Format label break

src/expr.rs

@@ -118,19 +118,19 @@ pub fn format_expr(
         | ast::ExprKind::While(..)
         | ast::ExprKind::WhileLet(..) => to_control_flow(expr, expr_type)
             .and_then(|control_flow| control_flow.rewrite(context, shape)),
-        // FIXME(topecongiro): Handle label on a block (#2722).
-        ast::ExprKind::Block(ref block, _) => {
+        ast::ExprKind::Block(ref block, opt_label) => {
             match expr_type {
                 ExprType::Statement => {
                     if is_unsafe_block(block) {
-                        rewrite_block(block, Some(&expr.attrs), context, shape)
+                        rewrite_block(block, Some(&expr.attrs), opt_label, context, shape)
                     } else if let rw @ Some(_) =
                         rewrite_empty_block(context, block, Some(&expr.attrs), "", shape)
                     {
                         // Rewrite block without trying to put it in a single line.
                         rw
                     } else {
                         let prefix = block_prefix(context, block, shape)?;
+
                         rewrite_block_with_visitor(
                             context,
                             &prefix,
@@ -141,7 +141,9 @@ pub fn format_expr(
                         )
                     }
                 }
-                ExprType::SubExpression => rewrite_block(block, Some(&expr.attrs), context, shape),
+                ExprType::SubExpression => {
+                    rewrite_block(block, Some(&expr.attrs), opt_label, context, shape)
+                }
             }
         }
         ast::ExprKind::Match(ref cond, ref arms) => {
@@ -327,6 +329,7 @@ pub fn format_expr(
                     rewrite_block(
                         block,
                         Some(&expr.attrs),
+                        None,
                         context,
                         Shape::legacy(budget, shape.indent)
                     )?
@@ -644,17 +647,20 @@ pub fn rewrite_block_with_visitor(
 
 impl Rewrite for ast::Block {
     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
-        rewrite_block(self, None, context, shape)
+        rewrite_block(self, None, None, context, shape)
     }
 }
 
 fn rewrite_block(
     block: &ast::Block,
     attrs: Option<&[ast::Attribute]>,
+    label: Option<ast::Label>,
     context: &RewriteContext,
     shape: Shape,
 ) -> Option<String> {
-    let prefix = block_prefix(context, block, shape)?;
+    let unsafe_string = block_prefix(context, block, shape)?;
+    let label_string = rewrite_label(label);
+    let prefix = format!("{}{}", unsafe_string, label_string);
 
     // shape.width is used only for the single line case: either the empty block `{}`,
     // or an unsafe expression `unsafe { e }`.

tests/source/label_break.rs

@@ -0,0 +1,28 @@
+// format with label break value.
+fn main() {
+
+'empty_block: {}
+
+'block: {
+    do_thing();
+    if condition_not_met() {
+        break 'block;
+    }
+    do_next_thing();
+    if condition_not_met() {
+        break 'block;
+    }
+    do_last_thing();
+}
+
+let result = 'block: {
+    if foo() {
+        // comment
+        break 'block       1;
+    }
+    if bar() { /* comment */
+        break 'block      2;
+    }
+    3
+};
+}

tests/target/label_break.rs

@@ -0,0 +1,28 @@
+// format with label break value.
+fn main() {
+    {}
+
+    {
+        do_thing();
+        if condition_not_met() {
+            break 'block;
+        }
+        do_next_thing();
+        if condition_not_met() {
+            break 'block;
+        }
+        do_last_thing();
+    }
+
+    let result = 'block: {
+        if foo() {
+            // comment
+            break 'block 1;
+        }
+        if bar() {
+            /* comment */
+            break 'block 2;
+        }
+        3
+    };
+}