Triage ignored tests by given them reasons or fixing them

[klutzy]

Copying summary from jyn514's comment:

The header command ignore-test is used in a bunch of different tests:

; rg ignore-test tests | wc -l
65

We should

1. Categorize why the tests are ignored.
   • In particular, a lot have "not a test" comments, so they can be moved to auxiliary folders to avoid compiletest trying to build them.
2. Decide how to fix them. A lot have more specific issues associated with them and those you can probably just ignore. The rest will be on a case-by-case basis; you can ask on Zulip if you get stuck. I think all ignored tests should either have an associated issue or be removed all together.

[Sawyer47]

My idea is to add a way to specify why a test is ignored (causes ice, fails to compile, fails to run). Test runner could compile such tests and check whether they still compile / cause ice / fail to compile / fail to run and warn if the something changed.

[steveklabnik]

Triage: I'm not aware of any changes in this area.

[Mark-Simulacrum]

Attempted to triage ignored tests. Summary below, also filed #41629 to unignore or update the ignore statements on a few tests to indicate that they are auxiliary files.

Nightly-only:

• src/test/rustdoc/issue-27362.rs

Currently fail, undiagnosed reasons:

• src/test/codegen-units/item-collection/cross-crate-closures.rs
• src/test/codegen-units/item-collection/non-generic-closures.rs
• src/test/codegen-units/partitioning/methods-are-with-self-type.rs
• src/test/run-pass/issue-31702.rs

I don't even know what this tried to test, but I expect it's gone by now (delete?):

• src/test/parse-fail/regions-out-of-scope-slice.rs

This compile successfully, but it should fail:

• src/test/compile-fail/dead-code-closure-bang.rs

Test claims that it has different output on 32/64 bit (#23926):

• src/test/compile-fail/huge-array-simple.rs

Unsized enums aren't supported:

• src/test/compile-fail/issue-17025.rs

This does not appear to be a compile-fail test:

• src/test/compile-fail/macro-expanded-include/foo/mod.rs

This should be a UI-test, probably -- compile-fail can't test this I think:

• src/test/compile-fail/fully-qualified-type-name3.rs

No associated stderr file for undiagnosed reasons:

• src/test/ui/codemap_tests/two_files_data.rs

[pnkfelix]

I don't even know what this tried to test, but I expect it's gone by now (delete?):

* [ ]  `src/test/parse-fail/regions-out-of-scope-slice.rs`

I did some research into where this came from; wow was that a rabbit hole.

Here's the commit where that test came from: 2db4259#diff-d7743dac25dc59daac6583aab0dc1bb8

It has a lot of interesting stuff (beyond just the look back into very old Rust syntax), like a hard-coded blk region for the current block (!).

From its inception, it was tagged an "xfail-test" (as in, ignore-test). The reason for it being ignored, according to f8bd955#diff-884e9fc8b00b17708aa78ee7e6645c6b , is that "blk" wasn't supported in the front-end. (Though I think the type checker was still doing something special for it, as shown here :

rust/src/librustc/middle/typeck/check.rs

Line 580 in f8bd955

let blk_br = ty::br_named(special_idents::blk);

)

So, yeah, we should just kill that test.

[Mark-Simulacrum]

I've filed #71711 which further updates some things here and put an updated description of what's left as ignored tests in the issue description. I'm personally leaning towards closing this at this point as I think the remaining tests are sufficiently uninteresting to not be worth having a meta tracking issue like this for.