#Types

Model alternatives with enums and validate external values before treating them as domain data.

#Valid states

#Why

An enum prevents combinations of optional fields that no operation can handle meaningfully.

#Rules

• MUST use enums for closed alternatives and Option for meaningful absence. [review]

• MUST use Result for a failure with an explanation rather than overload Option. [review]

• MUST keep external deserialization separate from domain validation. [review]

• MUST use private fields or validated constructors when arbitrary construction would violate an invariant. [review]

• MUST use generics or impl Trait when static capability dispatch is sufficient. [review]

• MUST justify dynamic dispatch and heap allocation rather than select them by habit. [review]

• MAY use newtypes to distinguish values with the same underlying representation. [review]

[review]

The compiler checks enum and capability types. Validation tests establish invariants that types alone cannot express.

#Enforcement

The compiler checks enum and capability types. Validation tests establish invariants that types alone cannot express.