message: Add tests for unbound variables
diff: @@ -4,6 +4,15 @@ mod ty_of {
  use super::*;
  use self::host::Type;
  + #[test]
  + fn var_unbound() {
  + let ctx = Context::new();
  + let src = "foo";
  + let expr = src.parse().unwrap();
  +
  + assert!(ty_of(&ctx, &expr).is_err());
  + }
  +
  #[test]
  fn const_int() {
  let ctx = Context::new();
  @@ -103,3 +112,16 @@ mod ty_of {
  assert_eq!(ty_of(&ctx, &expr), Ok(Type::bool()));
  }
  }
  +
  +mod kind_of {
  + use super::*;
  +
  + #[test]
  + fn var_unbound() {
  + let ctx = Context::new();
  + let src = "foo";
  + let ty = src.parse().unwrap();
  +
  + assert!(kind_of(&ctx, &ty).is_err());
  + }
  +}
  