#include <cstdint>

struct Struct
{
    int16_t val;
};

int main()
{
        int16_t a = 0;
        //Struct b = {.val = a}; // No warning
        Struct b = {.val = a-1}; // Warning
        (void)b;
        return 0;
}

test.cpp: In function ‘int main()’:
test.cpp:12:29: warning: narrowing conversion of ‘(((int)a) + -1)’ from ‘int’ to ‘int16_t {aka short int}’ inside { } [-Wnarrowing]
         Struct b = {.val = a-1};
                             ^