Handle empty lists without annotations as parse errors

[sjakobi]

Here are a few samples of the parse errors:

⊢ []

Error: Invalid input

(input):2:1:
  |
2 | <empty line>
  | ^
Empty list literal without annotation

⊢ ([]) : T

Error: Invalid input

(input):1:4:
  |
1 | ([]) : T
  |    ^
Empty list literal without annotation

⊢ { c = [] }

Error: Invalid input

(input):1:10:
  |
1 | { c = [] }
  |          ^
Empty list literal without annotation

[sjakobi]

I'm still getting a doctest failure that I'm not sure how to fix:

/home/simon/src/dhall-haskell/dhall/src/Dhall/Tutorial.hs:452: failure in expression `input auto "[]" :: IO (Vector Natural)'
expected: "*** Exception:"
          "...Error...: Invalid input"
          "..."
          "(input):1:3:"
          "  |"
          "1 | []"
          "  |   ^"
          "Empty list literal without annotation"
 but got: "*** Exception: "
          "\ESC[1;31mError\ESC[0m: Invalid input"
          ""
          "(input):1:3:"
          "  |"
          "1 | []"
          "  |   ^"
          "Empty list literal without annotation"
          ""

Is there a good way to change the example so we don't get the escape codes?

[Gabriella439]

@sjakobi: The issue isn't the escape codes since those are handled by the ... in the sample doctest output. The problem is that (for some reason) parse errors have an additional space after the *** Exception: and the original type error did not.

[sjakobi]

@sjakobi: The issue isn't the escape codes since those are handled by the ... in the sample doctest output. The problem is that (for some reason) parse errors have an additional space after the *** Exception: and the original type error did not.

Oh! Interestingly, fixing that alone isn't sufficient. Apparently doctest can handle that trailing whitespace just fine.

The real problem was a missing line at the end of the output, which I fixed with

--- a/dhall/src/Dhall/Tutorial.hs
+++ b/dhall/src/Dhall/Tutorial.hs
@@ -458,6 +458,7 @@ import Dhall
 -- 1 | []
 --   |   ^
 -- Empty list literal without annotation
+-- ...
 --
 -- Also, list elements must all have the same type.  You will get an error if
 -- you try to store elements of different types in a list:

[sjakobi]

I was wondering whether we need to change anything about the MissingListType type error. It's probably still reachable in some way though, so I'll leave it there for now.