From 20c648c5827a2a774f4b6aeb36804c845130659b Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Thu, 17 Aug 2023 14:33:24 -0700
Subject: [PATCH] Normalize before checking if local is freeze in
 deduced_param_attrs

---
 .../src/deduce_param_attrs.rs                 |   7 +-
 .../ui/async-await/deep-futures-are-freeze.rs | 179 ++++++++++++++++++
 2 files changed, 185 insertions(+), 1 deletion(-)
 create mode 100644 tests/ui/async-await/deep-futures-are-freeze.rs

diff --git a/compiler/rustc_mir_transform/src/deduce_param_attrs.rs b/compiler/rustc_mir_transform/src/deduce_param_attrs.rs
index 60ca3dfb2dab5..79645310a3987 100644
--- a/compiler/rustc_mir_transform/src/deduce_param_attrs.rs
+++ b/compiler/rustc_mir_transform/src/deduce_param_attrs.rs
@@ -203,7 +203,12 @@ pub fn deduced_param_attrs<'tcx>(
         body.local_decls.iter().skip(1).take(body.arg_count).enumerate().map(
             |(arg_index, local_decl)| DeducedParamAttrs {
                 read_only: !deduce_read_only.mutable_args.contains(arg_index)
-                    && local_decl.ty.is_freeze(tcx, param_env),
+                    // We must normalize here to reveal opaques and normalize
+                    // their substs, otherwise we'll see exponential blow-up in
+                    // compile times: #113372
+                    && tcx
+                        .normalize_erasing_regions(param_env, local_decl.ty)
+                        .is_freeze(tcx, param_env),
             },
         ),
     );
diff --git a/tests/ui/async-await/deep-futures-are-freeze.rs b/tests/ui/async-await/deep-futures-are-freeze.rs
new file mode 100644
index 0000000000000..dd676d5e18c02
--- /dev/null
+++ b/tests/ui/async-await/deep-futures-are-freeze.rs
@@ -0,0 +1,179 @@
+// build-pass
+// compile-flags: -Copt-level=s -Clto=fat
+// no-prefer-dynamic
+// edition: 2021
+
+#![recursion_limit = "256"]
+
+fn main() {
+    spawn(move || main0())
+}
+
+fn spawn<F>(future: impl FnOnce() -> F) {
+    future();
+}
+
+async fn main0() {
+    main1().await;
+    main2().await;
+}
+async fn main1() {
+    main2().await;
+    main3().await;
+}
+async fn main2() {
+    main3().await;
+    main4().await;
+}
+async fn main3() {
+    main4().await;
+    main5().await;
+}
+async fn main4() {
+    main5().await;
+    main6().await;
+}
+async fn main5() {
+    main6().await;
+    main7().await;
+}
+async fn main6() {
+    main7().await;
+    main8().await;
+}
+async fn main7() {
+    main8().await;
+    main9().await;
+}
+async fn main8() {
+    main9().await;
+    main10().await;
+}
+async fn main9() {
+    main10().await;
+    main11().await;
+}
+async fn main10() {
+    main11().await;
+    main12().await;
+}
+async fn main11() {
+    main12().await;
+    main13().await;
+}
+async fn main12() {
+    main13().await;
+    main14().await;
+}
+async fn main13() {
+    main14().await;
+    main15().await;
+}
+async fn main14() {
+    main15().await;
+    main16().await;
+}
+async fn main15() {
+    main16().await;
+    main17().await;
+}
+async fn main16() {
+    main17().await;
+    main18().await;
+}
+async fn main17() {
+    main18().await;
+    main19().await;
+}
+async fn main18() {
+    main19().await;
+    main20().await;
+}
+async fn main19() {
+    main20().await;
+    main21().await;
+}
+async fn main20() {
+    main21().await;
+    main22().await;
+}
+async fn main21() {
+    main22().await;
+    main23().await;
+}
+async fn main22() {
+    main23().await;
+    main24().await;
+}
+async fn main23() {
+    main24().await;
+    main25().await;
+}
+async fn main24() {
+    main25().await;
+    main26().await;
+}
+async fn main25() {
+    main26().await;
+    main27().await;
+}
+async fn main26() {
+    main27().await;
+    main28().await;
+}
+async fn main27() {
+    main28().await;
+    main29().await;
+}
+async fn main28() {
+    main29().await;
+    main30().await;
+}
+async fn main29() {
+    main30().await;
+    main31().await;
+}
+async fn main30() {
+    main31().await;
+    main32().await;
+}
+async fn main31() {
+    main32().await;
+    main33().await;
+}
+async fn main32() {
+    main33().await;
+    main34().await;
+}
+async fn main33() {
+    main34().await;
+    main35().await;
+}
+async fn main34() {
+    main35().await;
+    main36().await;
+}
+async fn main35() {
+    main36().await;
+    main37().await;
+}
+async fn main36() {
+    main37().await;
+    main38().await;
+}
+async fn main37() {
+    main38().await;
+    main39().await;
+}
+async fn main38() {
+    main39().await;
+    main40().await;
+}
+async fn main39() {
+    main40().await;
+}
+async fn main40() {
+    boom(&mut ()).await;
+}
+
+async fn boom(f: &mut ()) {}