Wildcard:
    Identifier ":" TypeExpr ("*"?)
TypeExpr:
    BinaryExpr

BinaryExpr: 
    UnaryExpr { Operator PrimitiveExpr }*

UnaryExpr:
    {UnaryOperator}? PrimitiveExpr

PrimitiveExpr:
    GroupExpr | Identifier

GroupExpr:
    "(" TypeExpr ")"