<>| is accepted as empty union type

[hagl]

When reading through the dhall-haskell sources I found that an optional bar | is accepted after an empty union type (probably some left-over code from a refactoring):

Welcome to the Dhall v1.40.1 REPL! Type :help for more information.
⊢ <>|

<>

This is is not accepted by the dhall grammar or the standard implementation:

<>|
dhall: user error ((input):1:3:
  |
1 | <>|
  |   ^
unexpected '|'
expecting "!=", "&&", "++", "--", "//", "//\\", "/\", "::", "==", "===", "{-", "||", '#', '*', '+', '.', ':', '?', '∧', '≡', '⩓', '⫽', crlf newline, end of input, newline, space, or tab
)

[Gabriella439]

Nice catch! Thank you for fixing that 🙂