handle no_std targets on std builds

src/bootstrap/src/core/build_steps/check.rs

@@ -3,7 +3,7 @@
 use std::path::PathBuf;
 
 use crate::core::build_steps::compile::{
-    add_to_sysroot, run_cargo, rustc_cargo, rustc_cargo_env, std_cargo,
+    add_to_sysroot, run_cargo, rustc_cargo, rustc_cargo_env, std_cargo, std_crates_for_run_make,
 };
 use crate::core::build_steps::tool::{prepare_tool_cargo, SourceType};
 use crate::core::builder::{
@@ -49,7 +49,7 @@ impl Step for Std {
     }
 
     fn make_run(run: RunConfig<'_>) {
-        let crates = run.make_run_crates(Alias::Library);
+        let crates = std_crates_for_run_make(&run);
         run.builder.ensure(Std { target: run.target, crates, override_build_kind: None });
     }
 

src/bootstrap/src/core/build_steps/clippy.rs

@@ -4,6 +4,7 @@ use super::compile::{librustc_stamp, libstd_stamp, run_cargo, rustc_cargo, std_c
 use super::tool::{prepare_tool_cargo, SourceType};
 use super::{check, compile};
 use crate::builder::{Builder, ShouldRun};
+use crate::core::build_steps::compile::std_crates_for_run_make;
 use crate::core::builder;
 use crate::core::builder::{crate_description, Alias, Kind, RunConfig, Step};
 use crate::{Mode, Subcommand, TargetSelection};
@@ -106,7 +107,7 @@ impl Step for Std {
     }
 
     fn make_run(run: RunConfig<'_>) {
-        let crates = run.make_run_crates(Alias::Library);
+        let crates = std_crates_for_run_make(&run);
         run.builder.ensure(Std { target: run.target, crates });
     }
 

src/bootstrap/src/core/build_steps/compile.rs

@@ -123,11 +123,7 @@ impl Step for Std {
     }
 
     fn make_run(run: RunConfig<'_>) {
-        // If the paths include "library", build the entire standard library.
-        let has_alias =
-            run.paths.iter().any(|set| set.assert_single_path().path.ends_with("library"));
-        let crates = if has_alias { Default::default() } else { run.cargo_crates_in_set() };
-
+        let crates = std_crates_for_run_make(&run);
         run.builder.ensure(Std {
             compiler: run.builder.compiler(run.builder.top_stage, run.build_triple()),
             target: run.target,
@@ -425,6 +421,28 @@ fn copy_self_contained_objects(
     target_deps
 }
 
+/// Resolves standard library crates for `Std::run_make` for any build kind (like check, build, clippy, etc.).
+pub fn std_crates_for_run_make(run: &RunConfig<'_>) -> Vec<String> {
+    // FIXME: Extend builder tests to cover the `crates` field of `Std` instances.
+    if cfg!(feature = "bootstrap-self-test") {
+        return vec![];
+    }
+
+    let has_alias = run.paths.iter().any(|set| set.assert_single_path().path.ends_with("library"));
+    let target_is_no_std = run.builder.no_std(run.target).unwrap_or(false);
+
+    // For no_std targets, do not add any additional crates to the compilation other than what `compile::std_cargo` already adds for no_std targets.
+    if target_is_no_std {
+        vec![]
+    }
+    // If the paths include "library", build the entire standard library.
+    else if has_alias {
+        run.make_run_crates(builder::Alias::Library)
+    } else {
+        run.cargo_crates_in_set()
+    }
+}
+
 /// Configure cargo to compile the standard library, adding appropriate env vars
 /// and such.
 pub fn std_cargo(builder: &Builder<'_>, target: TargetSelection, stage: u32, cargo: &mut Cargo) {

src/bootstrap/src/core/build_steps/dist.rs

@@ -106,7 +106,6 @@ impl Step for JsonDocs {
         builder.ensure(crate::core::build_steps::doc::Std::new(
             builder.top_stage,
             host,
-            builder,
             DocumentationFormat::Json,
         ));
 

src/bootstrap/src/core/build_steps/doc.rs

@@ -564,18 +564,8 @@ pub struct Std {
 }
 
 impl Std {
-    pub(crate) fn new(
-        stage: u32,
-        target: TargetSelection,
-        builder: &Builder<'_>,
-        format: DocumentationFormat,
-    ) -> Self {
-        let crates = builder
-            .in_tree_crates("sysroot", Some(target))
-            .into_iter()
-            .map(|krate| krate.name.to_string())
-            .collect();
-        Std { stage, target, format, crates }
+    pub(crate) fn new(stage: u32, target: TargetSelection, format: DocumentationFormat) -> Self {
+        Std { stage, target, format, crates: vec![] }
     }
 }
 
@@ -589,6 +579,7 @@ impl Step for Std {
     }
 
     fn make_run(run: RunConfig<'_>) {
+        let crates = compile::std_crates_for_run_make(&run);
         run.builder.ensure(Std {
             stage: run.builder.top_stage,
             target: run.target,
@@ -597,7 +588,7 @@ impl Step for Std {
             } else {
                 DocumentationFormat::Html
             },
-            crates: run.make_run_crates(Alias::Library),
+            crates,
         });
     }
 
@@ -695,13 +686,6 @@ fn doc_std(
     extra_args: &[&str],
     requested_crates: &[String],
 ) {
-    if builder.no_std(target) == Some(true) {
-        panic!(
-            "building std documentation for no_std target {target} is not supported\n\
-             Set `docs = false` in the config to disable documentation, or pass `--skip library`."
-        );
-    }
-
     let compiler = builder.compiler(stage, builder.config.build);
 
     let target_doc_dir_name = if format == DocumentationFormat::Json { "json-doc" } else { "doc" };

src/bootstrap/src/core/build_steps/test.rs

@@ -847,7 +847,6 @@ impl Step for RustdocJSStd {
         builder.ensure(crate::core::build_steps::doc::Std::new(
             builder.top_stage,
             self.target,
-            builder,
             DocumentationFormat::Html,
         ));
         let _guard = builder.msg(

src/bootstrap/src/core/builder/tests.rs

@@ -79,13 +79,9 @@ macro_rules! std {
 
 macro_rules! doc_std {
     ($host:ident => $target:ident, stage = $stage:literal) => {{
-        let config = configure("doc", &["A-A"], &["A-A"]);
-        let build = Build::new(config);
-        let builder = Builder::new(&build);
         doc::Std::new(
             $stage,
             TargetSelection::from_user(concat!(stringify!($target), "-", stringify!($target))),
-            &builder,
             DocumentationFormat::Html,
         )
     }};