Fix `x test cargo`

3 files changed, 31 insertions, 36 deletions

diff --git a/src/bootstrap/src/core/build_steps/test.rs b/src/bootstrap/src/core/build_steps/test.rs
index c5e18f61047..5a3859792c7 100644
--- a/src/bootstrap/src/core/build_steps/test.rs
+++ b/src/bootstrap/src/core/build_steps/test.rs
@@ -18,7 +18,8 @@ use crate::core::build_steps::llvm::get_llvm_version;
 use crate::core::build_steps::run::get_completion_paths;
 use crate::core::build_steps::synthetic_targets::MirOptPanicAbortSyntheticTarget;
 use crate::core::build_steps::tool::{
-    self, COMPILETEST_ALLOW_FEATURES, RustcPrivateCompilers, SourceType, Tool,
+    self, COMPILETEST_ALLOW_FEATURES, RustcPrivateCompilers, SourceType, Tool, ToolTargetBuildMode,
+    get_tool_target_compiler,
 };
 use crate::core::build_steps::toolstate::ToolState;
 use crate::core::build_steps::{compile, dist, llvm};
@@ -293,7 +294,7 @@ impl Step for Cargotest {
 /// Runs `cargo test` for cargo itself.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Cargo {
-    stage: u32,
+    build_compiler: Compiler,
     host: TargetSelection,
 }
 
@@ -310,35 +311,29 @@ impl Step for Cargo {
     }
 
     fn make_run(run: RunConfig<'_>) {
-        // If stage is explicitly set or not lower than 2, keep it. Otherwise, make sure it's at least 2
-        // as tests for this step don't work with a lower stage.
-        let stage = if run.builder.config.is_explicit_stage() || run.builder.top_stage >= 2 {
-            run.builder.top_stage
-        } else {
-            2
-        };
-
-        run.builder.ensure(Cargo { stage, host: run.target });
+        run.builder.ensure(Cargo {
+            build_compiler: get_tool_target_compiler(
+                run.builder,
+                ToolTargetBuildMode::Build(run.target),
+            ),
+            host: run.target,
+        });
     }
 
     /// Runs `cargo test` for `cargo` packaged with Rust.
     fn run(self, builder: &Builder<'_>) {
-        let stage = self.stage;
-
-        if stage < 2 {
-            eprintln!("WARNING: cargo tests on stage {stage} may not behave well.");
-            eprintln!("HELP: consider using stage 2");
-        }
-
-        let compiler = builder.compiler(stage, self.host);
-
-        let cargo = builder.ensure(tool::Cargo::from_build_compiler(compiler, self.host));
-        let compiler = cargo.build_compiler;
+        // FIXME: we now use the same compiler to build cargo and then we also test that compiler
+        // using cargo.
+        // We could build cargo using a different compiler, but that complicates some things,
+        // because when we run cargo tests, the crates that are being compiled are accessing the
+        // sysroot of the build compiler, rather than the compiler being tested.
+        // Since these two compilers are currently the same, it works.
+        builder.ensure(tool::Cargo::from_build_compiler(self.build_compiler, self.host));
 
         let cargo = tool::prepare_tool_cargo(
             builder,
-            compiler,
-            Mode::ToolRustc,
+            self.build_compiler,
+            Mode::ToolTarget,
             self.host,
             Kind::Test,
             Self::CRATE_PATH,
@@ -355,7 +350,7 @@ impl Step for Cargo {
         // Forcibly disable tests using nightly features since any changes to
         // those features won't be able to land.
         cargo.env("CARGO_TEST_DISABLE_NIGHTLY", "1");
-        cargo.env("PATH", path_for_cargo(builder, compiler));
+        cargo.env("PATH", path_for_cargo(builder, self.build_compiler));
         // Cargo's test suite uses `CARGO_RUSTC_CURRENT_DIR` to determine the path that `file!` is
         // relative to. Cargo no longer sets this env var, so we have to do that. This has to be the
         // same value as `-Zroot-dir`.
@@ -367,7 +362,7 @@ impl Step for Cargo {
                 crates: vec!["cargo".into()],
                 target: self.host.triple.to_string(),
                 host: self.host.triple.to_string(),
-                stage,
+                stage: self.build_compiler.stage + 1,
             },
             builder,
         );
diff --git a/src/bootstrap/src/core/build_steps/tool.rs b/src/bootstrap/src/core/build_steps/tool.rs
index 0dc9002d4e4..e3f49fa126e 100644
--- a/src/bootstrap/src/core/build_steps/tool.rs
+++ b/src/bootstrap/src/core/build_steps/tool.rs
@@ -841,6 +841,7 @@ impl Step for Cargo {
     fn run(self, builder: &Builder<'_>) -> ToolBuildResult {
         builder.build.require_submodule("src/tools/cargo", None);
 
+        builder.std(self.build_compiler, self.target);
         builder.ensure(ToolBuild {
             build_compiler: self.build_compiler,
             target: self.target,
@@ -849,7 +850,11 @@ impl Step for Cargo {
             path: "src/tools/cargo",
             source_type: SourceType::Submodule,
             extra_features: Vec::new(),
-            allow_features: "",
+            // Cargo is compilable with a stable compiler, but since we run in bootstrap,
+            // with RUSTC_BOOTSTRAP being set, some "clever" build scripts enable specialization
+            // based on this, which breaks stuff. We thus have to explicitly allow these features
+            // here.
+            allow_features: "min_specialization,specialization",
             cargo_args: Vec::new(),
             artifact_kind: ToolArtifactKind::Binary,
         })
diff --git a/src/bootstrap/src/core/builder/tests.rs b/src/bootstrap/src/core/builder/tests.rs
index 057f3784797..67ad60e308d 100644
--- a/src/bootstrap/src/core/builder/tests.rs
+++ b/src/bootstrap/src/core/builder/tests.rs
@@ -1606,12 +1606,8 @@ mod snapshot {
             ctx.config("test")
                 .path("cargo")
                 .render_steps(), @r"
-        [build] llvm <host>
-        [build] rustc 0 <host> -> rustc 1 <host>
-        [build] rustc 1 <host> -> std 1 <host>
-        [build] rustc 1 <host> -> rustc 2 <host>
-        [build] rustc 2 <host> -> cargo 3 <host>
-        [build] rustdoc 2 <host>
+        [build] rustc 0 <host> -> cargo 1 <host>
+        [build] rustdoc 0 <host>
         ");
     }
 
@@ -1626,9 +1622,8 @@ mod snapshot {
         [build] llvm <host>
         [build] rustc 0 <host> -> rustc 1 <host>
         [build] rustc 1 <host> -> std 1 <host>
-        [build] rustc 1 <host> -> rustc 2 <host>
-        [build] rustc 2 <host> -> cargo 3 <host>
-        [build] rustdoc 2 <host>
+        [build] rustc 1 <host> -> cargo 2 <host>
+        [build] rustdoc 1 <host>
         ");
     }