title: What is the concept of "weak conformance" in Scala?
body: <p>I just recently encountered the term "Weak Conformance" (in Stack Overflow user <a href="https://stackoverflow.com/users/160378/retronym">retronym</a>'s answer to <em><a href="https://stackoverflow.com/questions/3088979/how-to-set-up-implicit-conversion-to-allow-arithmetic-between-numeric-types">How to set up implicit conversion to allow arithmetic between numeric types?</a></em>).</p>
  
  <p>What is it?</p>