Reorganize borrow check diagnostic code

[mark-i-m]

Currently borrow checker diagnostics are split across many different modules in different places in the librustc_mir crate. This moves them all to a diagnostics module. This also reduces the nesting of the modules a bit (sooo much nesting).

I am also thinking of moving stuff out of the nll module since we only have one borrow checker now (:tada:), and maybe it even makes sense to split out all of this stuff to a librustc_borrow_check, but those are for the future. Feel free to ping me here or on zulip and let me know what you think...

cc @nikomatsakis @matthewjasper @eddyb

[rust-highfive]

r? @matthewjasper

(rust_highfive has picked a reviewer for you, use r? to override)

[mark-i-m]

I still need to fix up a bunch of imports... also, I'm not super happy about sprinkling pub (in crate::borrow_check) in front of the fields of RegionInferenceContext and other structs... thoughts?

[mark-i-m]

@matthewjasper Looks like this is ready for review.

I would like to take a crack at making region_errors/region_name not be implemented in RegionInferenceContext at some point in a followup so that we could clean up the pub(in crate::borrow_check) messes...

[mark-i-m]

Sorry, one more thing: this will probably conflict with #66679, so maybe wait for that to merge first?

[bors]

☔ The latest upstream changes (presumably #56231) made this pull request unmergeable. Please resolve the merge conflicts.

[eddyb]

I wouldn't mind src/librustc_borrowck (not librustc_borrow_check because both "rustc" and fully-spelled-out "check" seem a bit excessive, but that's just a stylistic prefer), but:
That's only if there is no dependency between the rest of librustc_mir and borrowck (in either direction), i.e. if they are two independent components that only happen to be colocated.

[matthewjasper]

Unfortunately there is a dependency until polonius is fully implemented.

[mark-i-m]

Sorry, forgetting the command right now, but this is S-blocked on #66679

I rebased over that PR...

[rust-highfive]

The job x86_64-gnu-llvm-6.0 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.

2019-11-29T17:14:39.2266114Z ##[command]git remote add origin https://github.com/rust-lang/rust
2019-11-29T17:14:39.2436067Z ##[command]git config gc.auto 0
2019-11-29T17:14:39.2513431Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2019-11-29T17:14:39.2570664Z ##[command]git config --get-all http.proxy
2019-11-29T17:14:39.2726656Z ##[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/66815/merge:refs/remotes/pull/66815/merge
---
2019-11-29T17:25:22.7964484Z    Compiling rustc_parse v0.0.0 (/checkout/src/librustc_parse)
2019-11-29T17:26:14.0298288Z    Compiling syntax_expand v0.0.0 (/checkout/src/libsyntax_expand)
2019-11-29T17:27:24.5926545Z    Compiling rustc_typeck v0.0.0 (/checkout/src/librustc_typeck)
2019-11-29T17:31:20.1358147Z    Compiling rustc_mir v0.0.0 (/checkout/src/librustc_mir)
2019-11-29T17:31:39.2546688Z error[E0451]: field `local_names` of struct `borrow_check::diagnostics::region_errors::ErrorReportingCtx` is private
2019-11-29T17:31:39.2552068Z    --> src/librustc_mir/borrow_check/diagnostics/region_name.rs:217:38
2019-11-29T17:31:39.2578345Z     |
2019-11-29T17:31:39.2579177Z 217 |             infcx, body, mir_def_id, local_names, upvars, ..
2019-11-29T17:31:39.2579891Z     |                                      ^^^^^^^^^^^ field `local_names` is private
2019-11-29T17:31:39.2580255Z 
2019-11-29T17:31:39.2612055Z error[E0451]: field `local_names` of struct `borrow_check::diagnostics::region_errors::ErrorReportingCtx` is private
2019-11-29T17:31:39.2612769Z    --> src/librustc_mir/borrow_check/diagnostics/outlives_suggestion.rs:129:13
2019-11-29T17:31:39.2614551Z 129 |             local_names: self.local_names,
2019-11-29T17:31:39.2614551Z 129 |             local_names: self.local_names,
2019-11-29T17:31:39.2618182Z     |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ field `local_names` is private
2019-11-29T17:31:39.4364634Z error: aborting due to 2 previous errors
2019-11-29T17:31:39.4368300Z 
2019-11-29T17:31:39.4378982Z For more information about this error, try `rustc --explain E0451`.
2019-11-29T17:31:39.5785312Z error: could not compile `rustc_mir`.
---
2019-11-29T17:34:00.3215546Z   local time: Fri Nov 29 17:34:00 UTC 2019
2019-11-29T17:34:00.4750238Z   network time: Fri, 29 Nov 2019 17:34:00 GMT
2019-11-29T17:34:00.4750986Z == end clock drift check ==
2019-11-29T17:34:03.3148608Z 
2019-11-29T17:34:03.3270181Z ##[error]Bash exited with code '1'.
2019-11-29T17:34:03.3302413Z ##[section]Starting: Checkout
2019-11-29T17:34:03.3304756Z ==============================================================================
2019-11-29T17:34:03.3304814Z Task         : Get sources
2019-11-29T17:34:03.3304895Z 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)

[mark-i-m]

@rustbot modify labels: +S-blocked +S-waiting-on-author -S-waiting-on-review

[mark-i-m]

@rustbot modify labels: +S-waiting-on-review -S-blocked

[bors]

☔ The latest upstream changes (presumably #64736) made this pull request unmergeable. Please resolve the merge conflicts.

[matthewjasper]

@bors r+

[bors]

📌 Commit 64925139b37086265ad4738a54c7a0ccfb5423b2 has been approved by matthewjasper

[mark-i-m]

@matthewjasper rebased

[Dylan-DPC-zz]

@bors r+

[bors]

📌 Commit b998e83 has been approved by Dylan-DPC

[bors]

⌛ Testing commit b998e83 with merge a0312c1...

[bors]

☀️ Test successful - checks-azure
Approved by: Dylan-DPC
Pushing a0312c1 to master...