On Monday, 8 April 2013 at 23:48:13 UTC, bearophile wrote:
On request by Maxim Fomin I ask an opinion here. This is a very
small enhancement request, that for me is borderline bug report
(so originally I didn't plan in showing it in the main D
newsgroup):
http://d.puremagic.com/issues/show_bug.cgi?id=9857
Maybe this should be valid:
struct Foo {
int opCall(bool b) {
return 0;
}
}
void main() {
Foo foo;
auto b1 = foo(true); // OK
auto b2 = true.foo; // Error
}
dmd 2.063alpha gives:
temp.d(9): Error: no property 'foo' for type 'bool'
Explanation:
1) I am using UFCS often in D, for functions, higher order
functions, etc. A struct with an opCall method is usable like a
function with state. So for uniformity with the other functions
I'd like to use it with UFCS. When you have a long UFCS chain
you don't want to break it, if it's possible.
2) Both struct constructors, struct implicit constructors and
struct static opCall support UFCS, so I don't see a good reason
for just the normal struct opCall to not support it:
struct Foo {
static int opCall(int x) {
return x * 2;
}
}
struct Bar {
int x;
this(int y) {
x = y * 2;
}
}
struct Spam {
int x;
}
void main() {
assert(10.Foo == 20);
assert(10.Bar.x == 20);
assert(10.Spam.x == 10);
}
I don't think this makes any sense. Constructor are not regular
function. The bug lies in the fact that this work and not in the
opCall not working IMO.
Regarding UFCS, currently this doesn't work, I don't know if
this should be considered a bug or not (I think the answer is
positive):
struct Node {}
void foo(Node* p) {}
void main() {
auto p = new Node();
foo(p); // OK
p.foo; // Error: no property 'foo' for type 'Node'
}
It is unspecified if the UFCS lookup happen before or after
pointer dereference, or both.
