From 6f78e6265a6b43ea53abf048efa688fa0cdb33d9 Mon Sep 17 00:00:00 2001
From: Bryanskiy <ivakin.kir@gmail.com>
Date: Mon, 10 Jun 2024 21:21:46 +0300
Subject: [PATCH] Delegation: fix ICE on recursive delegation

---
 compiler/rustc_ast_lowering/src/delegation.rs |  4 +++-
 tests/crashes/124347.rs                       |  4 ----
 tests/ui/delegation/ice-issue-124347.rs       | 12 ++++++++++++
 tests/ui/delegation/ice-issue-124347.stderr   | 14 ++++++++++++++
 4 files changed, 29 insertions(+), 5 deletions(-)
 delete mode 100644 tests/crashes/124347.rs
 create mode 100644 tests/ui/delegation/ice-issue-124347.rs
 create mode 100644 tests/ui/delegation/ice-issue-124347.stderr

diff --git a/compiler/rustc_ast_lowering/src/delegation.rs b/compiler/rustc_ast_lowering/src/delegation.rs
index 27f8a6eae02a9..d9dd0b3bca534 100644
--- a/compiler/rustc_ast_lowering/src/delegation.rs
+++ b/compiler/rustc_ast_lowering/src/delegation.rs
@@ -67,7 +67,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
             return false;
         };
         if let Some(local_sig_id) = sig_id.as_local() {
-            self.resolver.delegation_fn_sigs[&local_sig_id].has_self
+            // The value may be missing due to recursive delegation.
+            // Error will be emmited later during HIR ty lowering.
+            self.resolver.delegation_fn_sigs.get(&local_sig_id).map_or(false, |sig| sig.has_self)
         } else {
             match self.tcx.def_kind(sig_id) {
                 DefKind::Fn => false,
diff --git a/tests/crashes/124347.rs b/tests/crashes/124347.rs
deleted file mode 100644
index d2bc555fe1c7b..0000000000000
--- a/tests/crashes/124347.rs
+++ /dev/null
@@ -1,4 +0,0 @@
-//@ known-bug: #124347
-trait Trait: ToReuse {
-    reuse Trait::lolno { &self.0 };
-}
diff --git a/tests/ui/delegation/ice-issue-124347.rs b/tests/ui/delegation/ice-issue-124347.rs
new file mode 100644
index 0000000000000..82a96055099c7
--- /dev/null
+++ b/tests/ui/delegation/ice-issue-124347.rs
@@ -0,0 +1,12 @@
+#![feature(fn_delegation)]
+#![allow(incomplete_features)]
+
+trait Trait {
+    reuse Trait::foo { &self.0 }
+    //~^ ERROR recursive delegation is not supported yet
+}
+
+reuse foo;
+//~^ ERROR recursive delegation is not supported yet
+
+fn main() {}
diff --git a/tests/ui/delegation/ice-issue-124347.stderr b/tests/ui/delegation/ice-issue-124347.stderr
new file mode 100644
index 0000000000000..5a3f4525d29e5
--- /dev/null
+++ b/tests/ui/delegation/ice-issue-124347.stderr
@@ -0,0 +1,14 @@
+error: recursive delegation is not supported yet
+  --> $DIR/ice-issue-124347.rs:5:18
+   |
+LL |     reuse Trait::foo { &self.0 }
+   |                  ^^^ callee defined here
+
+error: recursive delegation is not supported yet
+  --> $DIR/ice-issue-124347.rs:9:7
+   |
+LL | reuse foo;
+   |       ^^^ callee defined here
+
+error: aborting due to 2 previous errors
+