message: Fix a few typos
  Summary: Fix a typo in a comment
diff: @@ -173,7 +173,7 @@ impl<V> ParametersSpec<V> {
  self.add(name, ParameterKind::Optional);
  }
  - /// Add an optional parameter. Will be the edefault value if the caller
  + /// Add an optional parameter. Will be the default value if the caller
  /// doesn't supply it. If you want to supply a position-only argument,
  /// prepend a `$` to the name.
  pub fn defaulted(&mut self, name: &str, val: V) {
  