Rename all mentions of nil to unit

[kenta7777]

Fixes#53719.

Renamed keywords nil to unit.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @davidtwco (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[rust-highfive]

⚠️Warning⚠️

• These commits modify submodules.

[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.

[00:02:04] extracting /checkout/obj/build/cache/2018-08-01/cargo-beta-x86_64-unknown-linux-gnu.tar.gz
[00:02:04] error: failed to resolve patches for `https://github.com/rust-lang-nursery/rust-clippy`
[00:02:04] [00:02:04] Caused by:
[00:02:04] patch for `clippy_lints` in `https://github.com/rust-lang-nursery/rust-clippy` did not resolve to any crates. If this is unexpected, you may wish to consult: https://github.com/rust-lang/cargo/issues/4678
[00:02:04] failed to run: /checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --manifest-path /checkout/src/bootstrap/Cargo.toml --locked
[00:02:04] make: *** [prepare] Error 1
[00:02:04] Makefile:81: recipe for target 'prepare' failed
[00:02:05] Command failed. Attempt 2/5:
[00:02:05] error: failed to resolve patches for `https://github.com/rust-lang/cargo`
[00:02:05] error: failed to resolve patches for `https://github.com/rust-lang/cargo`
[00:02:05] [00:02:05] Caused by:
[00:02:05] patch for `cargo` in `https://github.com/rust-lang/cargo` did not resolve to any crates. If this is unexpected, you may wish to consult: https://github.com/rust-lang/cargo/issues/4678
[00:02:05] failed to run: /checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --manifest-path /checkout/src/bootstrap/Cargo.toml --locked
[00:02:05] Makefile:81: recipe for target 'prepare' failed
[00:02:05] make: *** [prepare] Error 1
[00:02:07] Command failed. Attempt 3/5:
[00:02:07] error: failed to resolve patches for `https://github.com/rust-lang/cargo`
[00:02:07] error: failed to resolve patches for `https://github.com/rust-lang/cargo`
[00:02:07] [00:02:07] Caused by:
[00:02:07] patch for `cargo` in `https://github.com/rust-lang/cargo` did not resolve to any crates. If this is unexpected, you may wish to consult: https://github.com/rust-lang/cargo/issues/4678
[00:02:07] failed to run: /checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --manifest-path /checkout/src/bootstrap/Cargo.toml --locked
[00:02:07] make: *** [prepare] Error 1
[00:02:07] Makefile:81: recipe for target 'prepare' failed
[00:02:10] Command failed. Attempt 4/5:
[00:02:10] error: failed to resolve patches for `https://github.com/rust-lang/crates.io-index`
[00:02:10] error: failed to resolve patches for `https://github.com/rust-lang/crates.io-index`
[00:02:10] [00:02:10] Caused by:
[00:02:10] patch for `rustfmt-nightly` in `https://github.com/rust-lang/crates.io-index` did not resolve to any crates. If this is unexpected, you may wish to consult: https://github.com/rust-lang/cargo/issues/4678
[00:02:10] failed to run: /checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --manifest-path /checkout/src/bootstrap/Cargo.toml --locked
[00:02:10] make: *** [prepare] Error 1
[00:02:10] Makefile:81: recipe for target 'prepare' failed
[00:02:14] Command failed. Attempt 5/5:
[00:02:14] error: failed to resolve patches for `https://github.com/rust-lang/cargo`
[00:02:14] error: failed to resolve patches for `https://github.com/rust-lang/cargo`
[00:02:14] [00:02:14] Caused by:
[00:02:14] patch for `cargo` in `https://github.com/rust-lang/cargo` did not resolve to any crates. If this is unexpected, you may wish to consult: https://github.com/rust-lang/cargo/issues/4678
[00:02:14] failed to run: /checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --manifest-path /checkout/src/bootstrap/Cargo.toml --locked
[00:02:14] make: *** [prepare] Error 1
[00:02:14] Makefile:81: recipe for target 'prepare' failed
[00:02:14] The command has failed after 5 attempts.
travis_time:end:04ac2630:start=1536547046979439518,finish=1536547181764334898,duration=134784895380
---
travis_time:end:18ce3a66:start=1536547182265977098,finish=1536547182276325278,duration=10348180
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:221efcd1
$ 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:117736f0
travis_time:start:117736f0
$ 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:15902808
$ 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)

[kenta7777]

#53719

[scottmcm]

This seems to have a bunch of surprising submodule changes?

[davidtwco]

Thanks for the PR @kenta7777!

The change from nil to unit seems fine to me (cc @nikomatsakis) but like @scottmcm said, I'm not sure why there are submodule changes? - these seem unrelated to #53719.

[bors]

☔ The latest upstream changes (presumably #54011) made this pull request unmergeable. Please resolve the merge conflicts.

[kenta7777]

@davidtwco@scottmcm Thank you for your review and comment. I had changed the submodule code by mistake. I will fix and send pull request again.

[kenta7777]

I reverted my commits about changing submodule codes and committed mk_nil to mk_unit change only.

[davidtwco]

@kenta7777 This is looking really great. I've spotted a handful of other places in the compiler (such as those below) where there are still references to nil:

rust/src/librustc/ty/sty.rs

Lines 1461 to 1466 in 7f81604

	pubfnis_nil(&self) -> bool{
	matchself.sty{
	Tuple(ref tys) => tys.is_empty(),
	_ => false,
	}
	}

rust/src/libserialize/opaque.rs

Lines 57 to 60 in 7f81604

	#[inline]
	fnemit_nil(&mutself) -> EncodeResult{
	Ok(())
	}

If you could tackle these (and any remaining references to nil that I missed - perhaps run a grep) and maybe squash some of your commits down to one or two then that'd be great!

[kenta7777]

@davidtwco Thank you for your prompt response. I'll tackle with at least is_nil and emit_nil.

[nikomatsakis]

I think this seems fine — I agree that "nil" isn't really standard Rust terminology these days.

Nice job @davidtwco catching the missing cases.

[davidtwco]

Great work @kenta7777!

@bors r+

[bors]

📌 Commit 8134ee2 has been approved by davidtwco

[bors]

☔ The latest upstream changes (presumably #53873) made this pull request unmergeable. Please resolve the merge conflicts.

[davidtwco]

@kenta7777 Looks like you need to rebase this. Consider squashing to fewer commits when doing so. Once you do I'll take another look and re-approve.

[kenta7777]

@davidtwco I rebased this and resolved the merge conflicts.

[davidtwco]

@bors r+

[bors]

📌 Commit 26dbf56 has been approved by davidtwco

[kenta7777]

Thanks!