From a149ba26fa07b42b40f6e38f69ef74ecd756d68f Mon Sep 17 00:00:00 2001
From: Jason Newcomb <jsnewcomb@pm.me>
Date: Tue, 18 May 2021 10:51:59 -0400
Subject: [PATCH] Fix ICE in `implicit_return` async functions always return a
 value

---
 clippy_lints/src/implicit_return.rs |  6 +++++-
 tests/ui/crashes/ice-7231.rs        | 10 ++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 tests/ui/crashes/ice-7231.rs

diff --git a/clippy_lints/src/implicit_return.rs b/clippy_lints/src/implicit_return.rs
index 30174fa2100db..260a8f5015795 100644
--- a/clippy_lints/src/implicit_return.rs
+++ b/clippy_lints/src/implicit_return.rs
@@ -147,7 +147,11 @@ fn lint_implicit_returns(
             visit_break_exprs(block, |break_expr, dest, sub_expr| {
                 if dest.target_id.ok() == Some(expr.hir_id) {
                     if call_site_span.is_none() && break_expr.span.ctxt() == ctxt {
-                        lint_break(cx, break_expr.span, sub_expr.unwrap().span);
+                        // At this point sub_expr can be `None` in async functions which either diverge, or return the
+                        // unit type.
+                        if let Some(sub_expr) = sub_expr {
+                            lint_break(cx, break_expr.span, sub_expr.span);
+                        }
                     } else {
                         // the break expression is from a macro call, add a return to the loop
                         add_return = true;
diff --git a/tests/ui/crashes/ice-7231.rs b/tests/ui/crashes/ice-7231.rs
new file mode 100644
index 0000000000000..5595d8d1d6269
--- /dev/null
+++ b/tests/ui/crashes/ice-7231.rs
@@ -0,0 +1,10 @@
+// edition:2018
+#![allow(clippy::never_loop)]
+
+async fn f() {
+    loop {
+        break;
+    }
+}
+
+fn main() {}