Option and nullability

Informative guide. This Book page explains Beskid but does not define the standard. For normative requirements, use the Beskid Standard.

If you type null expecting sympathy, you will receive diagnostics instead.

Option<T> only

Optional presence must use Option<T> (corelib Core.Optional.Option) or an explicit enum with a dedicated absent variant at API boundaries.

• Forbidden: null, optional keyword, ?T sugar
• Present / absent: Option<T>::Some(x) / Option<T>::None (exact constructors per corelib)

Danger

Do not model failure as Option: use Result-shaped enums for errors (error handling).

Why the industry default is rejected

null made billion-dollar bugs feel normal. Beskid chooses explicit enums so absence shows up in match, not in a surprise NRE at runtime.

Handling options

Use match on options (see enums and match). Calling methods on a maybe-absent value without narrowing is a compile error, not a Friday production mystery.

classDiagram
accTitle: Option as an enumeration
accDescr: Option of T is an enumeration with the variants Some and None, and a match on it handles both.
class Option~T~ {
<<enumeration>>
Some(T)
None
}
class MatchExpression {
handles None as absent
handles Some as inner T
}
MatchExpression ..> Option : narrows

Text equivalent: Option<T> is an enumeration with variants Some(T) and None. A match narrows it, handling the absent case and using the inner T in the present case.

Normative decisions

• D-LM-TYP-002: Option<T> only in Types
• Glossary: glossary and conformance

Next

Functions and methods