Make factorial take precedence over fraction in math expressions (#1487)

Fixes #1475.

src/syntax/parser.rs

@@ -307,6 +307,12 @@ fn math_expr_prec(p: &mut Parser, min_prec: usize, stop: SyntaxKind) {
     }
 
     while !p.eof() && !p.at(stop) {
+        if p.directly_at(SyntaxKind::Text) && p.current_text() == "!" {
+            p.eat();
+            p.wrap(m, SyntaxKind::Math);
+            continue;
+        }
+
         let Some((kind, stop, assoc, mut prec)) = math_op(p.current()) else {
             break;
         };

tests/typ/math/frac.typ

@@ -30,4 +30,5 @@ $ a_1/b_2, 1/f(x), zeta(x)/2, "foo"[|x|]/2 \
   1.2/3.7, 2.3^3.4 \
   🏳️‍🌈[x]/2, f [x]/2, phi [x]/2, 🏳️‍🌈 [x]/2 \
   +[x]/2, 1(x)/2, 2[x]/2 \
-  (a)b/2, b(a)[b]/2 $
+  (a)b/2, b(a)[b]/2 \
+  n!/2, 5!/2, n !/2, 1/n!, 1/5! $