test: do with optional ;

tests/lean/run/doNotation2.lean

@@ -0,0 +1,17 @@
+new_frontend
+
+def f (x : Nat) : IO Nat := do
+IO.println "hello world"
+let aux (y : Nat) (z : Nat) : IO Nat := do
+  IO.println "aux started"
+  IO.println ("y: " ++ toString y ++ ", z: " ++ toString z)
+  return x+y
+aux x
+  (x + 1) -- It is part of the application since it is indented
+aux x (x -- parentheses use `withoutPosition`
+-1)
+aux x x;
+  aux x
+ x
+
+#eval f 10