Don't define a default constructor that only initializes data members; use default member initializers instead

Reason

Using default member initializers lets the compiler generate the function for you. The compiler-generated function can be more efficient.

Example, bad

class X1 { // BAD: doesn't use member initializers
    string s;
    int i;
public:
    X1() :s{"default"}, i{1} { }
    // ...
};

Example

class X2 {
    string s {"default"};
    int i {1};
public:
    // use compiler-generated default constructor
    // ...
};

Enforcement

(Simple) Flag if a default constructor's explicit member initializer is a constant, and recommend that the constant should be written as a data member initializer instead.