From 1013ee8df512015855937615500690664399545f Mon Sep 17 00:00:00 2001
From: Gary Guo <gary@garyguo.net>
Date: Fri, 4 Nov 2022 03:08:28 +0000
Subject: [PATCH] Fix ICE when negative impl is collected during eager mono

---
 compiler/rustc_monomorphize/src/collector.rs    |  4 ++++
 src/test/ui/traits/negative-impls/eager-mono.rs | 12 ++++++++++++
 2 files changed, 16 insertions(+)
 create mode 100644 src/test/ui/traits/negative-impls/eager-mono.rs

diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index 3cfddd75462c0..58ddb807059ae 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -1336,6 +1336,10 @@ fn create_mono_items_for_default_impls<'tcx>(
 ) {
     match item.kind {
         hir::ItemKind::Impl(ref impl_) => {
+            if matches!(impl_.polarity, hir::ImplPolarity::Negative(_)) {
+                return;
+            }
+
             for param in impl_.generics.params {
                 match param.kind {
                     hir::GenericParamKind::Lifetime { .. } => {}
diff --git a/src/test/ui/traits/negative-impls/eager-mono.rs b/src/test/ui/traits/negative-impls/eager-mono.rs
new file mode 100644
index 0000000000000..ce770376c0b2f
--- /dev/null
+++ b/src/test/ui/traits/negative-impls/eager-mono.rs
@@ -0,0 +1,12 @@
+// build-pass
+// compile-flags:-C link-dead-code=y
+
+#![feature(negative_impls)]
+
+trait Foo {
+    fn foo() {}
+}
+
+impl !Foo for () {}
+
+fn main() {}