safety: null checks

[Paul Backus]

On Monday, 23 November 2020 at 00:26:26 UTC, Dibyendu Majumdar 
wrote:
>
> Hmm, null values are not the same as dereferncing null values.
> A null in itself is okay, but dereferencing null cannot be.

@safe code is allowed to dereference pointers, and there's no way 
for the compiler to know at compile time which pointers are null 
and which aren't. So, either @safe code must be forbidden from 
creating null pointers in the first place, or it must be allowed 
to dereference them.

Remember, @safe doesn't just mean "code that's memory safe", it 
means "code that the compiler can *prove* is memory safe."