NLL: Fix bug in associated constant type annotations.

[davidtwco]

Fixes #57280.

This PR reverses the variance used when relating types from the type
annotation of an associated constant - this matches the behaviour of the
lexical borrow checker and fixes a bug whereby matching a &'a str
against a &'static str would produce an error.

r? @nikomatsakis

[nikomatsakis]

@bors r+

[bors]

📌 Commit 4933793 has been approved by nikomatsakis

[bors]

⌛ Testing commit 4933793 with merge 355347541f176f38a81dc67b36bbdcb81d758b7c...

[bors]

💔 Test failed - status-travis

[rust-highfive]

The job arm-android 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.

[01:48:24] test vec::test_splice_unbounded ... ok
[01:48:24] test vec::test_split_at_mut ... ok
[01:48:24] test vec::test_split_off ... ok
[01:48:24] test vec::test_swap_remove_empty ... ok
[01:48:25] died due to signal 11
[01:48:25] 
[01:48:25] 
[01:48:25] 
[01:48:25] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "test" "--target" "arm-linux-androideabi" "-j" "4" "--release" "--locked" "--color" "always" "--features" "panic-unwind backtrace" "--manifest-path" "/checkout/src/libstd/Cargo.toml" "-p" "alloc" "--"
[01:48:25] 
[01:48:25] 
[01:48:25] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test --target arm-linux-androideabi
[01:48:25] Build completed unsuccessfully in 1:38:05
---
travis_time:end:27dfa8f8:start=1546807109913681851,finish=1546807109930439636,duration=16757785
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:0fdbd5db
$ ln -s . checkout && for CORE in obj/cores/core.*; do EXE=$(echo $CORE | sed 's|obj/cores/core\.[0-9]*\.!checkout!\(.*\)|\1|;y|!|/|'); if [ -f "$EXE" ]; then printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" "$CORE"; gdb --batch -q -c "$CORE" "$EXE" -iex 'set auto-load off' -iex 'dir src/' -iex 'set sysroot .' -ex bt -ex q; echo travis_fold":"end:crashlog; fi; done || true
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:04d4d9bc
travis_time:start:04d4d9bc
$ cat ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers || true
cat: ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers: No such file or directory
travis_fold:end:after_failure.5
travis_fold:start:after_failure.6
travis_time:start:0465b8f8
$ dmesg | grep -i kill

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)

[nikomatsakis]

@bors retry

[nikomatsakis]

cc @rust-lang/infra -- this failure looked unrelated to the PR:

[01:48:24] test vec::test_splice_unbounded ... ok
[01:48:24] test vec::test_split_at_mut ... ok
[01:48:24] test vec::test_split_off ... ok
[01:48:24] test vec::test_swap_remove_empty ... ok
[01:48:25] died due to signal 11

[pietroalbini]

cc #55861

[bors]

⌛ Testing commit 4933793 with merge 21ac19d...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing 21ac19d to master...