What makes Haskell's type system more "powerful" than other languages' type systems? -

reading disadvantages of scala type system versus haskell?, have ask: it, specifically, makes haskell's type system more powerful other languages' type systems (c, c++, java). apparently, scala can't perform of same powers haskell's type system. it, specifically, makes haskell's type system (hindley–milner type inference) powerful? can give example?

what it, specifically, makes haskell's type system

it has been engineered past decade both flexible -- logic property verification -- , powerful.

haskell's type system has been developed on years encourage relatively flexible, expressive static checking discipline, several groups of researchers identifying type system techniques enable powerful new classes of compile-time verification. scala's relatively undeveloped in area.

that is, haskell/ghc provides logic both powerful , designed encourage type level programming. unique in world of functional programming.

some papers give flavor of direction engineering effort on haskell's type system has taken:

• fun type functions
• associated types class
• fun functional dependencies