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diff --git a/src/test/ui/loops-reject-duplicate-labels-2.rs b/src/test/ui/loops-reject-duplicate-labels-2.rs
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+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(rustc_attrs)]
+
+// ignore-tidy-linelength
+
+// Issue #21633: reject duplicate loop labels in function bodies.
+//
+// This is testing the generalization (to the whole function body)
+// discussed here:
+// https://internals.rust-lang.org/t/psa-rejecting-duplicate-loop-labels/1833
+
+pub fn foo() {
+    { 'fl: for _ in 0..10 { break; } }   //~ NOTE first declared here
+    { 'fl: loop { break; } }             //~ WARN label name `'fl` shadows a label name that is already in scope
+    //~^ NOTE lifetime 'fl already in scope
+    { 'lf: loop { break; } }             //~ NOTE first declared here
+    { 'lf: for _ in 0..10 { break; } }   //~ WARN label name `'lf` shadows a label name that is already in scope
+    //~^ NOTE lifetime 'lf already in scope
+    { 'wl: while 2 > 1 { break; } }      //~ NOTE first declared here
+    { 'wl: loop { break; } }             //~ WARN label name `'wl` shadows a label name that is already in scope
+    //~^ NOTE lifetime 'wl already in scope
+    { 'lw: loop { break; } }             //~ NOTE first declared here
+    { 'lw: while 2 > 1 { break; } }      //~ WARN label name `'lw` shadows a label name that is already in scope
+    //~^ NOTE lifetime 'lw already in scope
+    { 'fw: for _ in 0..10 { break; } }   //~ NOTE first declared here
+    { 'fw: while 2 > 1 { break; } }      //~ WARN label name `'fw` shadows a label name that is already in scope
+    //~^ NOTE lifetime 'fw already in scope
+    { 'wf: while 2 > 1 { break; } }      //~ NOTE first declared here
+    { 'wf: for _ in 0..10 { break; } }   //~ WARN label name `'wf` shadows a label name that is already in scope
+    //~^ NOTE lifetime 'wf already in scope
+    { 'tl: while let Some(_) = None::<i32> { break; } } //~ NOTE first declared here
+    { 'tl: loop { break; } }             //~ WARN label name `'tl` shadows a label name that is already in scope
+    //~^ NOTE lifetime 'tl already in scope
+    { 'lt: loop { break; } }             //~ NOTE first declared here
+    { 'lt: while let Some(_) = None::<i32> { break; } }
+                                         //~^ WARN label name `'lt` shadows a label name that is already in scope
+                                         //~| NOTE lifetime 'lt already in scope
+}
+
+#[rustc_error]
+pub fn main() { //~ ERROR compilation successful
+    foo();
+}