fix the visitor's starting position when visiting a labelled block

Close #3217

src/expr.rs

@@ -417,15 +417,16 @@ fn rewrite_empty_block(
     prefix: &str,
     shape: Shape,
 ) -> Option<String> {
+    if !block.stmts.is_empty() {
+        return None;
+    }
+
     let label_str = rewrite_label(label);
     if attrs.map_or(false, |a| !inner_attributes(a).is_empty()) {
         return None;
     }
 
-    if block.stmts.is_empty()
-        && !block_contains_comment(block, context.source_map)
-        && shape.width >= 2
-    {
+    if !block_contains_comment(block, context.source_map) && shape.width >= 2 {
         return Some(format!("{}{}{{}}", prefix, label_str));
     }
 
@@ -510,13 +511,13 @@ pub fn rewrite_block_with_visitor(
     let mut visitor = FmtVisitor::from_context(context);
     visitor.block_indent = shape.indent;
     visitor.is_if_else_block = context.is_if_else_block();
-    match block.rules {
-        ast::BlockCheckMode::Unsafe(..) => {
+    match (block.rules, label) {
+        (ast::BlockCheckMode::Unsafe(..), _) | (ast::BlockCheckMode::Default, Some(_)) => {
             let snippet = context.snippet(block.span);
             let open_pos = snippet.find_uncommented("{")?;
             visitor.last_pos = block.span.lo() + BytePos(open_pos as u32)
         }
-        ast::BlockCheckMode::Default => visitor.last_pos = block.span.lo(),
+        (ast::BlockCheckMode::Default, None) => visitor.last_pos = block.span.lo(),
     }
 
     let inner_attrs = attrs.map(inner_attributes);

src/reorder.rs

@@ -42,10 +42,8 @@ fn compare_items(a: &ast::Item, b: &ast::Item) -> Ordering {
         (&ast::ItemKind::ExternCrate(ref a_name), &ast::ItemKind::ExternCrate(ref b_name)) => {
             // `extern crate foo as bar;`
             //               ^^^ Comparing this.
-            let a_orig_name =
-                a_name.map_or_else(|| a.ident.as_str(), |symbol| symbol.as_str());
-            let b_orig_name =
-                b_name.map_or_else(|| b.ident.as_str(), |symbol| symbol.as_str());
+            let a_orig_name = a_name.map_or_else(|| a.ident.as_str(), |symbol| symbol.as_str());
+            let b_orig_name = b_name.map_or_else(|| b.ident.as_str(), |symbol| symbol.as_str());
             let result = a_orig_name.cmp(&b_orig_name);
             if result != Ordering::Equal {
                 return result;

tests/source/issue-3217.rs

@@ -0,0 +1,8 @@
+#![feature(label_break_value)]
+
+fn main() {
+    let mut res = 0;
+    's_39: { if res == 0i32 { println!("Hello, world!"); } }
+    's_40: loop { println!("res = {}", res); res += 1; if res == 3i32 { break 's_40; } }
+    let toto = || { if true { 42 } else { 24 } };
+}

tests/target/issue-3217.rs

@@ -0,0 +1,24 @@
+#![feature(label_break_value)]
+
+fn main() {
+    let mut res = 0;
+    's_39: {
+        if res == 0i32 {
+            println!("Hello, world!");
+        }
+    }
+    's_40: loop {
+        println!("res = {}", res);
+        res += 1;
+        if res == 3i32 {
+            break 's_40;
+        }
+    }
+    let toto = || {
+        if true {
+            42
+        } else {
+            24
+        }
+    };
+}