1 files changed, 98 insertions, 72 deletions

diff --git a/crates/project_model/src/workspace.rs b/crates/project_model/src/workspace.rs
index b969420cf..b2ca7a4d2 100644
--- a/crates/project_model/src/workspace.rs
+++ b/crates/project_model/src/workspace.rs
@@ -376,6 +376,7 @@ fn cargo_to_crate_graph(
     cfg_options.insert_atom("debug_assertions".into());
 
     let mut pkg_crates = FxHashMap::default();
+    // Does any crate signal to rust-analyzer that they need the rustc_private crates?
     let mut has_private = false;
     // Next, create crates for each package, target pair
     for pkg in cargo.packages() {
@@ -440,92 +441,117 @@ fn cargo_to_crate_graph(
         }
     }
 
-    let mut rustc_pkg_crates = FxHashMap::default();
-
     if has_private {
         // If the user provided a path to rustc sources, we add all the rustc_private crates
         // and create dependencies on them for the crates which opt-in to that
         if let Some(rustc_workspace) = rustc {
-            // rustc-dev crates start from 'rustc_driver'
-            // We want to collect all crates which are transitive dependencies of rustc_driver
-            if let Some(root_pkg) = rustc_workspace
-                .packages()
-                .find(|package| rustc_workspace[*package].name == "rustc_driver")
-            {
-                let mut queue = VecDeque::new();
-                queue.push_back(root_pkg);
-                while let Some(pkg) = queue.pop_front() {
-                    // Don't duplicate packages
-                    if rustc_pkg_crates.contains_key(&pkg) {
-                        continue;
-                    }
-                    for dep in &rustc_workspace[pkg].dependencies {
-                        queue.push_back(dep.pkg);
-                    }
-                    for &tgt in rustc_workspace[pkg].targets.iter() {
-                        if rustc_workspace[tgt].kind != TargetKind::Lib {
-                            continue;
-                        }
-                        if let Some(file_id) = load(&rustc_workspace[tgt].root) {
-                            let crate_id = add_target_crate_root(
-                                &mut crate_graph,
-                                &rustc_workspace[pkg],
-                                rustc_build_data_map
-                                    .and_then(|it| it.get(&rustc_workspace[pkg].id)),
-                                &cfg_options,
-                                proc_macro_loader,
-                                file_id,
-                            );
-                            pkg_to_lib_crate.insert(pkg, crate_id);
-                            // Add dependencies on the core / std / alloc for rustc
-                            for (name, krate) in public_deps.iter() {
-                                add_dep(&mut crate_graph, crate_id, name.clone(), *krate);
-                            }
-                            rustc_pkg_crates.entry(pkg).or_insert_with(Vec::new).push(crate_id);
-                        }
+            handle_rustc_crates(
+                rustc_workspace,
+                load,
+                &mut crate_graph,
+                rustc_build_data_map,
+                &cfg_options,
+                proc_macro_loader,
+                &mut pkg_to_lib_crate,
+                &public_deps,
+                cargo,
+                &pkg_crates,
+            );
+        }
+    }
+    crate_graph
+}
+
+fn handle_rustc_crates(
+    rustc_workspace: &CargoWorkspace,
+    load: &mut dyn FnMut(&AbsPath) -> Option<FileId>,
+    crate_graph: &mut CrateGraph,
+    rustc_build_data_map: Option<&FxHashMap<String, BuildData>>,
+    cfg_options: &CfgOptions,
+    proc_macro_loader: &dyn Fn(&Path) -> Vec<ProcMacro>,
+    pkg_to_lib_crate: &mut FxHashMap<la_arena::Idx<crate::PackageData>, CrateId>,
+    public_deps: &[(CrateName, CrateId)],
+    cargo: &CargoWorkspace,
+    pkg_crates: &FxHashMap<la_arena::Idx<crate::PackageData>, Vec<CrateId>>,
+) {
+    let mut rustc_pkg_crates = FxHashMap::default();
+    // The root package of the rustc-dev component is rustc_driver, so we match that
+    let root_pkg =
+        rustc_workspace.packages().find(|package| rustc_workspace[*package].name == "rustc_driver");
+    // The rustc workspace might be incomplete (such as if rustc-dev is not installed for the current toolchain)
+    // and `rustcSource` is set to discover.
+    if let Some(root_pkg) = root_pkg {
+        // Iterate through every crate in the dependency subtree of rustc_driver using BFS
+        let mut queue = VecDeque::new();
+        queue.push_back(root_pkg);
+        while let Some(pkg) = queue.pop_front() {
+            // Don't duplicate packages if they are dependended on a diamond pattern
+            // N.B. if this line is ommitted, we try and analyse either 48_000 or 480_000 crates
