     case .Alias:
       let m = advance().match
       let name = m.substringFromIndex(m.startIndex.successor())
-      return aliases[name] ?? .Invalid("unknown alias \(name), \(context(buildContext()))")
+      return aliases[name] ?? .Invalid("unknown alias \(name), \(buildContext())")
 
     case .End:
       return .Null
 
     default:
-      return .Invalid("unexpected type \(peek().type), \(context(buildContext()))")
+      return .Invalid("unexpected type \(peek().type), \(buildContext())")
 
     }
   }

      let invalidPattern = /"^( {0,\(foundIndent)}\\n)* {\(foundIndent + 1),}"
      if block ~ invalidPattern {
        return .Invalid(
            "leading all-space line must not have to many spaces, \(context(buildContext()))")
      }
    }
    if indent > 0 && foundIndent < indent {
      return .Invalid(
          "less indented block scalar than the indicated level, \(context(buildContext()))")
    } else if indent == 0 {
      indent = foundIndent
    }

        break
      }
    }
    return context(text)
  }

  func ignoreSpace () {
