[WIP] Commenting out unsound specialization.

[pnkfelix]

If perf results indicate that we need this, then we should try to emulate it via a series of implementations on concrete types.

cc #67194

[rust-highfive]

r? @cramertj

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[pnkfelix]

@bors try
@rust-timer queue

[rust-timer]

Awaiting bors try build completion

[bors]

⌛ Trying commit f2e1357 with merge 4b018ef117d5404402ea68ca020e5409a10695f6...

[rust-highfive]

The job x86_64-gnu-llvm-7 of your PR failed (pretty log, 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.

2020-01-16T13:49:55.1897812Z ##[command]git remote add origin https://github.com/rust-lang/rust
2020-01-16T13:49:55.1979493Z ##[command]git config gc.auto 0
2020-01-16T13:49:55.2041307Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2020-01-16T13:49:55.2111391Z ##[command]git config --get-all http.proxy
2020-01-16T13:49:55.2255330Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/68280/merge:refs/remotes/pull/68280/merge
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---
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2020-01-16T14:59:05.0642435Z Check compiletest suite=codegen mode=codegen (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
2020-01-16T14:59:05.2640871Z 2020-01-16T14:59:05.2642151Z running 166 tests
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2020-01-16T14:59:13.5110444Z ---
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2020-01-16T14:59:34.0928476Z Check compiletest suite=debuginfo mode=debuginfo-gdb+lldb (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
2020-01-16T14:59:34.2825590Z 2020-01-16T14:59:34.2827260Z running 116 tests
2020-01-16T14:59:59.2586218Z .iiiii..i.....i..i...i..i.i.i..i..i..ii....i.i....ii..........iiii..........i.....i..i.......ii.i.ii 100/116
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2020-01-16T15:00:02.7138115Z 2020-01-16T15:00:02.7139951Z finished in 28.621
2020-01-16T15:00:02.7150406Z Uplifting stage1 rustc (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
2020-01-16T15:00:02.7150815Z Copying stage2 rustc from stage1 (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu / x86_64-unknown-linux-gnu)
---
2020-01-16T15:13:44.4641541Z iter::test_range_inclusive_exhaustion
2020-01-16T15:13:44.4641586Z 2020-01-16T15:13:44.4641627Z test result: FAILED. 996 passed; 1 failed; 2 ignored; 0 measured; 0 filtered out
2020-01-16T15:13:44.4641654Z 2020-01-16T15:13:44.4655884Z error: test failed, to rerun pass '-p core --test coretests'
2020-01-16T15:13:44.4681327Z 2020-01-16T15:13:44.4686067Z command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "test" "-Zconfig-profile" "--target" "x86_64-unknown-linux-gnu" "-Zbinary-dep-depinfo" "-j" "2" "--release" "--locked" "--color" "always" "--features" "panic-unwind backtrace compiler-builtins-c" "--manifest-path" "/checkout/src/libtest/Cargo.toml" "-p" "core" "--" "--quiet"
2020-01-16T15:13:44.4686244Z expected success, got: exit code: 101
2020-01-16T15:13:44.4686280Z ---
2020-01-16T15:13:44.4763103Z local time: Thu Jan 16 15:13:44 UTC 2020
2020-01-16T15:13:44.6495900Z network time: Thu, 16 Jan 2020 15:13:44 GMT
2020-01-16T15:13:44.6500582Z == end clock drift check ==
2020-01-16T15:13:45.0151558Z 2020-01-16T15:13:45.0266582Z ##[error]Bash exited with code '1'.
2020-01-16T15:13:45.0298736Z ##[section]Starting: Checkout
2020-01-16T15:13:45.0300266Z ==============================================================================
2020-01-16T15:13:45.0300332Z Task : Get sources
2020-01-16T15:13:45.0300374Z Description : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.

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]

☀️ Try build successful - checks-azure
Build commit: 4b018ef117d5404402ea68ca020e5409a10695f6 (4b018ef117d5404402ea68ca020e5409a10695f6)

[rust-timer]

Queued 4b018ef117d5404402ea68ca020e5409a10695f6 with parent 9fe05e9, future comparison URL.

[cramertj]

@bors r? @ghost

[rust-timer]

Finished benchmarking try commit 4b018ef117d5404402ea68ca020e5409a10695f6, comparison URL.

[nikomatsakis]

perf results look clean, at least, but maybe we should ping the original authors to see if they had particular cases in mind? I think @joshtriplett mentioned something about inclusive range performance being problematic, perhaps they remember.

[matthewjasper]

Test failure is legit. The specialization is being used for correct behaviour. I think that RangeInclusive is maintaining an invariant that should allow working around this, but I need to check the code carefully.

[joshtriplett]

On January 17, 2020 3:00:15 PM PST, Niko Matsakis ***@***.***> wrote: perf results look clean, at least, but maybe we should ping the original authors to see if they had particular cases in mind? I think @joshtriplett mentioned something about inclusive range performance being problematic, perhaps they remember.

If the perf results look good, I have no objections. Might want to check with the authors though.

[nikomatsakis]

@matthewjasper

Test failure is legit. The specialization is being used for correct behaviour. I think that RangeInclusive is maintaining an invariant that should allow working around this, but I need to check the code carefully.

Eep! I didn't look that closely at the code...

[pnkfelix]

Test failure is legit. The specialization is being used for correct behaviour. I think that RangeInclusive is maintaining an invariant that should allow working around this, but I need to check the code carefully.

I'll try to look into this during whatever down-time I have today.

[pnkfelix]

I discussed this with @alexcrichton today. They said the libs team would take charge on how to handle this PR and issue #67194

[pnkfelix]

(see also PR ##68358 )

[pnkfelix]

We do not need this anymore; PR #68835 resolved the unsoundness in question (by changing the representation of RangeInclusive so that we do not need to use the unsound specialization).