+            // neither of which makes
+            if rustc_pkg_crates.contains_key(&pkg) {
+                continue;
+            }
+            for dep in &rustc_workspace[pkg].dependencies {
+                queue.push_back(dep.pkg);
+            }
+            for &tgt in rustc_workspace[pkg].targets.iter() {
+                if rustc_workspace[tgt].kind != TargetKind::Lib {
+                    continue;
+                }
+                if let Some(file_id) = load(&rustc_workspace[tgt].root) {
+                    let crate_id = add_target_crate_root(
+                        crate_graph,
+                        &rustc_workspace[pkg],
+                        rustc_build_data_map.and_then(|it| it.get(&rustc_workspace[pkg].id)),
+                        &cfg_options,
+                        proc_macro_loader,
+                        file_id,
+                    );
+                    pkg_to_lib_crate.insert(pkg, crate_id);
+                    // Add dependencies on core / std / alloc for this crate
+                    for (name, krate) in public_deps.iter() {
+                        add_dep(crate_graph, crate_id, name.clone(), *krate);
                     }
+                    rustc_pkg_crates.entry(pkg).or_insert_with(Vec::new).push(crate_id);
                 }
             }
-            // Now add a dep edge from all targets of upstream to the lib
-            // target of downstream.
-            for pkg in rustc_pkg_crates.keys().copied() {
-                for dep in rustc_workspace[pkg].dependencies.iter() {
-                    let name = CrateName::new(&dep.name).unwrap();
-                    if let Some(&to) = pkg_to_lib_crate.get(&dep.pkg) {
-                        for &from in rustc_pkg_crates.get(&pkg).into_iter().flatten() {
-                            add_dep(&mut crate_graph, from, name.clone(), to);
-                        }
-                    }
+        }
+    }
+    // Now add a dep edge from all targets of upstream to the lib
+    // target of downstream.
+    for pkg in rustc_pkg_crates.keys().copied() {
+        for dep in rustc_workspace[pkg].dependencies.iter() {
+            let name = CrateName::new(&dep.name).unwrap();
+            if let Some(&to) = pkg_to_lib_crate.get(&dep.pkg) {
+                for &from in rustc_pkg_crates.get(&pkg).into_iter().flatten() {
+                    add_dep(crate_graph, from, name.clone(), to);
                 }
             }
-
-            // Add dependencies for all crates which opt in to rustc_private libraries
-            for dep in rustc_workspace.packages() {
-                let name = CrateName::normalize_dashes(&rustc_workspace[dep].name);
-
-                if let Some(&to) = pkg_to_lib_crate.get(&dep) {
-                    for pkg in cargo.packages() {
-                        let package = &cargo[pkg];
-                        if !package.metadata.rustc_private {
-                            continue;
-                        }
-                        for &from in pkg_crates.get(&pkg).into_iter().flatten() {
-                            // Avoid creating duplicate dependencies
-                            if !crate_graph[from].dependencies.iter().any(|d| d.name == name) {
-                                add_dep(&mut crate_graph, from, name.clone(), to);
-                            } else {
-                                eprintln!(
-                                    "Skipped {} for {:?}",
-                                    &name, &crate_graph[from].display_name
-                                );
-                            }
-                        }
+        }
+    }
+    // Add a dependency on the rustc_private crates for all targets of each package
+    // which opts in
+    for dep in rustc_workspace.packages() {
+        let name = CrateName::normalize_dashes(&rustc_workspace[dep].name);
+
+        if let Some(&to) = pkg_to_lib_crate.get(&dep) {
+            for pkg in cargo.packages() {
+                let package = &cargo[pkg];
+                if !package.metadata.rustc_private {
+                    continue;
+                }
+                for &from in pkg_crates.get(&pkg).into_iter().flatten() {
+                    // Avoid creating duplicate dependencies
+                    // This avoids the situation where `from` depends on e.g. `arrayvec`, but
+                    // `rust_analyzer` thinks that it should use the one from the `rustcSource`
+                    // instead of the one from `crates.io`
+                    if !crate_graph[from].dependencies.iter().any(|d| d.name == name) {
+                        add_dep(crate_graph, from, name.clone(), to);
                     }
                 }
             }
         }
     }
-    crate_graph
 }
 
 fn add_target_crate_root(