1 files changed, 27 insertions, 6 deletions
diff --git a/compiler/rustc_query_system/src/query/job.rs b/compiler/rustc_query_system/src/query/job.rs
index 45b4079fb..ed65393f5 100644
--- a/compiler/rustc_query_system/src/query/job.rs
+++ b/compiler/rustc_query_system/src/query/job.rs
@@ -3,9 +3,11 @@ use crate::query::plumbing::CycleError;
 use crate::query::{QueryContext, QueryStackFrame};
 
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::{Diagnostic, DiagnosticBuilder, ErrorGuaranteed, Handler, Level};
+use rustc_errors::{
+    Diagnostic, DiagnosticBuilder, ErrorGuaranteed, Handler, IntoDiagnostic, Level,
+};
 use rustc_hir::def::DefKind;
-use rustc_session::{Session, SessionDiagnostic};
+use rustc_session::Session;
 use rustc_span::Span;
 
 use std::hash::Hash;
@@ -59,6 +61,7 @@ impl QueryJobId {
     }
 }
 
+#[derive(Clone)]
 pub struct QueryJobInfo {
     pub query: QueryStackFrame,
     pub job: QueryJob,
@@ -116,10 +119,10 @@ impl QueryJob {
     }
 }
 
-#[cfg(not(parallel_compiler))]
 impl QueryJobId {
     #[cold]
     #[inline(never)]
+    #[cfg(not(parallel_compiler))]
     pub(super) fn find_cycle_in_stack(
         &self,
         query_map: QueryMap,
@@ -156,6 +159,24 @@ impl QueryJobId {
 
         panic!("did not find a cycle")
     }
+
+    #[cold]
+    #[inline(never)]
+    pub fn try_find_layout_root(&self, query_map: QueryMap) -> Option<(QueryJobInfo, usize)> {
+        let mut last_layout = None;
+        let mut current_id = Some(*self);
+        let mut depth = 0;
+
+        while let Some(id) = current_id {
+            let info = query_map.get(&id).unwrap();
+            if info.query.name == "layout_of" {
+                depth += 1;
+                last_layout = Some((info.clone(), depth));
+            }
+            current_id = info.job.parent;
+        }
+        last_layout
+    }
 }
 
 #[cfg(parallel_compiler)]
@@ -530,7 +551,7 @@ pub fn deadlock(query_map: QueryMap, registry: &rayon_core::Registry) {
 #[cold]
 pub(crate) fn report_cycle<'a>(
     sess: &'a Session,
-    CycleError { usage, cycle: stack }: CycleError,
+    CycleError { usage, cycle: stack }: &CycleError,
 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
     assert!(!stack.is_empty());
 
@@ -548,10 +569,10 @@ pub(crate) fn report_cycle<'a>(
     }
 
     let mut cycle_usage = None;
-    if let Some((span, query)) = usage {
+    if let Some((span, ref query)) = *usage {
         cycle_usage = Some(crate::error::CycleUsage {
             span: query.default_span(span),
-            usage: query.description,
+            usage: query.description.to_string(),
         });
     }