String.nil_append: law of bend-mathlib@0.8.1.0
Import: import bend-mathlib@0.8.1.0/string.bend as String
Lines 27-30 of bend-mathlib@0.8.1.0/string.bend: https://jend.leeeet.dev/read.txt?path=bend-mathlib@0.8.1.0/string.bend&start_line=27&end_line=30

import Base

# The empty string is a left identity for append: "" ++ a = a.
law nil_append:
  for -a: String
  {String.append(SNil{}, a) == a : String}

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