On Friday, 1 September 2017 at 23:25:04 UTC, Jesse Phillips wrote:
I've love being able to inherit and override generic functions
in C#. Unfortunately C# doesn't use templates and I hit so many
other issues where Generics just suck.
I don't think it is appropriate to dismiss the need for the
compiler to generate a virtual function for every instantiated
T, after all, the compiler can't know you have a finite known
set of T unless you tell it.
But lets assume we've told the compiler that it is compiling
all the source code and it does not need to compile for future
linking.
First the compiler will need to make sure all virtual functions
can be generated for the derived classes. In this case the
compiler must note the template function and validate all
derived classes include it. That was easy.
Next up each instantiation of the function needs a new v-table
entry in all derived classes. Current compiler implementation
will compile each module independently of each other; so this
feature could be specified to work within the same module or
new semantics can be written up of how the compiler modifies
already compiled modules and those which reference the compiled
modules (the object sizes would be changing due to the v-table
modifications)
With those three simple changes to the language I think that
this feature will work for every T.
Specifying that there will be no further linkage is the same as
making T finite. T must be finite.
C# uses generics/IR/CLR so it can do things at run time that is
effectively compile time for D.
By simply extending the grammar slightly in an intuitive way, we
can get the explicit finite case, which is easy:
foo(T in [A,B,C])()
and possibly for your case
foo(T in <module>)() would work
or
foo(T in <program>)()
the `in` keyword makes sense here and is not used nor ambiguous,
I believe.
Regardless of the implementation, the idea that we should throw
the baby out with the bathwater is simply wrong. At least there
are a few who get that. By looking in to it in a serious manner
an event better solution might be found. Not looking at all
results in no solutions and no progress.
