Auto merge of rust-lang#14348 - Veykril:rustc-proc, r=Veykril

fix: Fix rustc proc-macro handling being broken on the rustc workspace itself

Also addresses rust-lang/rust-analyzer#13591 (comment)

Author: bors

crates/project-model/src/build_scripts.rs

@@ -429,8 +429,9 @@ impl WorkspaceBuildScripts {
             for p in rustc.packages() {
                 let package = &rustc[p];
                 if package.targets.iter().any(|&it| rustc[it].is_proc_macro) {
-                    if let Some((_, path)) =
-                        proc_macro_dylibs.iter().find(|(name, _)| *name == package.name)
+                    if let Some((_, path)) = proc_macro_dylibs
+                        .iter()
+                        .find(|(name, _)| *name.trim_start_matches("lib") == package.name)
                     {
                         bs.outputs[p].proc_macro_dylib_path = Some(path.clone());
                     }

crates/project-model/src/workspace.rs

@@ -940,7 +940,7 @@ fn cargo_to_crate_graph(
     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, build_scripts)) = rustc {
+        if let Some((rustc_workspace, rustc_build_scripts)) = rustc {
             handle_rustc_crates(
                 &mut crate_graph,
                 &mut pkg_to_lib_crate,
@@ -953,7 +953,13 @@ fn cargo_to_crate_graph(
                 &pkg_crates,
                 &cfg_options,
                 override_cfg,
-                build_scripts,
+                if rustc_workspace.workspace_root() == cargo.workspace_root() {
+                    // the rustc workspace does not use the installed toolchain's proc-macro server
+                    // so we need to make sure we don't use the pre compiled proc-macros there either
+                    build_scripts
+                } else {
+                    rustc_build_scripts
+                },
                 target_layout,
             );
         }