Consider this simple example
A)-----------------------------------------
struct StaticRegister {
static private uint _value;
@property static uint value() { return _value; }
@property static void value(uint v) { _value = v; }
}
void main(string[] s) {
StaticRegister = 1;
assert(StaticRegister == 1);
}
-------------------------------------------
This gives two errors for each line in `main` (exactly what I
expected).
test.d(8): Error: StaticRegister is not an lvalue
test.d(9): Error: incompatible types for ((StaticRegister) ==
(1)):
cannot use '==' with types
However, if I modify the example by adding an `alias this` ...
B)-----------------------------------------
struct StaticRegister {
static private uint _value;
@property static uint value() { return _value; }
@property static void value(uint v) { _value = v; }
alias value this;
}
void main(string[] s) {
StaticRegister = 1;
assert(StaticRegister == 1);
}
-------------------------------------------
... the assignment error is eliminated, but the read is not.
test.d(11): Error: incompatible types for ((StaticRegister) ==
(1)):
cannot use '==' with types
I argue that either both errors should be eliminated, or neither
should be eliminated. One could also argue that some variation
of the following should be required...
* static alias value this;
* alias static value this;
* alias value static this;
... to distinguish it from non-static `this`
Now, in the example below, `this` is referring to the type itself
in a static context
C)-------------------------------------------
import std.stdio;
struct StaticRegister {
static string GetType() { return typeof(this).stringof; }
}
void main(string[] s) {
writeln(StaticRegister.GetType());
}
-------------------------------------------
So, it follows that the example below should work... and it does
D)-------------------------------------------
struct StaticRegister {
static private uint _value = 0;
@property static uint value() { return _value; }
@property static void value(uint v) { _value= v; }
static uint GetValue() {
return this.value;
}
}
void main(string[] s) {
assert(StaticRegister.GetValue() == 0);
}
-------------------------------------------
So, why does `alias this` in a static context (See example B
above) only half-work? Bug? If not, what's the design rationale?
Thanks,
Mike
