== Why is this an issue?

A ``++case++`` and a chain of ``++if++``/``++elsif++`` statements is evaluated from top to bottom. At most, only one branch will be executed: the first one with a condition that evaluates to ``++true++``.


Therefore, duplicating a condition automatically leads to dead code. Usually, this is due to a copy/paste error. At best, it's simply dead code and at worst, it's a bug that is likely to induce further bugs as the code is maintained, and obviously it could lead to unexpected behavior.


For a ``++case++``, the second ``++when++`` will never be executed, rendering it dead code. Worse there is the risk in this situation that future maintenance will be done on the dead case, rather than on the one that's actually used.

=== Noncompliant code example

[source,ruby]
----
if param == 1
  openWindow()
elsif param == 2
  closeWindow()
elsif param == 1  # Noncompliant
  moveWindowToTheBackground()
end

case i
  when 1
    # ...
  when 3
    # ...
  when 1  # Noncompliant
    # ...
  else
    # ...
end
----

=== Compliant solution

[source,ruby]
----
if param == 1
  openWindow()
elsif param == 2
  closeWindow()
elsif param == 3
  moveWindowToTheBackground()
end

case i
  when 1
    # ...
  when 3
    # ...
  else
    # ...
end
----


ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

include::../message.adoc[]

include::../highlighting.adoc[]

'''
== Comments And Links
(visible only on this page)

include::../comments-and-links.adoc[]

endif::env-github,rspecator-view[]
