message: [move_prover] Give closure an explicit return type
  Closes:
  Approved by: dmitri-perelman
diff: @@ -459,7 +459,7 @@ impl Type {
  impl<'a> fmt::Display for TypeDisplay<'a> {
  fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
  use Type::*;
  - let comma_list = |f: &mut Formatter<'_>, ts: &[Type]| {
  + let comma_list = |f: &mut Formatter<'_>, ts: &[Type]| -> fmt::Result {
  let mut first = true;
  for t in ts {
  if first {
  