SIFR-OWN-0005: Immutable parameter is mutated. - Sifr

SIFR-OWN-0005 belongs to the Ownership and borrowing diagnostic family. It means: immutable parameter is mutated.

Why It Happens

The ownership model would be violated. Move values only once, keep borrows scoped, and cross task/channel/IPC boundaries only with owned values that satisfy the required safety traits.

Use sifr --explain SIFR-OWN-0005 locally to see the renderer’s exact message template and any machine-applicable suggestions for the compiler version you are running.

Erroneous Code

def consume(own values: list[int]) -> int:
    return len(values)

items: list[int] = [1, 2]
taken: int = consume(items)
count: int = len(items)

How To Fix It

Move ownership only after the last use, keep mutable borrows scoped, and send only owned sendable values across task or channel boundaries.

Fixed Code

def consume(own values: list[int]) -> int:
    return len(values)

items: list[int] = [1, 2]
count: int = len(items)
taken: int = consume(items)

Details

Field	Value
Code	`SIFR-OWN-0005`
Family	`OWN`
Severity	Error
Stability	stable
Owner	`sifr_lowering::lower`
Representative fixture	`crates/sifr/tests/e2e/fail/own_parameter_mutation_requires_mut.sifr`

See the Error Codes index for the complete catalog.