E011: Something about this code breaks one of Turf's basic rules

This error covers a handful of specific rules that don’t really belong under any of Turf’s other, more specific errors. The exact message tells you which rule – here are the ones you’re most likely to actually run into:

You can’t call main yourself:

fn main(): int {    return 0;}main();   // not allowed -- main is your program's starting point, not a function you call

main runs automatically when your program starts. Calling it again from inside your own code doesn’t make sense, so Turf stops you.

You also can’t give main its own parameters:

fn main(x: int): int {   // not allowed    return 0;}

main always has the same fixed shape – no parameters, just fn main(): int. If you need input from outside your program, that comes through other means, not through main’s own parameter list.

If you’re using a compare/matches block, every pattern you match against has to be something Turf can figure out at compile time, like a plain number – not something computed while the program runs.

If you happen to see a message that starts with “Internal error”, that one’s different – it means the compiler itself hit a situation it wasn’t expecting, which is a bug in Turf, not a mistake in your code. It’s worth reporting rather than trying to work around.

For everything else under this error, the message itself tells you exactly which rule got broken – just follow what it says and you’ll be past it in no time.

Run turf --explain E011 in a terminal to read this again.