Make Binder's field private and clean up its usage

[tmandry]

AKA "tour de rustc"

Closes#49814.

[rust-highfive]

r? @petrochenkov

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

[tmandry]

r? @nikomatsakis

[rust-highfive]

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.

Resolving deltas: 100% (615842/615842), completed with 4901 local objects.
---
[00:00:42] configure: rust.quiet-tests := True
---
[00:31:59] error[E0423]: expected function, found struct `ty::Binder`
[00:31:59] --> librustdoc/clean/auto_trait.rs:289:26
[00:31:59] |
[00:31:59] 289 | let trait_pred = ty::Binder(trait_ref);
[00:31:59] | ^^^^^^^^^^ did you mean `ty::Binder { /* fields */ }`?
[00:31:59]
[00:31:59] error[E0423]: expected function, found struct `ty::Binder`
[00:31:59] --> librustdoc/clean/auto_trait.rs:625:30
[00:31:59] |
[00:31:59] 625 | predicates.push_back(ty::Binder(ty::TraitPredicate {
[00:31:59] | ^^^^^^^^^^ did you mean `ty::Binder { /* fields */ }`?
[00:31:59]
[00:31:59] error[E0532]: expected tuple struct/variant, found struct `ty::Binder`
[00:31:59] --> librustdoc/clean/mod.rs:2841:25
[00:31:59] |
[00:31:59] 2841 | for ty::Binder(ref pb) in obj.projection_bounds() {
[00:31:59] | ^^^^^^^^^^ did you mean `ty::Binder { /* fields */ }`?
[00:31:59]
[00:32:01] error[E0616]: field `0` of struct `rustc::ty::Binder` is private
[00:32:01] --> librustdoc/clean/mod.rs:123:9
[00:32:01] |
[00:32:01] 123 | self.0.clean(cx)
[00:32:01] | ^^^^^^
[00:32:01]
[00:32:04] error[E0616]: field `0` of struct `rustc::ty::Binder` is private
[00:32:04] --> librustdoc/clean/mod.rs:2849:42
[00:32:04] |
[00:32:04] 2849 | false, bindings, principal.0.substs);
[00:32:04] | ^^^^^^^^^^^
[00:32:04]
[00:32:05] error[E0616]: field `0` of struct `rustc::ty::Binder` is private
[00:32:05] --> librustdoc/clean/simplify.rs:157:16
[00:32:05] |
[00:32:05] 157 | if pred.0.trait_ref.self_ty().is_self() {
[00:32:05] | ^^^^^^
[00:32:05]
[00:32:05] thread 'main' panicked at 'no index for a field', libcore/option.rs:914:5
---
[00:32:06] Makefile:28: recipe for target 'all' failed
[00:32:06] make: *** [all] Error 1
travis_time:end:Tue, 17 Apr 2018 04:18:12 GMT
---
$ ls -lat $HOME/Library/Logs/DiagnosticReports/
ls: cannot access /home/travis/Library/Logs/DiagnosticReports/: No such file or directory

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)

[rust-highfive]

The job x86_64-gnu-llvm-3.9 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.

[00:53:19] ....i...................................................................................test [run-pass] run-pass/mir_heavy_promoted.rs has been running for over 60 seconds
[00:53:25] ............
[00:53:58] ....................................................................................................
[00:54:28] ......................................................................ii............................
[00:55:20] .................................i....................................................i.ii......test [run-pass] run-pass/saturating-float-casts.rs has been running for over 60 seconds
[00:56:05] ..............................................................................................iiiiii
[00:56:33] i...................................................................................................
[00:57:04] ....................................................................................................
[00:57:33] ....................................................................................................
---
[01:28:12] travis_fold:start:test_stage1-rustc_driver
travis_time:start:test_stage1-rustc_driver
Testing rustc_driver stage1 (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
[01:28:13] Compiling rustc_driver v0.0.0 (file:///checkout/src/librustc_driver)
[01:28:14] error[E0423]: expected function, found struct `ty::Binder`
[01:28:14] --> librustc_driver/test.rs:287:34
[01:28:14] |
[01:28:14] 287 | self.infcx.tcx.mk_fn_ptr(ty::Binder(self.infcx.tcx.mk_fn_sig(
[01:28:14] | ^^^^^^^^^^ did you mean `ty::Binder { /* fields */ }`?
[01:28:15] error: aborting due to previous error
[01:28:15] [01:28:15] For more information about this error, try `rustc --explain E0423`.
[01:28:15] error: Could not compile `rustc_driver`.
[01:28:15] error: Could not compile `rustc_driver`.
[01:28:15] [01:28:15] To learn more, run the command again with --verbose.
[01:28:15] [01:28:15] [01:28:15] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "test" "--target" "x86_64-unknown-linux-gnu" "--release" "--locked" "--color" "always" "--features" " jemalloc" "--manifest-path" "/checkout/src/rustc/Cargo.toml" "-p" "rustc_driver" "--" "--quiet"
[01:28:15] [01:28:15] [01:28:15] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test
[01:28:15] Build completed unsuccessfully in 0:44:18
[01:28:15] Build completed unsuccessfully in 0:44:18
[01:28:15] Makefile:58: recipe for target 'check' failed
[01:28:15] make: *** [check] Error 1
The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:002718f8
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)

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)

[tmandry]

@nikomatsakis:
While you're in the mindset of reviewing this PR, you might also want to take a look at this commit. I tried taking out the fns with FIXME(#20664), and they were only used in 4 places. I just can't tell which of those 4 is a valid use of skip_binder() and which are wrong :)

[bors]

☔ The latest upstream changes (presumably #49837) made this pull request unmergeable. Please resolve the merge conflicts.

[nikomatsakis]

@bors delegate=tmandry

r=me once rebased

[bors]

✌️ @tmandry can now approve this pull request

[tmandry]

@bors r+

[bors]

📌 Commit 9ffe9be has been approved by tmandry

[tmandry]

I think I got this wrong the first time..

@bors r=nikomatsakis

[bors]

💡 This pull request was already approved, no need to approve it again.

• There's another pull request that is currently being tested, blocking this pull request: Compile LLVM with Clang on release builders #50200

[bors]

📌 Commit 9ffe9be has been approved by nikomatsakis

[nikomatsakis]

@bors p=1 -- very prone to merge conflicts

[bors]

⌛ Testing commit 9ffe9be with merge c38733210bf533c5de0bcd369b5263488c4d95c4...

[bors]

💔 Test failed - status-travis

[kennytm]

@bors retry

The periodic outdated aws gem deployment error again.

[bors]

⌛ Testing commit 9ffe9be with merge 6eb4f1d...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing 6eb4f1d to master...