Checks for silent narrowing conversions, e.g: int i = 0; i += 0.1;. While the issue is obvious in this former example, it might not be so in the following: void MyClass::f(double d) { int_member_ += d; }.

This rule is part of the “Expressions and statements” profile of the C++ Core Guidelines, corresponding to rule ES.46. See


We enforce only part of the guideline, more specifically, we flag:
  • All floating-point to integer conversions that are not marked by an explicit cast (c-style or static_cast). For example: int i = 0; i += 0.1;, void f(int); f(0.1);,
  • All applications of binary operators where the left-hand-side is an integer and the right-hand-size is a floating-point. For example: int i; i+= 0.1;.