E149: That text can never be converted

What compiler error E149 means, and how to fix it.

to int, to double and to Enum convert a string while the program runs, and they panic when the text is not a number (or not a variant name). When the string is written right there in the code, Turf can tell in advance that the conversion would always panic, so it stops you now:

Example

enum Color { Red, Green }mut n: int = "abc" to int;          // "abc" is not an intmut d: double = "1.2.3" to double;  // two decimal pointsmut c: Color = "Purple" to Color;   // Color has no Purple

The whole string must be the value. to int takes an optional - and digits, in int’s range, so "12abc", " 12", "+5" and "1.5" are all rejected too. to double also takes one . and an exponent ("2.5", "1e3"), but not "inf" or "nan". A variant name must match exactly, including its case.

Usually the fix is to write the value itself instead of text:

Example

mut n: int = 42;mut d: double = 1.5;mut c: Color = Color::Green;

For text that comes from outside the program, such as input() or a file, use strings::parse_int or strings::parse_double, which return an error you can recover from instead of panicking.

Run turf --explain E149 in a terminal to read this again.