SIFR-PROTO-0005: Protocol receiver convention mismatch. - Sifr

SIFR-PROTO-0005 belongs to the Protocols diagnostic family. It means: protocol receiver convention mismatch.

Why It Happens

A value does not satisfy the structural protocol required by the operation, such as iteration, context management, or indexing.

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

Erroneous Code

class Readable(Protocol):
    def update(self) -> None:
        pass

class Counter:
    value: int

    def update(self) -> None:
        self.value += 1

How To Fix It

Declare a mutable receiver in the protocol when conforming implementations may mutate their receiver.

Fixed Code

class Updatable(Protocol):
    def update(mut self) -> None:
        pass

class Counter:
    value: int

    def update(self) -> None:
        self.value += 1

Details

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

See the Error Codes index for the complete catalog.