`priv fn` in an `impl` does not create a private method. The following code compiles and runs without error, even though `shl_unit()` is marked `priv`: https://github.com/mozilla/rust/blob/e447521c1ca2dbead5b485ddc43060b282840817/src/libstd/bigint.rs#L452 ``` extern mod std; fn main() { std::bigint::BigUint::from_uint(2).shl_unit(3); } ``` This issue might be related to issue #3452.