invariant_booleans

Group: errors

Maturity: experimental

Linter v0.1.25

Since info is static, may be stale

View all Lint Rules

Using the Linter

DON'T test for conditions that can be inferred at compile time or test the same condition twice.

Conditional statements using a condition which cannot be anything but false have the effect of making blocks of code non-functional. If the condition cannot evaluate to anything but true, the conditional statement is completely redundant, and makes the code less readable. It is quite likely that the code does not match the programmer's intent. Either the condition should be removed or it should be updated so that it does not always evaluate to true or false and does not perform redundant tests. This rule will hint to the test conflicting with the linted one.

BAD:

// foo can't be both equal and not equal to bar in the same expression
if(foo == bar && something && foo != bar) {...}

BAD:

void compute(int foo) {
  if (foo == 4) {
    doSomething();
    // we know foo is equal to 4 at this point, so the next condition is always false
    if (foo > 4) {...}
    ...
  }
  ...
}

BAD:

void compute(bool foo) {
  if (foo) {
    return;
  }
  doSomething();
  // foo is always false here
  if (foo){...}
  ...
}

GOOD:

void nestedOK() {
  if (foo == bar) {
    foo = baz;
    if (foo != bar) {...}
  }
}

GOOD:

void nestedOk2() {
  if (foo == bar) {
    return;
  }

  foo = baz;
  if (foo == bar) {...} // OK
}

GOOD:

void nestedOk5() {
  if (foo != null) {
    if (bar != null) {
      return;
    }
  }

  if (bar != null) {...} // OK
}