Option and nullability

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

Option<T> only

Optional presence must use Option<T> (corelib Query.Contracts.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.

flowchart TD
  V[Value] --> M{match Option}
  M -->|None| H0[handle absent]
  M -->|Some| H1[use inner T]

Normative decisions

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

Next

Functions and methods