UPLC is not able to parse data in complex constant

[nielstron]

What Git revision are you using?

aiken v1.0.21-alpha+b25e82e

What operating system are you using, and which version?

• [x] Linux / Ubuntu
• [ ] Linux / Other
• [ ] macOS
• [ ] Windows

Describe what the problem is?

The following program fails to parse in aiken

(program 1.0.0 (con (list (pair data data)) [((B #), (I 0))]))

Error:   × error at 1:51: expected one of ['a' ..= 'z' | 'A' ..= 'Z' | '0' ..= '9' | '_' | '\''], found 'Data' instead of expected type

What should be the expected behavior?

Should correctly parse.

[nielstron]

Further examples

(program 1.0.0 (con (list data) [(B #00)]))
(program 1.0.0 (con (pair data data) [(B #00), (I 0)]))
(program 1.0.0 (con (pair data data) ((B #00), (I 0))))

Meanwhile, the following parse

(program 1.0.0 (con data (B #)))
(program 1.0.0 (con data (I 0)))
(program 1.0.0 (con (pair data data) (B #00, I 0)))

It is not entirely clarified in https://github.com/input-output-hk/plutus/issues/4751#issuecomment-1538377273 since the examples kind of contradict the syntax definition in these cases - but I would argue that both surrounding by parentheses and not should be fine? Other than that one could also argue that the last presented line (B #00, I 0) is actually ambiguous - it could be either a pair of data or a data pair, which is unfortunately not equivalent (the latter only occuring in plutus maps)

[nielstron]

According to the uplc executable provided in newer releases of the plutus repo, the syntax implemented in aiken is the correct one. The python package has been adjusted accordingly.