Test the linkchecker itself.

Author: ehuss

src/bootstrap/builder/tests.rs

@@ -613,9 +613,14 @@ mod dist {
         // Note that the stages here are +1 than what they actually are because
         // Rustdoc::run swaps out the compiler with stage minus 1 if --stage is
         // not 0.
+        //
+        // The stage 0 copy is the one downloaded for bootstrapping. It is
+        // (currently) needed to run "cargo test" on the linkchecker, and
+        // should be relatively "free".
         assert_eq!(
             first(builder.cache.all::<tool::Rustdoc>()),
             &[
+                tool::Rustdoc { compiler: Compiler { host: a, stage: 0 } },
                 tool::Rustdoc { compiler: Compiler { host: a, stage: 1 } },
                 tool::Rustdoc { compiler: Compiler { host: a, stage: 2 } },
             ]

src/bootstrap/test.rs

@@ -124,8 +124,25 @@ You can skip linkcheck with --exclude src/tools/linkchecker"
 
         builder.info(&format!("Linkcheck ({})", host));
 
+        // Test the linkchecker itself.
+        let bootstrap_host = builder.config.build;
+        let compiler = builder.compiler(0, bootstrap_host);
+        let cargo = tool::prepare_tool_cargo(
+            builder,
+            compiler,
+            Mode::ToolBootstrap,
+            bootstrap_host,
+            "test",
+            "src/tools/linkchecker",
+            SourceType::InTree,
+            &[],
+        );
+        try_run(builder, &mut cargo.into());
+
+        // Build all the default documentation.
         builder.default_doc(&[]);
 
+        // Run the linkchecker.
         let _time = util::timeit(&builder);
         try_run(
             builder,