From b9f76287c299719ae91c0cdf6a24da3ebf065ffc Mon Sep 17 00:00:00 2001
From: Lukas Wirth <lukastw97@gmail.com>
Date: Sun, 16 Feb 2025 10:51:58 +0100
Subject: [PATCH] Set `RUSTUP_TOOLCHAIN` when loading sysroot workspace

---
 crates/project-model/src/cargo_workspace.rs | 3 +++
 crates/project-model/src/sysroot.rs         | 5 +++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/crates/project-model/src/cargo_workspace.rs b/crates/project-model/src/cargo_workspace.rs
index e4a611346205..b5f4e43a115d 100644
--- a/crates/project-model/src/cargo_workspace.rs
+++ b/crates/project-model/src/cargo_workspace.rs
@@ -277,6 +277,9 @@ impl CargoWorkspace {
     /// Fetches the metadata for the given `cargo_toml` manifest.
     /// A successful result may contain another metadata error if the initial fetching failed but
     /// the `--no-deps` retry succeeded.
+    ///
+    /// The sysroot is used to set the `RUSTUP_TOOLCHAIN` env var when invoking cargo
+    /// to ensure that the rustup proxy uses the correct toolchain.
     pub fn fetch_metadata(
         cargo_toml: &ManifestPath,
         current_dir: &AbsPath,
diff --git a/crates/project-model/src/sysroot.rs b/crates/project-model/src/sysroot.rs
index 510c18dd147e..544ba43ba66f 100644
--- a/crates/project-model/src/sysroot.rs
+++ b/crates/project-model/src/sysroot.rs
@@ -247,7 +247,7 @@ impl Sysroot {
             let library_manifest = ManifestPath::try_from(src_root.join("Cargo.toml")).unwrap();
             if fs::metadata(&library_manifest).is_ok() {
                 if let Some(loaded) =
-                    Self::load_library_via_cargo(library_manifest, src_root, cargo_config)
+                    self.load_library_via_cargo(library_manifest, src_root, cargo_config)
                 {
                     return Some(loaded);
                 }
@@ -326,6 +326,7 @@ impl Sysroot {
     }
 
     fn load_library_via_cargo(
+        &self,
         library_manifest: ManifestPath,
         rust_lib_src_dir: &AbsPathBuf,
         cargo_config: &CargoMetadataConfig,
@@ -342,7 +343,7 @@ impl Sysroot {
             &library_manifest,
             rust_lib_src_dir,
             &cargo_config,
-            &Sysroot::empty(),
+            self,
             // Make sure we never attempt to write to the sysroot
             true,
             &|_| (),