data Module
  | Module "module" uident ImportList DefineList

data Import | Import "import" uident

data Define
  | Define "define" Type lident "(" TVarList ")" "=" "{" StmtList "}"

data Stmt
  | LetS TVar "=" Exp
  | StoreS TVar ":=" Atom
  | CallS "call" TVar "(" AtomList ")"
  | SwitchS "switch" Atom "{" StmtList "}" "{" SwitchAltList "}"
  | IfS "if" Atom "{" StmtList "}"  "{" StmtList "}"
  | WhenS "when" Atom "{" StmtList "}"
  | WhileS "while" "{" StmtList "}" Atom "{" StmtList "}"
  | ReturnS "return" Atom
  | NoOpS "noop"

data Exp
  | CallE TVar "(" AtomList ")"
  | CastE "cast" TVar Type
  | AllocaE "alloca" Type
  | LoadE "load" "(" TVar ")"
  | AtomE Atom

data Atom
  | LitA TLit
  | VarA TVar

data SwitchAlt | SwitchAlt TLit "->" "{" StmtList "}"

data Lit
  | StringL string
  | NmbrL number
  | CharL char
  | EnumL uident
  | VoidL

data TyDecl
  | TyEnum "enum" EnumCList
  -- | TyArray "[" integer "]" Type
  | TyRecord "record" "{" FieldTList "}"
  | TyTagged "tagged" ConCList

data TVar | TVar lident "::" Type

data TLit | TLit Lit "::" Type

data FieldT | FieldT uident "::" Type

data ConC | ConC uident Type

data Type | Type uident "(" TypeList ")"

data EnumC | EnumC uident

list ConCList ConC nonempty separator "|" horiz
list FieldTList FieldT nonempty separator "," horiz
list EnumCList EnumC nonempty separator "|" horiz
list TypeList Type empty separator "," horiz
list ExpList Exp nonempty separator "," horiz
list AtomList Atom nonempty separator "," horiz
list TVarList TVar nonempty separator "," horiz
list SwitchAltList SwitchAlt empty terminator ";" vert
list StmtList Stmt empty terminator ";" vert
list DefineList Define empty terminator ";" vert
list ImportList Import empty terminator ";" vert