message: Construct SimpleStmt a bit more cleanly
  Summary: Use once instead of creating a vec first.
diff: @@ -132,8 +132,7 @@ SimpleStmt<S>: AstStmt =
  if v.is_empty() {
  e
  } else {
  - Stmt::Statements(
  - vec![e].into_iter().chain(v.into_iter()).collect())
  + Stmt::Statements(std::iter::once(e).chain(v).collect())
  .ast(l, r)
  }
  };
  