Implementing Into

[dtolnay]

Is there ever a case where Into should be implemented instead of From?

[dtolnay]

I found these in the standard library:

impl Into<Box<Path>> for PathBuf;
impl Into<Box<CStr>> for CString;
impl Into<Box<OsStr>> for OsString;

Is there some rule that makes it not possible to write these using From? Any other tradeoffs?

[dtolnay]

From rust-lang/rust#40009:

Currently, the opposite direction isn't doable with From (only Into) because of the separation between liballoc and libcollections. I'm holding off on those for a later PR.