The "code" is `a + b`. The rest is just decorations.

Here's example from article:

    static int f(int a, int b)
    {
     x = b ? 42 : 43;
 return a/b;
    }

So you expect the compiler to tell you every time it inlines a function with a null check in a function which already had a null check on the same value?

Because as far as it’s concerned that is the same thing.

Both clang-tidy and sonar will flag this since it’s broken on its own, but when you’ve fixed it you want the compiler to warn you every time this is inlined in a function where b is known non-zero and the check is redundant?

As flo told you, if you want a non-optimizing compiler use a non-optimizing compiler.