Turf reads your code by following its structure: a bracket inside a bracket inside a bracket. To stay safe, it stops at a fixed depth instead of following forever, because input that nests without end can crash a compiler.
Example
mut x: int = ((((((((((((... hundreds of parentheses ...))))))))))));mut y: bool = !!!!!!!!!!!!!!!!!...;mut z: list<list<list<list<...>>>> ...;Real programs never get close to the limit, so when you see this it almost always means a bracket (or <, or !) was typed over and over by accident, or a closing one is missing and the count keeps growing. Check the line it points to for a repeated character and delete the extras.
If you genuinely have deeply nested data, give the inner pieces names with mut and build the result step by step.
Run turf --explain E111 in a terminal to read this again.