The `infix` declaration was generating a delaborator, but it is
producing the invalid term
```
ConstantFunction.f myFun 3 <|> fun _ => ConstantFunction.f myFun 4
```
It is invalid because the `macro_rules` for `<|>` is based on
`binop_lazy%` which introduces the `fun _ =>` for us.
I tried to use
```
notation:20 a:21 " <|> " b:20 => HOrElse.hOrElse a fun _ : Unit => b
```
but the delaborator generator does not work for this case.
