (t ::: Type) (ls1 : list t) (ls2 : list t) : list t =
        case ls1 of
            Nil => ls2
          | Cons (h, t) => Cons (h, append t ls2)

(*val rec ones : list int = Cons (1, ones)*)
val rec ones = fn () => Cons (1, ones ())