Auto merge of #122156 - Zoxc:side-effect-dep-node, r=oli-obk

Represent diagnostic side effects as dep nodes

This changes diagnostic to be tracked as a special dep node (`SideEffect`) instead of having a list of side effects associated with each dep node. `SideEffect` is always red and when forced, it emits the diagnostic and marks itself green. Each emitted diagnostic generates a new `SideEffect` with an unique dep node index.

Some implications of this:

- Diagnostic may now be emitted more than once as they can be emitted once when the `SideEffect` gets marked green and again if the task it depends on needs to be re-executed due to another node being red. It relies on deduplicating of diagnostics to avoid that.

- Anon tasks which emits diagnostics will no longer *incorrectly* be merged with other anon tasks.

- Reusing a CGU will now emit diagnostics from the task generating it.

1 files changed, 2 insertions, 3 deletions

diff --git a/compiler/rustc_interface/src/callbacks.rs b/compiler/rustc_interface/src/callbacks.rs
index f66b9eb3a28..7c6b7157f71 100644
--- a/compiler/rustc_interface/src/callbacks.rs
+++ b/compiler/rustc_interface/src/callbacks.rs
@@ -14,6 +14,7 @@ use std::fmt;
 use rustc_errors::{DiagInner, TRACK_DIAGNOSTIC};
 use rustc_middle::dep_graph::{DepNodeExt, TaskDepsRef};
 use rustc_middle::ty::tls;
+use rustc_query_impl::QueryCtxt;
 use rustc_query_system::dep_graph::dep_node::default_dep_kind_debug;
 use rustc_query_system::dep_graph::{DepContext, DepKind, DepNode};
 
@@ -41,9 +42,7 @@ fn track_span_parent(def_id: rustc_span::def_id::LocalDefId) {
 fn track_diagnostic<R>(diagnostic: DiagInner, f: &mut dyn FnMut(DiagInner) -> R) -> R {
     tls::with_context_opt(|icx| {
         if let Some(icx) = icx {
-            if let Some(diagnostics) = icx.diagnostics {
-                diagnostics.lock().extend(Some(diagnostic.clone()));
-            }
+            icx.tcx.dep_graph.record_diagnostic(QueryCtxt::new(icx.tcx), &diagnostic);
 
             // Diagnostics are tracked, we can ignore the dependency.
             let icx = tls::ImplicitCtxt { task_deps: TaskDepsRef::Ignore, ..icx.clone() };