E128: This variable needs a starting value

Some declarations can’t exist without a value. Turf found one that has none.

An immutable variable can never be assigned after it is created, so it has to get its one and only value right where it is declared:

immutable PI: double;             // never gets a value, and can't laterimmutable PI: double = 3.14159;

guess asks Turf to work out the type from the value, so it has nothing to work with if there isn’t one:

mut x: guess;                     // guess from what?mut x: guess = 5;                 // an int

Either give the variable its value, or – for a mut variable whose value comes later – say its type instead of using guess:

mut x: int;x = 5;

guess only works on a local variable that is given its value on the same line. A function’s parameters, its return type and a struct’s fields have no value to look at, so there you always write the type:

fn double_it(x: guess): int { ... }       // x: guess has nothing to infer fromfn double_it(x: int): int { ... }struct Counter { count: guess }           // so does a fieldstruct Counter { count: int }

Run turf --explain E128 in a terminal to read this again.