Feature.duplicates: def of bendvy-ecs-core@0.1.0.4
Import: import bendvy-ecs-core@0.1.0.4/feature.bend as Feature
Lines 57-60 of bendvy-ecs-core@0.1.0.4/feature.bend: https://jend.leeeet.dev/read.txt?path=bendvy-ecs-core@0.1.0.4/feature.bend&start_line=57&end_line=60

import Base

def duplicates(items:List<&2,String>,+seen:List<&2,String>) -> Validation:
  match items:
    case []: Valid{}
    case +name <> rest: repeated(contains(seen,name),name,_ => duplicates(rest,name <> seen))

Uses (5):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=String
  https://jend.leeeet.dev/definition.txt?path=bendvy-ecs-core@0.1.0.4/feature.bend&name=Validation
  https://jend.leeeet.dev/definition.txt?path=bendvy-ecs-core@0.1.0.4/feature.bend&name=contains
  https://jend.leeeet.dev/definition.txt?path=bendvy-ecs-core@0.1.0.4/feature.bend&name=repeated