Result value design (`err(x)/ok(x)`)

[bvssvni]

Dyon uses a separate dynamic type for result values. The result type has two variants, err and ok. It has a lot of common with option value, but there are a few differences.

• err(x) creates an error with message x, using deep clone
• ok(x) creates a successful result with value x, using deep clone
• unwrap(x) unwraps a result type, when error prints error message plus ? trace messages
• unwrap_err(x) unwraps error message
• is_err(x) returns true if result is an error

For both result and option, the ? operator propagates the error (requires -> on function):

• x?, x.a?, x[0]?.b.c? etc.
• foo()? or following after any expression

When a the value is none() or err(x), the ? operator propagates the error. Returns from the function. A trace message is added to help debugging on unwrap, describing where the ? operation happened. some(x) is converted to ok(x).

This is designed for:

• Explicit decide whether to use result
• Check when mutating a variable that it is result
• Convenient for debugging
• Common way of handling errors