rustdoc: separate test collection from the main "clean"-ing pipeline.

[eddyb]

While reusing the documentation "clean"-ing infrastructure for collecting code examples to test may have seemed appealing at some point, doing the same through a HIR visitor is barely any harder.
At the same time, supporting both "regular documentation" and "test collection" modes in rustdoc::clean has its cost, requiring any use of a TyCtxt to be speculative, and provide some sort of fallback.

This simplification is the first step towards bringing rustdoc closer to the compiler, and perhaps even unifying the "local crate" (based on the HIR AST) and "inlinined across crates" (based on crate metadata and typesystem information) implementations of rustdoc.

Sadly, not all possible changes to rustdoc will be uncontroversial, so I'm starting small with this patch.

[rust-highfive]

r? @steveklabnik

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

[eddyb]

cc @GuillaumeGomez

[GuillaumeGomez]

Huge 👍 !

[eddyb]

r? @nrc cc @rust-lang/tools

[alexcrichton]

Sounds like a good change to me, there's tons of technical debt in rustdoc to be shed at this point

[nrc]

@bors: r+

[bors]

📌 Commit 60aa513 has been approved by nrc

[bors]

⌛ Testing commit 60aa513 with merge 5940fe3...

[bors]

💔 Test failed - auto-win-msvc-64-cargotest

[GuillaumeGomez]

failures:
---- cyclic_dev_dep_doc_test stdout ----
running `C:\bot\slave\auto-win-msvc-64-cargotest\build\obj\build\ct\cargo\target\debug\cargo test`
thread 'cyclic_dev_dep_doc_test' panicked at '
Expected: execs
but: differences:
6 - |running 1 test|
+ |running 0 tests|
7 - |test _0 ... ok|
+ ||
8 - ||
+ |test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured|
9 - |test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured|
+ ||
10 - ||
+
other output:
` Compiling foo v0.0.1 (file:///C:/bot/slave/auto-win-msvc-64-cargotest/build/obj/build/ct/cargo/target/cit/t14/foo)
Compiling bar v0.0.1 (file:///C:/bot/slave/auto-win-msvc-64-cargotest/build/obj/build/ct/cargo/target/cit/t14/foo/bar)
Finished debug [unoptimized + debuginfo] target(s) in 1.3 secs
Running target\debug\deps\foo-6688213a3cfc5207.exe
Doc-tests foo
`', C:/msys64/slave/auto-win-msvc-64-cargotest/cargo-home\registry\src\github.com-1ecc6299db9ec823\hamcrest-0.1.1\src\core.rs:31
note: Run with `RUST_BACKTRACE=1` for a backtrace.
failures:
cyclic_dev_dep_doc_test
test result: FAILED. 54 passed; 1 failed; 0 ignored; 0 measured
command did not execute successfully: "C:\\bot\\slave\\auto-win-msvc-64-cargotest\\build\\obj\\build\\x86_64-pc-windows-msvc\\stage2-tools\\x86_64-pc-windows-msvc\\release\\cargotest.exe" "C:\\bot\\slave\\auto-win-msvc-64-cargotest\\build\\obj\\build\\x86_64-pc-windows-msvc\\stage0/bin\\cargo.exe" "C:\\bot\\slave\\auto-win-msvc-64-cargotest\\build\\obj\\build\\ct"
expected success, got: exit code: 101

[eddyb]

@alexcrichton Should the PR Travis builds include cargotest?

[alexcrichton]

@eddyb yeah once we start gating on travis I'd like to look into PR test coverage

[eddyb]

@bors r=nrc

[bors]

📌 Commit e7264d0 has been approved by nrc

[bors]

⌛ Testing commit e7264d0 with merge d6d8d70...

[bors]

💔 Test failed - auto-win-gnu-32-opt-rustbuild

[eddyb]

Travis passed but the OSX builds are broken. @bors r=nrc

[bors]

📌 Commit 4be7786 has been approved by nrc

[bors]

⌛ Testing commit 4be7786 with merge 29abe6f...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-cargotest, auto-linux-64-cross-freebsd, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-cross-ios-opt, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-rustbuild
Approved by: nrc
Pushing 29abe6f to master...