Having two ``cases`` in a ``match`` statement or two branches in an ``if`` chain  with the same implementation is at best duplicate code, and at worst a coding error. If the same logic is truly needed for both instances, then in an ``if`` chain they should be combined, or for a ``match``, one should fall through to the other. 

== Noncompliant Code Example

----
value match {
  case 1 =>
    doFirstThing
    doSomething
  case 2 =>
    doSomethingDifferent
  case 3 => // Noncompliant; duplicates case 1's implementation
    doFirstThing
    doSomething
  case _ =>
    doTheRest
}

if (a >= 0 && a < 10) {
  doFirstThing
  doTheThing
}
else if (a >= 10 && a < 20) {
  doTheOtherThing
}
else if (a >= 20 && a < 50) {
  doFirstThing
  doTheThing  // Noncompliant; duplicates first condition
}
else {
  doTheRest
}
----

== Exceptions

Blocks in an ``if`` chain that contain a single line of code are ignored, as are blocks in a ``match`` statement that contain a single line of code.

----
if(a == 1) {
  doSomething  //no issue, usually this is done on purpose to increase the readability
} else if (a == 2) {
  doSomethingElse
} else {
  doSomething
}
----

But this exception does not apply to ``if`` chains without ``else``-s, or to ``match``-es without default clauses when all branches have the same single line of code. In case of ``if`` chains with ``else``-s, or of ``match``-es with default clauses, rule S3923 raises a bug. 

----
if(a == 1) {
  doSomething  //Noncompliant, this might have been done on purpose but probably not
} else if (a == 2) {
  doSomething
}
----