Explanation: Every element in the list must have a type matching the type
annotation at the end of the list

For example, this is a valid ❰List❱:


    ┌──────────────────────────┐
    │ [1, 2, 3] : List Integer │  Every element in this ❰List❱ is an ❰Integer❱
    └──────────────────────────┘


.. but this is $_NOT a valid ❰List❱:


    ┌──────────────────────────────┐
    │ [1, "ABC", 3] : List Integer │  The second element is not an ❰Integer❱
    └──────────────────────────────┘


Your ❰List❱ elements should have this type:

↳ $txt0

... but the following element at index $txt1:

↳ $txt2

... has this type instead:

↳ $txt3