Add core lib to proc_macro dependencies

crates/project-model/src/sysroot.rs

@@ -276,4 +276,7 @@ fn get_rust_src(sysroot_path: &AbsPath) -> Option<AbsPathBuf> {
 std_detect
 test";
 
-const PROC_MACRO_DEPS: &str = "std";
+// core is required for our builtin derives to work in the proc_macro lib currently
+const PROC_MACRO_DEPS: &str = "
+std
+core";

crates/project-model/src/tests.rs

@@ -1547,6 +1547,15 @@ fn rust_project_hello_world_project_model() {
                                 ),
                                 prelude: true,
                             },
+                            Dependency {
+                                crate_id: CrateId(
+                                    1,
+                                ),
+                                name: CrateName(
+                                    "core",
+                                ),
+                                prelude: true,
+                            },
                         ],
                         proc_macro: Err(
                             "no proc macro loaded for sysroot crate",