Using the same value on either side of a binary operator is almost always a mistake. In the case of logical operators, it is either a copy/paste
error and therefore a bug, or it is simply wasted code, and should be simplified. In the case of bitwise operators and most binary mathematical
operators, having the same value on both sides of an operator yields predictable results, and should be simplified.
This rule ignores *, +.
Noncompliant code example
if a == a { // always true
doZ()
}
if a != a { // always false
doY()
}
if a == b && a == b { // if the first one is true, the second one is too
doX()
}
if a == b || a == b { // if the first one is true, the second one is too
doW()
}
var j = 5 / 5 //always 1
var k = 5 - 5 //always 0
Exceptions
Left-shifting 1 onto 1 is common in the construction of bit masks, and is ignored.
var i = 1 << 1; // Compliant
var j = a << a; // Noncompliant
