make use of pointer::is_null

[tesuji]

r? @Mark-Simulacrum

[rust-highfive]

The job mingw-check of your PR failed (pretty log, 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.

2019-12-27T17:59:28.2907689Z ##[command]git remote add origin https://github.com/rust-lang/rust
2019-12-27T17:59:28.3105633Z ##[command]git config gc.auto 0
2019-12-27T17:59:28.3190420Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2019-12-27T17:59:28.3239923Z ##[command]git config --get-all http.proxy
2019-12-27T17:59:28.3384464Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/67666/merge:refs/remotes/pull/67666/merge
---
2019-12-27T18:05:10.7779295Z     Checking panic_unwind v0.0.0 (/checkout/src/libpanic_unwind)
2019-12-27T18:05:14.0589541Z error[E0614]: type `bool` cannot be dereferenced
2019-12-27T18:05:14.0590884Z    --> src/libstd/sys/unix/os.rs:483:38
2019-12-27T18:05:14.0591511Z     |
2019-12-27T18:05:14.0592172Z 483 |         while !environ.is_null() && !*environ.is_null() {
2019-12-27T18:05:14.0593172Z 
2019-12-27T18:05:14.1918123Z error: aborting due to previous error
2019-12-27T18:05:14.1919042Z 
2019-12-27T18:05:14.1919713Z For more information about this error, try `rustc --explain E0614`.
---
2019-12-27T18:05:14.2169836Z   local time: Fri Dec 27 18:05:14 UTC 2019
2019-12-27T18:05:14.5116008Z   network time: Fri, 27 Dec 2019 18:05:14 GMT
2019-12-27T18:05:14.5121499Z == end clock drift check ==
2019-12-27T18:05:22.6826003Z 
2019-12-27T18:05:22.6950794Z ##[error]Bash exited with code '1'.
2019-12-27T18:05:22.6983995Z ##[section]Starting: Checkout
2019-12-27T18:05:22.6986033Z ==============================================================================
2019-12-27T18:05:22.6986123Z Task         : Get sources
2019-12-27T18:05:22.6986176Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.

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)

[tesuji]

r? @Centril

[Centril]

r? @rkruppe

[dtolnay]

Thanks! This is great.

[dtolnay]

r? dtolnay
@bors r+

[bors]

📌 Commit ef74bc2 has been approved by dtolnay

[tesuji]

Removed unused ptr imports in hermit, vxworks and wasi.

[Dylan-DPC-zz]

@bors r-
(failed in rollup #68087)

[tesuji]

I pushed the new changes. Could be re-reviewed?

[dtolnay]

@bors r+

[bors]

📌 Commit cd9a73d has been approved by dtolnay

[bors]

☔ The latest upstream changes (presumably #68115) made this pull request unmergeable. Please resolve the merge conflicts.