homoiconity is your program as data structure

debugger is utilities for stepping through program

data Haskell
  = Module ModuleName [Export]
  | Datatype TypeName [Constructor]
  | Alias TypeName Type
  | Newtype TypeName Type
  | Class ClassName ClassContext ...
  | Instance ClassName ...
  | Claim Name
  | Clause Name [Pattern] Expression
  | Where [Binding]

type Name = Ident
type ModuleName = [Ident]
data TypeName = TypeName Ident [Ident]
data ClassName = ClassName Ident [Constraint] [Ident]

data Export ...

data Constructor ...

data Pattern ...
data PatternGuard = PatternG Pattern Expression

data Expression
  = If Expression Expression Expression
  | Case Expression [PatternGuard]
  | Let [Binding] Expression
  | App Ident [Expression]