```D
struct Matrix(S, size_t M, size_t N)
{
}
alias Vector(S, size_t N) = Matrix!(S, N, 1);
enum isVector(V) = is(V == Vector!(S, N), S, size_t N); // it
doesn't work
enum isVectorCorrect(V) = is(V == Matrix!(U, N, 1), U, size_t N);
// the "correct" way and how much I like to REPEAT myself!
void foo(U)(Vector!(U, 3) a)
{
}
void bar(U)(U a) if (isVector!U)
{
}
void main()
{
import std.stdio;
Vector!(float, 3) v;
foo(v); // Error: none of the overloads of template
`app.doSomething` are callable using argument types
`!()(Matrix!(float, 3LU, 1LU))
bar(v); // failed constraint isVector!U
}
```
I went back to some of my old code and couldn't stand what I had
ended up with - If I already have a well-defined `Vector`, why do
I have to write extra code to implement `isVector`, and use
`isVector` instead of simply declaring the param to be `Vector`?
But that's simply the current state: it looks like DIP1023 isn't
going anywhere, and I'm not a compiler expert.
Note that I had to repeat `Matrix!(S, N, 1)` to for both `Vector`
and `isVector`.
Is there a way around this?!
--
It can get worse.
```D
alias Vec2(S) = Vector!(S, 2);
alias Vec3(S) = Vector!(S, 3);
enum isVec3(V) = is(V == Matrix!(S, 2, 1), S);
enum isVec3(V) = is(V == Matrix!(S, 3, 1), S);
void foobar(U)(U v) if (isVec3!U);
```
It works, but it hurts my eyes.
