tidy script no longer checks lang features

[brson]

Here's a recent output. This script used to list all features in one place and now it only lists lib features.

[brson]

The problem is almost certainly that the script no longer detects the source file containing language features correctly. Update the script (src/tools/tidy/src/fetaures.rs) and add an assert that it found at least some lang feature to prevent this happening again.

[knight42]

@brson

The root of problem is that the status of lang features listed in src/tools/tidy/src/fetaures.rs were altered to lowercase in this commit, so the lines were all filtered out.

After a fix, the tidy check failed because of the following errors:

tidy check stage1 (x86_64-unknown-linux-gnu)
* 454 error codes
* highest error code: E0568
rust/src/libcore/fmt/mod.rs:1359: duplicating a lang feature
rust/src/libcore/fmt/mod.rs:1366: duplicating a lang feature
rust/src/libcore/cmp.rs:709: duplicating a lang feature
rust/src/libcore/cmp.rs:716: duplicating a lang feature
rust/src/libcore/cmp.rs:719: duplicating a lang feature
rust/src/libcore/cmp.rs:726: duplicating a lang feature
rust/src/libstd/macros.rs:287: duplicating a lang feature
thread 'main' panicked at 'some tidy checks failed', src/tools/tidy/src/main.rs:55

The feature never_type is used multiple times.

[knight42]

Perhaps we can put those implementations in a submodule?

[brson]

@knight42 Thanks for looking into this. Which implementations do you suggest putting into a submodule, and how will that get the script working again?

I think we can probably just rename the libs features that are violating the check.