Don't make a void arrow function.

utils/pub/yaml/parser.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Translates a string of characters into a YAML serialization tree.
  *
  * This parser is designed to closely follow the spec. All productions in the
  * spec are numbered, and the corresponding methods in the parser have the same
  * numbers. This is certainly not the most efficient way of parsing YAML, but it
@@ skipping 1430 matching lines @@
     case CHOMPING_CLIP:
       l_stripEmpty(indent);
       break;
     case CHOMPING_KEEP:
       l_keepEmpty(indent);
       break;
     }
   }
 
   // 167
-  void l_stripEmpty(int indent) => captureAs('', () {
-    zeroOrMore(() => transaction(() {
-        if (!truth(s_indentLessThanOrEqualTo(indent))) return false;
-        return b_nonContent();
-      }));
-    zeroOrOne(() => l_trailComments(indent));
-    return true;
-  });
+  void l_stripEmpty(int indent) {
+    captureAs('', () {
+      zeroOrMore(() => transaction(() {
+          if (!truth(s_indentLessThanOrEqualTo(indent))) return false;
+          return b_nonContent();
+        }));
+      zeroOrOne(() => l_trailComments(indent));
+      return true;
+    });
+  }
 
   // 168
   void l_keepEmpty(int indent) {
     zeroOrMore(() => captureAs('\n', () => l_empty(indent, BLOCK_IN)));
     zeroOrOne(() => captureAs('', () => l_trailComments(indent)));
   }
 
   // 169
   bool l_trailComments(int indent) => transaction(() {
     if (!truth(s_indentLessThanOrEqualTo(indent))) return false;
@@ skipping 420 matching lines @@
 
 /** The information in the header for a block scalar. */
 class _BlockHeader {
   final int additionalIndent;
   final int chomping;
 
   _BlockHeader(this.additionalIndent, this.chomping);
 
   bool get autoDetectIndent() => additionalIndent == null;
 }