Ownership Safety — E0030–E0035

Mojo-inspired ownership analysis. See Mojo-Style Safety for full documentation.

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BSK-E0030 — Mutation of Borrowed parameter

A Borrowed parameter (read-only reference) is mutated.

from typing import Annotated
from basilisk import Borrowed

def summarise(items: Annotated[list[int], Borrowed]) -> int:
    items.append(99)  # Error — cannot mutate Borrowed
    return sum(items)

BSK-E0031 — Use after ownership transfer

A value is used after its ownership has been transferred to another binding or function.

from typing import Annotated
from basilisk import Owned

def consume(data: Annotated[list[int], Owned]) -> int:
    return sum(data)

items = [1, 2, 3]
total = consume(items)
items.append(4)  # Error — items was moved into consume()

BSK-E0032 — Implicit copy of large structure

A large structure (over the configured size threshold) is implicitly copied. Requires explicit .copy() or Owned transfer.

BSK-E0033 — Missing ownership annotation (warning promoted to error)

A function parameter that receives a mutable type has no ownership annotation. Basilisk cannot determine the intended contract.

BSK-E0034 — Owned value not consumed or returned

An Owned value is created but neither consumed nor returned, leaking the resource.

BSK-E0035 — Multiple mutable references

Two InOut references to the same value exist simultaneously.