List.nil_append_sym: law of bend-mathlib@0.8.1.0
Import: import bend-mathlib@0.8.1.0/list.bend as List
Lines 2138-2143 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=2138&end_line=2143

import Base

# The empty list is a left identity for append: [] ++ xs = xs, reversed to rewrite toward the simple side.
law nil_append_sym:
  for -a: Quant
  for -A: Kind(a)
  for -xs: List<a, A>
  {xs == List.append(a, A, Nil{}, xs) : List<a, A>}

Uses (4):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Equal.sym
  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
  https://jend.leeeet.dev/definition.txt?path=bend-mathlib@0.8.1.0/list.bend&name=nil_append