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