Remove Reflect

[est31]

PR for removing the Reflect trait. Opened so that a crater run can be done for testing the impact: #27749 (comment)

Fixes #27749

[rust-highfive]

r? @pnkfelix

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[est31]

I'm not 100% sure of the comment change in src/librustc/traits/select.rs (and generally I don't have much knowledge of the code involved, but the change seemed pretty straightforward). Correct me if I'm wrong.

[bors]

☔ The latest upstream changes (presumably #39071) made this pull request unmergeable. Please resolve the merge conflicts.

[est31]

Rebased.

[bors]

☔ The latest upstream changes (presumably #39243) made this pull request unmergeable. Please resolve the merge conflicts.

[est31]

@nikomatsakis you said that you've started a crater run on this PR. Are there any results in yet? Also, will me rebasing this PR in any way inconvenience the crater run? I don't want to force-push and destroy something :)

[nikomatsakis]

@est31 let me check :) also, rebase away

[nikomatsakis]

@est31 something went wrong with my run :(

[est31]

@nikomatsakis rebased.

[brson]

I will crater it.

[brson]

Crater says.

[pnkfelix]

the three root regressions reported by crater all are pretty obvious (each crate is importing Reflect and so the compiler complains).

[nikomatsakis]

@bors r+

[bors]

📌 Commit af46d69 has been approved by nikomatsakis

[nikomatsakis]

The feature is deprecated and removal is the plan, and the PR looks good; impact is minimal. So I gave r+!

[bors]

⌛ Testing commit af46d69 with merge 5158501...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing 5158501 to master...