provide various trait implementations for arrays up to 44 elements

[alex]

fixes #51192

[rust-highfive]

r? @aidanhs

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[alex]

(The bug has additional context and rationale for why this would be useful)

[rust-highfive]

The job x86_64-gnu-llvm-3.9 of 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.

[00:04:58] travis_fold:start:tidy
travis_time:start:tidy
tidy check
[00:04:58] tidy error: /checkout/src/libcore/array.rs:288: line longer than 100 chars
[00:04:59] some tidy checks failed
[00:04:59] 
[00:04:59] 
[00:04:59] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/tidy" "/checkout/src" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "--no-vendor" "--quiet"
[00:04:59] 
[00:04:59] 
[00:04:59] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
[00:04:59] Build completed unsuccessfully in 0:01:49
[00:04:59] Build completed unsuccessfully in 0:01:49
[00:04:59] make: *** [tidy] Error 1
[00:04:59] Makefile:79: recipe for target 'tidy' failed

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:152438ec
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)

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)

[TimNN]

cc @rust-lang/libs, This PR will probably need a decision from you.

[alexcrichton]

Historically the libs team has decided to not change what we have, although it's been awhile so we can revisit this decision during the next triage meeting as well.

[alexcrichton]

Ok the libs team discussed this yesterday and have reached the same conclusion as before, so I'm going to close this. Thanks regardless thoug hfor the PR @alex!