Function immutable

Creates an immutable deep clone.

Values are processed according to their type:

• Cloned and frozen: plain objects and arrays; nested structures are cloned recursively; accessor properties are preserved as read-only (getters only, setters removed)
• Returned as-is: atoms, that is primitives, functions, and non-plain objects (for example, Date, Map, Set, class instances, or objects with null prototype)

This function is idempotent at every depth: every cloned object and array is branded internally, so calling it again on a frozen clone, or on any nested member extracted from one, returns the same reference. Members reached through multiple paths, or extracted and re-nested into another structure, keep a stable identity. This makes it safe and efficient to use defensively.

The clone keeps the declared type of value, so a write is refused at run time rather than by the compiler: state the constraint with DeepReadonly where a holder is to be held to it at compile time.

Creates an immutable deep clone, validating against a type guard.

Values are processed according to their type:

• Cloned and frozen: plain objects and arrays; nested structures are cloned recursively; accessor properties are preserved as read-only (getters only, setters removed)
• Returned as-is: atoms, that is primitives, functions, and non-plain objects (for example, Date, Map, Set, class instances, or objects with null prototype)

Validates value against the guard before freezing:

• Plain objects and arrays: memoizes validation; subsequent calls with the same guard skip re-validation and return the same reference; calls with a different guard trigger revalidation and rebranding
• Other values: validated on every call

The guard brands only the top-level clone; nested members carry the default brand, so they remain stable under guard-less immutable calls while a guarded call on a nested member revalidates it.

The clone keeps the type the guard validates, so a write is refused at run time rather than by the compiler: state the constraint with DeepReadonly where a holder is to be held to it at compile time.