Using "alias const(some_type) some_alias;" produces an alias for some_type instead of being an alias for const(some_type) for user-defined types. The following code demonstrates:
-----
struct Foo { }
typedef int Bar;
alias const( int ) CONST_INT;
alias const( int )[] INT_ARRAY;
alias const( Bar ) CONST_BAR;
alias const( Foo ) CONST_FOO;
alias const( Object ) CONST_OBJECT;
alias const( Object )[] OBJ_ARRAY;
pragma( msg, CONST_INT.stringof ); // prints const int; should be const(int) ?
pragma( msg, INT_ARRAY.stringof ); // prints const(int)[]; correct.
pragma( msg, CONST_BAR.stringof ); // prints Bar; should be const(Bar)
pragma( msg, CONST_FOO.stringof ); // prints Foo; should be const(Foo)
pragma( msg, CONST_OBJECT.stringof ); // prints Object; should print const(Object)
pragma( msg, OBJ_ARRAY.stringof ); // prints const(Object)[]; correct.

/* Copy/pasted compiler output from DMD 2.003:
const int
const(int)[]
Bar
Foo
Object
const(Object)[]
*/