tyenv_bug

[oshimayuki1124]

If you run programs below,

let f = fun x -> x;;
let f = fun x -> x f;;
f (fun x -> x) 4;;

ldti raise an error
Fatal error: exception Lambda_dti.Typing.Type_bug("failed to cast tyarg to ty")

This arose in CC.type_of_exp because fun x -> x f type in the second line is concidered under an environment which contain type information of the second f, not first one.
To fix this problem, I added some changes.

• typing.ml, typing.mli
  • omit tyenv from return values of ITGL.type_of_program
  • add type information into tyenv correctly in translate
• main.ml, test_examples.ml, stdlib.ml
  • follow the change about return values of ITGL.type_of_program
  • normalize tyenv and pass it to translate, CC.type_of_program
  • update tyenv with new_tyenv from translate
• test_typing.ml
  • follow the change about return values of ITGL.type_of_program

[ymyzk]

@oshimayuki1124 Thank you very much for your contribution! The change looks good to me. I'll merge the change once the CI pipeline succeeds.