second round of refactorings for universes

[nikomatsakis]

A second round of (what I believe to be) "no functional change" refactorings, taken from my universes branch.

r? @scalexm

[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.

[00:04:11] travis_fold:start:tidy
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tidy check
[00:04:11] tidy error: /checkout/src/librustc_traits/dropck_outlives.rs:37: line longer than 100 chars
[00:04:11] tidy error: /checkout/src/librustc_traits/evaluate_obligation.rs:29: line longer than 100 chars
[00:04:11] tidy error: /checkout/src/librustc/infer/mod.rs:515: line longer than 100 chars
[00:04:12] some tidy checks failed
[00:04:12] [00:04:12] [00:04:12] 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"
[00:04:12] [00:04:12] [00:04:12] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
[00:04:12] Build completed unsuccessfully in 0:00:46
[00:04:12] Build completed unsuccessfully in 0:00:46
[00:04:12] make: *** [tidy] Error 1
[00:04:12] Makefile:79: recipe for target 'tidy' failed
The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
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$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
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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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[arielb1]

I'm not sure I prefer "superuniverse" to "subuniverse". Universes naturally form a tree, and the "subelement" relationship goes from a universe to its sub/superuniverse.

[nikomatsakis]

@arielb1

I'm not sure I prefer "superuniverse" to "subuniverse". Universes naturally form a tree, and the "subelement" relationship goes from a universe to its sub/superuniverse.

It seems like the use of "subuniverse" conflicts with methods like is_subset_of -- i.e., U0 is a "subset" of U1. Perhaps we can find some other terminology. I've found it pretty important when writing this code to have something that gives the right intuition.

Maybe "extension" and "extended" is a better terminology?

e.g.,

• create_subuniverse => create_extended_universe
• is_subset_of => is_extended_by

and so forth?

(For that matter, create_superuniverse should perhaps just be called create_universe or create_fresh_universe, with the "extension" aspect of it left to doc comments -- i.e., "creates a fresh universe that extends all previous universes")

[nikomatsakis]

Rebased and tidied. Went and tried the renaming I proposed. I wound up at a slightly different place, as you can see in the comment from the final commit:

---

remove the sub/super terminology for universes

Instead, we talk about:

• creating the "next" universe
• universes "extending" one another
• and u1.can_name(u2), meaning that u1 contains all names from u2

[nikomatsakis]

Now I am thinking create_child_universe might be better than "next" universe, to help build on the tree intuition. Unclear how much that matters though.

[scalexm]

@bors r+

[bors]

📌 Commit bae8a5ac3e5cbe85bade7f1313712fb8bc114a6d has been approved by scalexm

[Manishearth]

seems to be broken?

error: internal compiler error: librustc\infer\canonical\canonicalizer.rs:175: unexpected region in query response: `ReEarlyBound(0, 'i)`

in the rollup

https://ci.appveyor.com/project/rust-lang/rust/builds/19415197/job/kex1uawo1pxeg0ml

[bors]

☔ The latest upstream changes (presumably #54969) made this pull request unmergeable. Please resolve the merge conflicts.

[nikomatsakis]

@bors r=scalexm

[bors]

📌 Commit 5be9513ce4a6e593f5c50eab972de94ee8f60dd1 has been approved by scalexm

[bors]

⌛ Testing commit 5be9513ce4a6e593f5c50eab972de94ee8f60dd1 with merge 0e86b363814cfd66862f6df73bec3e5f63115b7c...

[bors]

💔 Test failed - status-appveyor

[nikomatsakis]

Whoops, I thought I had patched that problem.

[nikomatsakis]

@bors r=scalexm

[bors]

📌 Commit 05f67ca has been approved by scalexm

[bors]

⌛ Testing commit 05f67ca with merge 5a52983...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: scalexm
Pushing 5a52983 to master...