assigment to null class object member compiled? is this a bug?

[dangbinghoo via Digitalmars-d-learn]

hi,

why the code bellow compiles?
---
import std.stdio;
class A {
    int m;
}

void main() {
    A a;
    a.m = 1;
}
---

and running this code get:

`segmentation fault (core dumped)  ./test`

I consider this couldn't be compiled according to book <The D 
Programming Language>.

The latest dmd (2.082) and LDC2 behaves the same.