Visit all attributes for feature collection

[varkor]

Previously feature attributes were just collected on item-like "things" as well as exported macros and crate attributes. This ignored some places feature attributes could be specified, such as on enum variants.

Fixes #53391.

[rust-highfive]

r? @nikomatsakis

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[nikomatsakis]

@bors r+

[bors]

📌 Commit 23d10ec has been approved by nikomatsakis

[nikomatsakis]

@varkor this is kind of a regression, I suppose?

[varkor]

@nikomatsakis: this change potentially permits more features than before (for example the future_atomic_orderings feature in #53391). It shouldn't disallow any that were previously allowed.

(I also imagine the current behaviour didn't miss many feature attributes, because most would have appeared in tests. future_atomic_orderings only didn't because it was deliberately perma-unstable.)

[nikomatsakis]

@varkor sorry, to be clear, what I meant is:

This PR is fixing a regression where we were previously getting errors about "unrecognized feature" when indeed the feature was legitimate?

In particular I was wondering if we want p=1

[varkor]

@nikomatsakis: oh, sorry, yes that is the case. p=1 seems reasonable.

@bors p=1

[bors]

⌛ Testing commit 23d10ec with merge f7d31968fb2cc3a847ae5a8034b350d3981be744...

[eddyb]

@bors retry (higher priory PR had a spurious failure)

[rust-highfive]

Your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

Cloning into 'rust-lang/rust'...
travis_time:end:0b30505b:start=1534453940520227768,finish=1534453945826607108,duration=5306379340
$ cd rust-lang/rust
$ git checkout -qf f7d31968fb2cc3a847ae5a8034b350d3981be744
fatal: reference is not a tree: f7d31968fb2cc3a847ae5a8034b350d3981be744
The command "git checkout -qf f7d31968fb2cc3a847ae5a8034b350d3981be744" failed and exited with 128 during .
Your build has been stopped.

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[bors]

⌛ Testing commit 23d10ec with merge 81ba448...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing 81ba448 to master...