anchor.diff:  scalar Value
   scalar Bytes
   scalar Object
  -scalar AST
   scalar ByteOffset
   scalar FileIndex
   
  
positive.code: 
  type Contract {
    name: String
    source: Source
  }
  
  
negative.code: 
  type Compilation {
    compiler: Compiler!
    sources: [Source]!
    contracts: [SourceContract]!
  }
  
  type Compiler {
  