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.

fun f [r] [[Id, Foo] ~ r] (x : $(map (fn ts => $ts) r ++ [Id = int, Foo = string]))
    : $(map (fn ts => $ts) r ++ [Foo = string]) = x

val r = {}
val x : $(map (fn ts => $ts) _ ++ [Foo = string]) = f r