Synonym Family
ちゃんと言えば「Type Synonym Family」
型シノニム
に対する
TypeFamilies
の定義方法
以下の3つの総称
Open Type Synonym Family
Closed Type Synonym Family
Associated Type Family
https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/type_families.html#synonym-families