On 03/29/2013 12:33 PM, "Artur Zawłocki" <[email protected]>" wrote:
On Thursday, 28 March 2013 at 18:24:19 UTC, Timon Gehr wrote:
(...)
Indeed, the above code should not compile. My upcoming D front end
currently reports the following after fixing the grammatical mistakes
(For now. The error message text should maybe be improved. Ideas
welcome.)
tt.d:2:32: error: declaration of 'x' smells suspiciously fishy
static if (!is(typeof(y))) int x = 1;
^
tt.d:1:23: note: this lookup should have succeeded if it was valid
static if (!is(typeof(x))) int y = 1;
^
tt.d:1:32: error: declaration of 'y' smells suspiciously fishy
static if (!is(typeof(x))) int y = 1;
^
tt.d:2:23: note: this lookup should have succeeded if it was valid
static if (!is(typeof(y))) int x = 1;
^
Surely it will be fun to work with (though 'this lookup' message is
somewhat confusing)!
Yes. What would be a better message?
There are lots of similar analysis order issues without static if.
(Luckily, they can be detected well enough conservatively in a quite
general way.) The following is a simplified example from my test suite:
class A{ int string; }
template Mixin(string s){
mixin("alias "~s~" Mixin;");
}
class D: Mixin!({D d = new D; return d.foo();}()){
int foo(int x){ return 2;}
string foo(){ return "A"; }
}
The problem is of course that 'string' has to be resolved in order to
compute the parent of 'D'. However, that parent then changes the
meaning of 'string' in the subclass scope. Therefore, the code is
meaningless.
I am lost here. Are 'int string' in A
Yes.
in and 'int foo(int)' in D
No.
relevant?
Shouldn't this example fail simply because in order to process
the declaration of D the compiler needs to instantiate D in the delegate
body?
No, D's parent is not required to be known in order to execute what is
in the delegate body.
So this would be similar to:
template Mixin(bool b : true) {
alias Object Mixin;
}
class D: Mixin!(new D == new D) {}
This fails because new D == new D is false. (Otherwise it would work.)
