Add test of parenthesizing break value by AST pretty-printer

Author: dtolnay

tests/ui/unpretty/expanded-interpolation.rs

@@ -18,6 +18,26 @@ macro_rules! stmt {
     ($stmt:stmt) => { $stmt };
 }
 
+fn break_labeled_loop() {
+    let no_paren = 'outer: loop {
+        break 'outer expr!('inner: loop { break 'inner 1; } + 1);
+    };
+
+    let paren_around_break_value = 'outer: loop {
+        break expr!('inner: loop { break 'inner 1; } + 1);
+    };
+
+    macro_rules! breaking {
+        ($value:expr) => {
+            break $value
+        };
+    }
+
+    let paren_around_break_value = loop {
+        breaking!('inner: loop { break 'inner 1; } + 1);
+    };
+}
+
 fn if_let() {
     macro_rules! if_let {
         ($pat:pat, $expr:expr) => {

tests/ui/unpretty/expanded-interpolation.stdout

@@ -20,6 +20,19 @@ macro_rules! expr { ($expr:expr) => { $expr }; }
 
 macro_rules! stmt { ($stmt:stmt) => { $stmt }; }
 
+fn break_labeled_loop() {
+    let no_paren =
+        'outer: loop { break 'outer 'inner: loop { break 'inner 1; } + 1; };
+
+    let paren_around_break_value =
+        'outer: loop { break 'inner: loop { break 'inner 1; } + 1; };
+
+    macro_rules! breaking { ($value:expr) => { break $value }; }
+
+    let paren_around_break_value =
+        loop { break 'inner: loop { break 'inner 1; } + 1; };
+}
+
 fn if_let() {
     macro_rules! if_let {
         ($pat:pat, $expr:expr) => { if let $pat = $expr {} };