Fix Typst spacing after escaped expressions

src/Text/TeXMath/Writers/Typst.hs

@@ -44,17 +44,24 @@ writeExps = go . map writeExp
  where
    go (a : b : es)
     | Just (bstart, _) <- T.uncons b
-    , Just (astart, _) <- T.uncons a
     , Just (_, aend) <- T.unsnoc a
     , bstart == '\'' -- avoid space before a prime #239
-      || bstart == '|' || aend == '|' || bstart == '\\' || astart == '\\' -- #286
+      || bstart == '|' || aend == '|'
+      || bstart == '\\' || isStandaloneEscape a -- #291, #286
      = a <> go (b:es)
    go (a : as)
      = a <> if null as
                then mempty
                else " " <> go as
    go [] = mempty
 
+   -- A compound expression may start with an escape but end in an identifier.
+   -- Only a standalone escape suppresses the following space (#291).
+   isStandaloneEscape t =
+     case T.uncons t of
+       Just ('\\', rest) -> T.length rest == 1
+       _ -> False
+
 inParens :: Text -> Text
 inParens s = "(" <> s <> ")"
 

test/regression/291.test

@@ -0,0 +1,6 @@
+<<< tex
+)^n k \qquad
+(\mathbf x)^\top\mathbf A \qquad
+\mathcal G=\langle\mathcal N,(\mathcal A_i)_i,(u_i)_i\rangle
+>>> typst
+\)^n k #h(2em)\(upright(bold(x))\)^top upright(bold(A)) #h(2em) cal(G) = chevron.l cal(N)\,\(cal(A)_i\)_i\,\(u_i\)_i chevron.r