Add strikethrough support to rustdoc

[mibac138]

Implements uncontroversial part of #71183.
r? @GuillaumeGomez

[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.

========================== Starting Command Output ===========================
[command]/bin/bash --noprofile --norc /home/vsts/work/_temp/d5ecdb59-f004-4c26-8f7d-f3e897ef29b2.sh

##[section]Finishing: Disable git automatic line ending conversion
##[section]Starting: Checkout rust-lang/rust@refs/pull/71928/merge to s
Task         : Get sources
Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
Version      : 1.0.0
Author       : Microsoft
---
##[command]git remote add origin https://github.com/rust-lang/rust
##[command]git config gc.auto 0
##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
##[command]git config --get-all http.proxy
##[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/71928/merge:refs/remotes/pull/71928/merge
---
 ---> f7353ccad5b1
Step 6/7 : ENV RUN_CHECK_WITH_PARALLEL_QUERIES 1
 ---> Using cache
 ---> ed38efbaa060
Step 7/7 : ENV SCRIPT python3 ../x.py test src/tools/expand-yaml-anchors &&            python3 ../x.py check --target=i686-pc-windows-gnu --host=i686-pc-windows-gnu &&            python3 ../x.py build --stage 0 src/tools/build-manifest &&            python3 ../x.py test --stage 0 src/tools/compiletest &&            python3 ../x.py test src/tools/tidy &&            /scripts/validate-toolstate.sh
 ---> c5008ef7ae8e
Successfully built c5008ef7ae8e
Successfully tagged rust-ci:latest
Built container sha256:c5008ef7ae8e94d7ef502e3cef26e61208e14ebdb36913f3a8bb86291bd6430b
---
    Checking rustc_feature v0.0.0 (/checkout/src/librustc_feature)
    Checking fmt_macros v0.0.0 (/checkout/src/libfmt_macros)
    Checking rustc_ast_pretty v0.0.0 (/checkout/src/librustc_ast_pretty)
    Checking rustc_hir v0.0.0 (/checkout/src/librustc_hir)
    Checking rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
    Checking rustc_parse v0.0.0 (/checkout/src/librustc_parse)
    Checking rustc_hir_pretty v0.0.0 (/checkout/src/librustc_hir_pretty)
    Checking rustc_ast_lowering v0.0.0 (/checkout/src/librustc_ast_lowering)
    Checking rustc_ast_passes v0.0.0 (/checkout/src/librustc_ast_passes)
---
configure: build.cargo-native-static := True
configure: build.locked-deps    := True
configure: llvm.ccache          := sccache
configure: rust.dist-src        := False
configure: build.configure-args := ['--enable-sccache', '--disable-manage-submodu ...
configure: writing `config.toml` in current directory
configure: 
configure: run `python /checkout/x.py --help`
configure: 
---
Hugepagesize:       2048 kB
DirectMap4k:      135104 kB
DirectMap2M:     3010560 kB
DirectMap1G:     6291456 kB
+ python3 ../x.py test src/tools/expand-yaml-anchors
Ensuring the YAML anchors in the GitHub Actions config were expanded
Ensuring the YAML anchors in the GitHub Actions config were expanded
Building stage0 tool expand-yaml-anchors (x86_64-unknown-linux-gnu)
   Compiling unicode-xid v0.2.0
   Compiling syn v1.0.11
   Compiling linked-hash-map v0.5.2
   Compiling lazy_static v1.4.0
   Compiling lazy_static v1.4.0
   Compiling yaml-rust v0.4.3
   Compiling quote v1.0.2
   Compiling thiserror-impl v1.0.5
   Compiling thiserror v1.0.5
   Compiling yaml-merge-keys v0.4.0
   Compiling expand-yaml-anchors v0.1.0 (/checkout/src/tools/expand-yaml-anchors)
Build completed successfully in 0:00:32
+ python3 ../x.py check --target=i686-pc-windows-gnu --host=i686-pc-windows-gnu
    Finished dev [unoptimized] target(s) in 0.23s
Checking rustdoc artifacts (x86_64-unknown-linux-gnu -> i686-pc-windows-gnu)
---
    Checking rustc_feature v0.0.0 (/checkout/src/librustc_feature)
    Checking fmt_macros v0.0.0 (/checkout/src/libfmt_macros)
    Checking rustc_ast_pretty v0.0.0 (/checkout/src/librustc_ast_pretty)
    Checking rustc_hir v0.0.0 (/checkout/src/librustc_hir)
    Checking rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
    Checking rustc_parse v0.0.0 (/checkout/src/librustc_parse)
    Checking rustc_hir_pretty v0.0.0 (/checkout/src/librustc_hir_pretty)
    Checking rustc_ast_lowering v0.0.0 (/checkout/src/librustc_ast_lowering)
    Checking rustc_ast_passes v0.0.0 (/checkout/src/librustc_ast_passes)
---
Diff in /checkout/src/librustdoc/html/markdown.rs at line 933:
             }
         };
 
-        let p = Parser::new_with_broken_link_callback(md, Options::ENABLE_STRIKETHROUGH, Some(&replacer));
+        let p = Parser::new_with_broken_link_callback(
+            md,
+            Options::ENABLE_STRIKETHROUGH,
+            Some(&replacer),
 
         let mut s = String::new();
 
Diff in /checkout/src/librustdoc/html/markdown.rs at line 975:
Diff in /checkout/src/librustdoc/html/markdown.rs at line 975:
         }
     }
     let mut s = String::with_capacity(md.len() * 3 / 2);
-    let p = ParserWrapper { inner: Parser::new_ext(md, Options::ENABLE_STRIKETHROUGH), is_in: 0, is_first: true };
+    let p = ParserWrapper {
+        inner: Parser::new_ext(md, Options::ENABLE_STRIKETHROUGH),
+        is_in: 0,
+    };
+    };
     p.filter(|t| !t.is_empty()).for_each(|i| s.push_str(&i));
 }
 }
Running `"/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/rustfmt" "--config-path" "/checkout" "--edition" "2018" "--unstable-features" "--skip-children" "--check" "/checkout/src/librustdoc/html/markdown.rs"` failed.
If you're running `tidy`, try again with `--bless` flag. Or, you just want to format code, run `./x.py fmt` instead.
Build completed unsuccessfully in 0:00:47
== clock drift check ==
  local time: Tue May  5 19:09:33 UTC 2020
  network time: Tue, 05 May 2020 19:09:33 GMT
  network time: Tue, 05 May 2020 19:09:33 GMT
== end clock drift check ==

##[error]Bash exited with code '1'.
##[section]Finishing: Run build
##[section]Starting: Checkout rust-lang/rust@refs/pull/71928/merge to s
Task         : Get sources
Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
Version      : 1.0.0
Author       : Microsoft
Author       : Microsoft
Help         : [More Information](https://go.microsoft.com/fwlink/?LinkId=798199)
==============================================================================
Cleaning any cached credential from repository: rust-lang/rust (GitHub)
##[section]Finishing: Checkout rust-lang/rust@refs/pull/71928/merge to s
Cleaning up task key
Start cleaning up orphan processes.
Terminate orphan process: pid (3620) (python)
##[section]Finishing: Finalize Job

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 @rust-lang/infra. (Feature Requests)

[GuillaumeGomez]

Looks good to me. Can you please add a test for the generated HTML? (It's in src/test/rustdoc)

[mibac138]

@GuillaumeGomez sure thing, added

[GuillaumeGomez]

Thanks!

@bors: r+ rollup

[bors]

📌 Commit bbda107 has been approved by GuillaumeGomez