SIFR-PROTO-0002: Invalid iterator or reversible protocol signature. - Sifr

SIFR-PROTO-0002 belongs to the Protocols diagnostic family. It means: invalid iterator or reversible protocol signature.

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-0002 locally to see the renderer’s exact message template and any machine-applicable suggestions for the compiler version you are running.

Erroneous Code

for item in NotIterable():
    pass

How To Fix It

Implement the required protocol shape, or pass a value that already satisfies the iterator, context-manager, hashable, or comparable requirement.

Fixed Code

class Items:
    def __iter__(self) -> Iterator[int]:
        return iter([1, 2, 3])

for item in Items():
    pass

Details

Field	Value
Code	`SIFR-PROTO-0002`
Family	`PROTO`
Severity	Error
Stability	stable
Owner	`sifr_lowering::lower::classes`
Representative fixture	`crates/sifr/tests/e2e/fail/invalid_iter_signature.sifr`

See the Error Codes index for the complete catalog.