Bug 9340 – Covariant return type conflicts with out contract.

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()); }

*** This issue has been marked as a duplicate of issue 10479 ***