Pass --target to lint docs

Otherwise, we may not have a standard library built for the native "host" target
of the rustc being run.

src/bootstrap/doc.rs

@@ -752,6 +752,7 @@ impl Step for RustcBook {
         let out_listing = out_base.join("src/lints");
         builder.cp_r(&builder.src.join("src/doc/rustc"), &out_base);
         builder.info(&format!("Generating lint docs ({})", self.target));
+
         let rustc = builder.rustc(self.compiler);
         // The tool runs `rustc` for extracting output examples, so it needs a
         // functional sysroot.
@@ -762,7 +763,8 @@ impl Step for RustcBook {
         cmd.arg("--out");
         cmd.arg(&out_listing);
         cmd.arg("--rustc");
-        cmd.arg(rustc);
+        cmd.arg(&rustc);
+        cmd.arg("--rustc-target").arg(&self.target.rustc_target_arg());
         if builder.config.verbose() {
             cmd.arg("--verbose");
         }

src/tools/lint-docs/src/groups.rs

@@ -18,10 +18,10 @@ static GROUP_DESCRIPTIONS: &[(&str, &str)] = &[
 /// Updates the documentation of lint groups.
 pub(crate) fn generate_group_docs(
     lints: &[Lint],
-    rustc_path: &Path,
+    rustc: crate::Rustc<'_>,
     out_path: &Path,
 ) -> Result<(), Box<dyn Error>> {
-    let groups = collect_groups(rustc_path)?;
+    let groups = collect_groups(rustc)?;
     let groups_path = out_path.join("groups.md");
     let contents = fs::read_to_string(&groups_path)
         .map_err(|e| format!("could not read {}: {}", groups_path.display(), e))?;
@@ -36,9 +36,9 @@ pub(crate) fn generate_group_docs(
 type LintGroups = BTreeMap<String, BTreeSet<String>>;
 
 /// Collects the group names from rustc.
-fn collect_groups(rustc: &Path) -> Result<LintGroups, Box<dyn Error>> {
+fn collect_groups(rustc: crate::Rustc<'_>) -> Result<LintGroups, Box<dyn Error>> {
     let mut result = BTreeMap::new();
-    let mut cmd = Command::new(rustc);
+    let mut cmd = Command::new(rustc.path);
     cmd.arg("-Whelp");
     let output = cmd.output().map_err(|e| format!("failed to run command {:?}\n{}", cmd, e))?;
     if !output.status.success() {

src/tools/lint-docs/src/lib.rs

@@ -45,16 +45,22 @@ impl Level {
     }
 }
 
+#[derive(Copy, Clone)]
+pub struct Rustc<'a> {
+    pub path: &'a Path,
+    pub target: &'a str,
+}
+
 /// Collects all lints, and writes the markdown documentation at the given directory.
 pub fn extract_lint_docs(
     src_path: &Path,
     out_path: &Path,
-    rustc_path: &Path,
+    rustc: Rustc<'_>,
     verbose: bool,
 ) -> Result<(), Box<dyn Error>> {
     let mut lints = gather_lints(src_path)?;
     for lint in &mut lints {
-        generate_output_example(lint, rustc_path, verbose).map_err(|e| {
+        generate_output_example(lint, rustc, verbose).map_err(|e| {
             format!(
                 "failed to test example in lint docs for `{}` in {}:{}: {}",
                 lint.name,
@@ -65,7 +71,7 @@ pub fn extract_lint_docs(
         })?;
     }
     save_lints_markdown(&lints, &out_path.join("listing"))?;
-    groups::generate_group_docs(&lints, rustc_path, out_path)?;
+    groups::generate_group_docs(&lints, rustc, out_path)?;
     Ok(())
 }
 
@@ -208,7 +214,7 @@ fn lint_name(line: &str) -> Result<String, &'static str> {
 /// actual output from the compiler.
 fn generate_output_example(
     lint: &mut Lint,
-    rustc_path: &Path,
+    rustc: Rustc<'_>,
     verbose: bool,
 ) -> Result<(), Box<dyn Error>> {
     // Explicit list of lints that are allowed to not have an example. Please
@@ -230,7 +236,7 @@ fn generate_output_example(
     // separate test suite, and use an include mechanism such as mdbook's
     // `{{#rustdoc_include}}`.
     if !lint.is_ignored() {
-        replace_produces(lint, rustc_path, verbose)?;
+        replace_produces(lint, rustc, verbose)?;
     }
     Ok(())
 }
@@ -261,7 +267,7 @@ fn check_style(lint: &Lint) -> Result<(), Box<dyn Error>> {
 /// output from the compiler.
 fn replace_produces(
     lint: &mut Lint,
-    rustc_path: &Path,
+    rustc: Rustc<'_>,
     verbose: bool,
 ) -> Result<(), Box<dyn Error>> {
     let mut lines = lint.doc.iter_mut();
@@ -302,7 +308,7 @@ fn replace_produces(
                 Some(line) if line.is_empty() => {}
                 Some(line) if line == "{{produces}}" => {
                     let output =
-                        generate_lint_output(&lint.name, &example, &options, rustc_path, verbose)?;
+                        generate_lint_output(&lint.name, &example, &options, rustc, verbose)?;
                     line.replace_range(
                         ..,
                         &format!(
@@ -329,7 +335,7 @@ fn generate_lint_output(
     name: &str,
     example: &[&mut String],
     options: &[&str],
-    rustc_path: &Path,
+    rustc: Rustc<'_>,
     verbose: bool,
 ) -> Result<String, Box<dyn Error>> {
     if verbose {
@@ -364,13 +370,14 @@ fn generate_lint_output(
     }
     fs::write(&tempfile, source)
         .map_err(|e| format!("failed to write {}: {}", tempfile.display(), e))?;
-    let mut cmd = Command::new(rustc_path);
+    let mut cmd = Command::new(rustc.path);
     if options.contains(&"edition2015") {
         cmd.arg("--edition=2015");
     } else {
         cmd.arg("--edition=2018");
     }
     cmd.arg("--error-format=json");
+    cmd.arg("--target").arg(rustc.target);
     if options.contains(&"test") {
         cmd.arg("--test");
     }

src/tools/lint-docs/src/main.rs

@@ -13,6 +13,7 @@ fn doit() -> Result<(), Box<dyn Error>> {
     let mut src_path = None;
     let mut out_path = None;
     let mut rustc_path = None;
+    let mut rustc_target = None;
     let mut verbose = false;
     while let Some(arg) = args.next() {
         match arg.as_str() {
@@ -34,6 +35,12 @@ fn doit() -> Result<(), Box<dyn Error>> {
                     None => return Err("--rustc requires a value".into()),
                 };
             }
+            "--rustc-target" => {
+                rustc_target = match args.next() {
+                    Some(s) => Some(s),
+                    None => return Err("--rustc-target requires a value".into()),
+                };
+            }
             "-v" | "--verbose" => verbose = true,
             s => return Err(format!("unexpected argument `{}`", s).into()),
         }
@@ -47,10 +54,16 @@ fn doit() -> Result<(), Box<dyn Error>> {
     if rustc_path.is_none() {
         return Err("--rustc must be specified to the path of rustc".into());
     }
+    if rustc_target.is_none() {
+        return Err("--rustc-target must be specified to the rustc target".into());
+    }
     lint_docs::extract_lint_docs(
         &src_path.unwrap(),
         &out_path.unwrap(),
-        &rustc_path.unwrap(),
+        lint_docs::Rustc {
+            path: rustc_path.as_deref().unwrap(),
+            target: rustc_target.as_deref().unwrap(),
+        },
         verbose,
     )
 }