Issue 52057 — inference variable

[nikomatsakis]

Break out the computation of universal region relations and do it during the typeck, where we can handle the resulting constraints that arise.

r? @pnkfelix

[nikomatsakis]

A note on naming: I want to rename universal_region to free_region (which was actually the name I used originally...) both because it's less awkward and because we have two kinds of universally quantified regions: free regions (lifetime parameters) and bound regions like the one in for<'a> fn(&'a u32). In particular, free regions appear free in the fn body, but bound regions do not.

I wound up not doing the rename in this PR though because it would conflict so badly with #52488

[rust-highfive]

The job x86_64-gnu-llvm-5.0 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.

Click to expand the log.

[00:03:26] travis_fold:start:tidy
travis_time:start:tidy
tidy check
[00:03:27] tidy error: /checkout/src/librustc_mir/borrow_check/nll/region_infer/mod.rs:911: line longer than 100 chars
[00:03:27] tidy error: /checkout/src/librustc_mir/borrow_check/nll/region_infer/mod.rs:918: line longer than 100 chars
[00:03:28] some tidy checks failed
[00:03:28] 
[00:03:28] 
[00:03:28] 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"
[00:03:28] 
[00:03:28] 
[00:03:28] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
[00:03:28] Build completed unsuccessfully in 0:00:43
[00:03:28] Build completed unsuccessfully in 0:00:43
[00:03:28] Makefile:79: recipe for target 'tidy' failed
[00:03:28] make: *** [tidy] Error 1

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:00bb3938
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
---
travis_time:end:0f3ef3d4:start=1532607911117991719,finish=1532607911123170053,duration=5178334
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:1510d9a6
$ 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 -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:075f869a
travis_time:start:075f869a
$ 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:12550024
$ 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 p=1 -- this is a major blocker for NLL + EP2 in terms of causing ICEs and errors

[emilyalbini]

Ping from triage @pnkfelix! This PR needs your review.

[pnkfelix]

I'll not block review on this, but I'm sort of surprised you went with a Vec<Ty> with special case info about the last element rather than a (Vec<Ty>, Ty) ...

[pnkfelix]

r=me

since there are conflicts and niko is on PTO, I might take a shot at resolving the conflicts myself

[pnkfelix]

conflicts! That's what you get for trying to opt into new features!

[pnkfelix]

@bors r+

[bors]

📌 Commit b9652ae has been approved by pnkfelix

[bors]

⌛ Testing commit b9652ae with merge cc408fb...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: pnkfelix
Pushing cc408fb to master...