A few questions

[Namespace]

1.
Why are these two method header identitcal?

const Foo some_function() {

and

Foo some_function() const {

?

IMO that isn't consistent. IMO only the last is valid.
With this example, it is somewhat understandable.

// C++
class Bar {
     const Foo getFooObj() const { ... }
     const Foo& getFooObjRef const { ... }
};

// D
class Bar {
     const(Foo) getFooObj() const { ... }
     ref Foo getObjRef() { ... }
}

const(Foo) but ref Foo. This is inconsistency, if you ask me.
So why is between C++ and D such a huge difference?
Why isn't it simply const Foo instead of const(Foo)?

2.
What's about a shorthand for debug assertions?
E.g. to avoid not-null references (yes, if you're a windows user, 
you hate them):

Example:

[code]
void some_function(Foo !f) {
[/code]

will automatically converted by the compiler into:

[code]
void some_function(Foo f, string filename = __FILE__, uint line = 
__LINE__) in {
     assert(f !is null, format("Null Object @ file %s on line 
%d.", filename, line));
} body {
[/code]

That would be avoid many many efforts by writing safe code. And 
it avoids Java code stil with explizit pre- and postconditions 
which blows up code.