Assignments within sub-expressions are hard to spot and therefore make the code less readable.

It is also a common mistake to write = when == was meant.

Ideally, expressions should not have side-effects.

Noncompliant Code Example

doSomething(i = 42);

Compliant Solution

i = 42;
doSomething(i);

or

doSomething(i == 42);  // Perhaps in fact the assignment operator was expected

Exceptions

Assignments in while statement conditions, and assignments enclosed in relational expressions are allowed.

See