Support impl Trait in inlined documentation

[sinkuu]

impl Trait in argument position was not properly rendered when inlined from other crates. (a live example on docs.rs)

↓

[rust-highfive]

The job x86_64-gnu-llvm-6.0 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.

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travis_time:end:0efa6ae3:start=1559894987881585530,finish=1559894988615283313,duration=733697783
$ git checkout -qf FETCH_HEAD
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Encrypted environment variables have been removed for security reasons.
See https://docs.travis-ci.com/user/pull-requests/#pull-requests-and-security-restrictions
$ export SCCACHE_BUCKET=rust-lang-ci-sccache2
$ export SCCACHE_REGION=us-west-1
$ export GCP_CACHE_BUCKET=rust-lang-ci-cache
$ export AWS_ACCESS_KEY_ID=AKIA46X5W6CZEJZ6XT55
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[00:04:17] travis_fold:start:tidy
travis_time:start:tidy
tidy check
[00:04:18] tidy error: /checkout/src/librustdoc/clean/mod.rs:1702: line longer than 100 chars
[00:04:22] some tidy checks failed
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[00:04:22] 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"
[00:04:22] 
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[00:04:22] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
[00:04:22] Build completed unsuccessfully in 0:01:11
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travis_time:end:01252620:start=1559895263298385339,finish=1559895263303144686,duration=4759347
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$ 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
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$ 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
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$ 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)

[bors]

☔ The latest upstream changes (presumably #60293) made this pull request unmergeable. Please resolve the merge conflicts.

[ollie27]

Sorry for the late review.

Even with the (i as u32) -> param.index change I suggested there is still a problem with things like pub fn h(_x: impl Iterator<Item = u8>) {}, they render as:

The issue is that rustdoc uses simplify::where_clauses to convert the equality predicates into type bindings so that needs to be run before moving where predicates that are actually part of impl traits into cx.impl_trait_bounds. We could leave fixing this to a follow up PR though.

[ollie27]

Looks good, thanks!

@bors r+

[bors]

📌 Commit ea3e804 has been approved by ollie27

[bors]

⌛ Testing commit ea3e804 with merge 0ab453ada4ea66b0902b62d5db1648c0c9e0c69e...

[Centril]

Failed in #62509 (comment), @bors r-

[Centril]

@bors retry

[sinkuu]

I guess test failure on one platform was caused by indeterminism of HashMap iteration, so I changed it to use BTreeMap (param-index order should be ok).
Also a drive-by fix for ICE with impl Trait in type bounds.

[sinkuu]

@ollie27 Could you re-approve?

[bors]

☔ The latest upstream changes (presumably #63471) made this pull request unmergeable. Please resolve the merge conflicts.

[JohnCSimon]

Ping from triage
@sinkuu - can you please fix the merge conflict so that @ollie27 can re-review?
Thank you.

[sinkuu]

Rebased.

[ollie27]

Let's give this another go.

@bors r+

[bors]

📌 Commit 1fe6160 has been approved by ollie27

[bors]

⌛ Testing commit 1fe6160 with merge 521d784...

[bors]

☀️ Test successful - checks-azure
Approved by: ollie27
Pushing 521d784 to master...