anchor.diff:  
     visitBlockFunctionBody(BlockFunctionBody node) {
       // The "async" or "sync" keyword.
  -    if (node.keyword != null) {
  -      token(node.keyword);
  -      space();
  -    }
  +    token(node.keyword, followedBy: space);
   
       visit(node.block);
     }
  
positive.code:   }
  
    visitCatchClause(CatchClause node) {
  
      token(node.onKeyword, followedBy: space);
      visit(node.exceptionType);
  
  
negative.code: 
    visitExpressionFunctionBody(ExpressionFunctionBody node) {
      // The "async" or "sync" keyword.
      token(node.keyword, followedBy: space);
  
      int weight = lastSpaceWeight++;
      token(node.functionDefinition);
  