Add #![feature(alloc)], when enabling collections and/or alloc feature

[MathiasKoch]

error[E0658]: use of unstable library feature 'alloc': this library is unlikely to be stabilized in its current form or name (see issue #27783)
--> /home/mathias/.cargo/registry/src/github.com-1ecc6299db9ec823/core_io-0.1.20190427/src/lib.rs:15:51
|
15 | #[cfg(all(feature="collections",no_collections))] extern crate alloc as collections;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: add #![feature(alloc)] to the crate attributes to enable

[jethrogb]

Whoops, looks like this was accidentally broken in 81adf07

[jethrogb]

All these features need to be added back:

• alloc
• collections
• str_char
• unicode

@parasyte do you think you'd be able to fix this and #19?

[parasyte]

I wasn't able to build with those features enabled. :( rustc complained that they were unknown.

[jethrogb]

That's weird, the crate has #![allow(stable_features,unused_features)]

[parasyte]

I'll look at it when I get time this week.

[jethrogb]

Hmm I just tried it on nightly and indeed I can't use collections, str_char, unicode (alloc works though)

[jethrogb]

Behavior changed between:

• nightly-2018-08-06 73c78734b
• nightly-2018-08-14 d5a448b3f

[jethrogb]

Introduced in rust-lang/rust#52644

[jethrogb]

I guess we'll need to use the same version detection mechanism already in use for other features: https://github.com/jethrogb/rust-core_io/blob/master/build.rs#L52-L64

[parasyte]

Cool! I didn't even know that existed. Sounds good, I should be able to bisect where all of the features needed changes. (I had to add/remove features about 3 different times IIRC)

[MathiasKoch]

Any progress on this?

[parasyte]

I started on this. It's going to take some time because I need to rebuild the patches.