https://issues.dlang.org/show_bug.cgi?id=16415
Issue ID: 16415
Summary: Overload conflicts with mixin templates
Product: D
Version: D2
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P1
Component: dmd
Assignee: [email protected]
Reporter: [email protected]
I'm trying to implement the Visitor pattern and utilize template mixins to
avoid boilerplate by generating visit() methods for each type. DMD goes crazy
that the two visit() overloads conflict with each other, despite overloads
accepting different types (A and B in my case):
//-----------------------------------
interface Visitor(types...)
{
mixin generateMethods!types;
private mixin template generateMethods(types...)
{
static if (types.length)
{
mixin generateMethod!(types[0]); // but this works: void
visit(types[0]);
mixin generateMethods!(types[1..$]);
}
}
private mixin template generateMethod(T)
{
void visit(T);
}
}
alias TestVisitor = Visitor!(A, B);
mixin template AcceptVisitor()
{
void accept(TestVisitor v)
{
v.visit(this);
}
}
class A
{
mixin AcceptVisitor;
}
class B: A
{
override mixin AcceptVisitor;
}
//-----------------------------------
P.S. As a side note, can we please have "static foreach" everywhere, just like
"static if"? I just want this to work:
interface Visitor(types...)
{
static foreach (T; types)
void visit(T);
}
But D doesn't allow that, so I'm forced to use recursive mixin templates.
"Recursive" doesn't mean "elegant" all the time, in this case it's the
opposite. Should I make a DIP or it's not gonna happen? Why is this even
forbidden in the first place?
--
