List.append_nil: law of bend-mathlib@0.8.1.0
Import: import bend-mathlib@0.8.1.0/list.bend as List
Lines 7-12 of bend-mathlib@0.8.1.0/list.bend: https://jend.leeeet.dev/read.txt?path=bend-mathlib@0.8.1.0/list.bend&start_line=7&end_line=12

import Base

# The empty list is a right identity for append: xs ++ [] = xs.
law append_nil:
  for -a: Quant
  for -A: Kind(a)
  for xs: List<a, A>
  {List.append(a, A, xs, Nil{}) == xs : List<a, A>}

Uses (2):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List.append