On Fri, Feb 2, 2018 at 7:10 AM, <d...@veryhaha.com> wrote:
>
> Why not make it untyped?
>
> package main
>
> type T bool
>
> func f() T {return T(false)}
>
> func main() {
> switch {
> case f(): // invalid case f() in switch (mismatched types T and bool)
> }
> }
The current language spec says that omitting the switch expression is
equivalent to writing `true`. If you actually write `true`, then,
following the usual rules for untyped constant expressions, it will
receive the type `bool`, and you would get the same mismatched type
error. You will see a similar case if you write `switch 0` and try to
compare with a named version of `int`. So the compiler is following
the language spec as currently written.
We could change the language spec to say that omitting the switch
expression is not equivalent to writing `true`, but instead, as you
suggest, compares each case to an untyped `true` value. I think the
main argument against that is that it makes the spec slightly more
complicated while bringing very little benefit. You could write it up
as a language change proposal if you like.
Ian
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