Handle type restrictions

[dbrgn]

The Gerber spec specifies a list of data types:

• Integers
• Decimals
• Coordinate Numbers
• Hexadecimal
• Names
• Strings

We should make sure that only valid values accrding to the spec can be passed in to types expecting these basic data types.

This means that we probably won't get around creating custom wrapper types.

Is there a way to create range types in Rust, e.g. a 32 bit signed integer >= 1? Or strings that only accept certain unicode codepoints? Ideally as much as possible at compile time.

@rnestler @dns2utf8

[dbrgn]

• Range types for integers (or refinement types?) rust-lang/rfcs#671
• https://www.reddit.com/r/rust/comments/3p1vgg/ranges_for_integer_data_types/

[dns2utf8]

we could test every function with:

fn validate_1_n(arg: i32) {
  assert!(arg > 1, "You shall not pass a number lower than 1");
}

Maybe extend it with https://github.com/alexcrichton/backtrace-rs to display nicer messages including the calling function.

[dbrgn]

If it happens at runtime, I'd rather go with something like TryFrom and return a Result.

[rnestler]

Yeah definitely go with Result for input parsing.