Multiple locations of duplicated definition for better user experience

[mununki]

The JSX internal representation and user both can define the props type in the same scope. In order to show a better error message, multiple locations of props type need to be handled specially. Even generalizing this issue, multiple locations of duplicated definitions could be handled for a better user experience.

[mununki]

module StringSet =
  Set.Make(struct type t = string let compare (x:t) y = String.compare x y end)

let check cl loc set_ref name =
  if StringSet.mem name !set_ref
  then raise(Error(loc, Env.empty, Repeated_name(cl, name)))
  else set_ref := StringSet.add name !set_ref

Isn't Set enough? Does it need to be changed map?

[cristianoc]

This is not specific to JSX, just motivated by it.

[Minnozz]

An easy solution may be to emit a separate warning with the other location. Although I believe warnings are never shown when there is an error?

Other languages often use hints attached to an error, where hints can have locations too ("Previous definition was here:")