layout toplevel ;

entrypoints [Def], Exp ;

token Id ((letter|digit|["[]_"])+) ;

comment "--" ;
comment "{-" "-}" ;

TypeDef. Def ::= "type" TypeSig1 "|" [Decl] ;
VarDef.  Def ::= Id ":" TypeSig ":=" Exp ;
separator Def ";" ;

Decl. Decl ::= Id ":" TypeSig ;
separator nonempty Decl "|" ;

TypeFun. TypeSig  ::= TypeSig1 "→"  TypeSig ;
TypeApp. TypeSig1 ::= Id [TypeSig2] ;
TypeVar. TypeSig2 ::= Id ;
coercions TypeSig 2;

separator nonempty TypeSig2 "" ;

ExpTyped. Exp  ::= Exp1 ":" TypeSig ;
ExpAbs.   Exp1 ::= "λ" [Id] "." Exp2 ;
ExpApp.   Exp2 ::= Exp3 [Exp3] ;
ExpVar.   Exp3 ::= Id ;

separator nonempty Exp3 "" ;
coercions Exp 3;

separator nonempty Id "" ;