Into implementations should be changed to From

[clarfonthey]

Currently, libstd has:

impl Into<Vec<u8>> for String
impl Into<OsString> for PathBuf

And this seems inconsistent with the other collection implementations which all use From instead. It makes sense that these would be changed to From to allow use of from, and it doesn't seem like it'd be a breaking change at all.

[steveklabnik]

it doesn't seem like it'd be a breaking change at all.

Given that all From impls yield an Into impl, probably not, but I wonder what @rust-lang/libs has to say about why this was chosen.

[alexcrichton]

Seems reasonable to me! I believe Into doesn't imply From (but the other way around does). We should switch these for consistency.

[retep998]

From for the Vec<u8> options is suspicious because that operation can fail. From for OsString to PathBuf seems fine though.

[caipre]

@clarcharr : Did you mean to include a distinct third case? The first and third are both Into<Vec<u8>> for String.

[cuviper]

@retep998 I think you're reading those backwards. String can become Vec<u8> without fail (but not vice versa), so impl Into<Vec<u8>> for String would be changed to impl From<String> for Vec<u8>.

[clarfonthey]

@caipre I actually completely missed that. I just copied this from the docs, which seem to have duplicated the impl on the list? Not sure if that's a bug.

[retep998]

@cuviper Oh right, From<T> for U is still omni directional, it just allows you to do U::from() in addition to T::into(). In that case all those impls are fine by me.