Related "if/elsif" statements should not have the same condition

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.

Noncompliant Code Example

IF (param = 1) THEN
  open();
ELSIF (param = 2) THEN
  close();
ELSIF (param = 1) THEN // Incorrect
  move();
END IF;

Compliant Solution

IF (param = 1) THEN
  open();
ELSIF (param = 2) THEN
  close();
ELSIF (param = 3) THEN
  move();
END IF;