Re:.NET NanoFramework
by DaiPlusPlus on Saturday January 16, 2021 @01:12PM
(#25804036)
Are “monomorphism” and “reification” interchangeable terms though? Considering how .NET now has covariant/contravariant generics I wonder if it could be described as having “polymorphic” generics as opposed to monomorphic generics - (unrelated to OOP polymorphism, ofc).
[ Parent
| on HN ]
Re:.NET NanoFramework
by sideeffffect on Saturday January 16, 2021 @01:49PM
(#25804346)
AFAIUI _monomorphisation_ and reification are interchangable.
That means, that if I have a polymorphic (generic) class `MyClassA<T>`, the compiler (regardless if it is JIT in the runtime as in C#, or AOT as in Rust) monomorphises (reifies) `MyClassA` for each instantiation of `T`. So `MyClassA<MyClassB>` and `MyClassA<MyClassC>` are distinct classes.
For this reason, co-/contra-variance in C# works only for interfaces. Type parameters in classes are invariant. `MyClassA<MyClassB>` and `MyClassA<MyClassC>` are distinct classes, neither sub-/super-class of the other, even if `MyClassB` were a subclass of `MyClassC`.