http://d.puremagic.com/issues/show_bug.cgi?id=9340
Summary: Covariant return type conflicts with out contract.
Product: D
Version: D2
Platform: All
OS/Version: All
Status: NEW
Severity: major
Priority: P2
Component: DMD
AssignedTo: [email protected]
ReportedBy: [email protected]
--- Comment #0 from Adrian Matoga <[email protected]> 2013-01-17 14:55:58 PST ---
The following test case fails to compile with the following error message:
test.d(21): Error: cast(const(BaseBar))__result is not an lvalue
Comment out line (1) or change ConcreteBar to BaseBar in (2) and it compiles.
That means the workaround is to use base type in the overriding method.
import std.stdio;
class BaseBar
{
abstract string bar();
}
class BaseFoo
{
abstract BaseBar createBar()
out(result) { assert(result !is null); } body { assert(false); } // (1)
}
class ConcreteBar : BaseBar
{
override string bar() { return "ConcreteBar"; }
}
class ConcreteFoo : BaseFoo
{
override ConcreteBar createBar() { return new ConcreteBar(); } // (2)
}
void main()
{
auto foo = new ConcreteFoo();
writeln(foo.createBar().bar());
}
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