E072: A number can't start or end with an underscore

Turf lets you use _ inside a numeric literal to make long numbers easier to read, the same way you might write “1,000,000” by hand:

mut population: int = 1_000_000;mut pi_ish: double = 3.14_159;mut big_hex: int = 0xFF_FF_FF_FF;

The underscore only makes sense as a separator BETWEEN two digits. Put one at the very start or the very end of a run of digits, and there’s nothing for it to actually separate:

mut a: int = _5;     // ERROR: leading underscoremut b: int = 5_;     // ERROR: trailing underscoremut c: int = 0x_FF;  // ERROR: leading underscore right after the prefix

The fix is simply to remove the stray underscore:

mut a: int = 5;mut b: int = 5;mut c: int = 0xFF;

If you were trying to group digits, make sure every underscore has a real digit immediately on both sides of it.

Run turf --explain E072 in a terminal to read this again.