From 91dcbbbf50baa02d0757085bb5a9bd69bae5a5a4 Mon Sep 17 00:00:00 2001
From: Samrat Man Singh <samratmansingh@gmail.com>
Date: Mon, 25 May 2020 20:45:26 +0530
Subject: [PATCH] Allow unlabeled breaks from desugared `?` in labeled blocks

---
 src/librustc_passes/loops.rs                         |  3 ++-
 .../ui/label/label_break_value_desugared_break.rs    | 12 ++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)
 create mode 100644 src/test/ui/label/label_break_value_desugared_break.rs

diff --git a/src/librustc_passes/loops.rs b/src/librustc_passes/loops.rs
index 09b3d44020d..767a6909d31 100644
--- a/src/librustc_passes/loops.rs
+++ b/src/librustc_passes/loops.rs
@@ -9,6 +9,7 @@ use rustc_middle::hir::map::Map;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
+use rustc_span::hygiene::DesugaringKind;
 use rustc_span::Span;
 
 #[derive(Clone, Copy, Debug, PartialEq)]
@@ -203,7 +204,7 @@ impl<'a, 'hir> CheckLoopVisitor<'a, 'hir> {
         label: &Destination,
         cf_type: &str,
     ) -> bool {
-        if self.cx == LabeledBlock {
+        if !span.is_desugaring(DesugaringKind::QuestionMark) && self.cx == LabeledBlock {
             if label.label.is_none() {
                 struct_span_err!(
                     self.sess,
diff --git a/src/test/ui/label/label_break_value_desugared_break.rs b/src/test/ui/label/label_break_value_desugared_break.rs
new file mode 100644
index 00000000000..de883b61111
--- /dev/null
+++ b/src/test/ui/label/label_break_value_desugared_break.rs
@@ -0,0 +1,12 @@
+// compile-flags: --edition 2018
+#![feature(label_break_value, try_blocks)]
+
+// run-pass
+fn main() {
+    let _: Result<(), ()> = try {
+        'foo: {
+            Err(())?;
+            break 'foo;
+        }
+    };
+}