Example

class MyClass {
public:
MyClass& operator=(const MyClass& rhs);

private:
int field;
};

MyClass& MyClass::operator=(const MyClass& rightValue)
{
if(rightValue.field == this.field){
return rightValue;
}
}

Solution

Return *this from the assignment operator.

class MyClass {
public:
MyClass& operator=(const MyClass& rhs);

private:
int field;
};

MyClass& MyClass::operator=(const MyClass& rightValue)
{
if(rightValue.field == this.field){
return *this;
}
}