haskell-types.pegjs

// Haskell-Like Type Syntax
// for Fragment Editor
// ========================
//

start
    = Type
   
Type
    = NamedType / ArrayType / ObjectType

ObjectType
    = "{ " first:Field tail:(", " Field)* " }" { 
        return [first].concat(tail.map(it => it[1]))
            .reduce((v, acc) => Object.assign(v, acc), { _: 'object' });
    }
    
Field
    = key:FieldName " : " type:Type { 
        return { [key]: type }
    }

ArrayType 
    = "[" type:Type "]" {
        return { _: 'array', type }
    }

NamedType 
    = [a-zA-Z]+ {
        return { _: 'type', type: text() }
    }

FieldName
    = ([a-zA-Z][a-zA-Z0-9]*) {
        return text()
    }