On Tuesday, 20 June 2017 06:52:58 UTC+2, Will Hawkins wrote:
>
> I know that there is a difference between interface values and dynamic
> types and dynamic values. Is it possible that the documentation about the
> %T is misleading? Should it be more specific that it returns the variable's
> "dynamic type."
> [...]
>
Should the documentation for %T be updated to say that it prints the
> variable's dynamic type?
>
Well, no.
Look at fmt.Printf: It take a format string and a bunch of interface{}
values to
be printed. If %T would print the static type it always would print
interface{}.
To be useful Printf has too look inside it's arguments and inside is a
HelloInt.
The HelloListen basically gets lost while repacking the actual HelloInt
into the
empty interface{} of Printf's arguments.
So all is fine, all is consistent and no documentation is misleading.
It is just that fmt.Printf is not a magical function working outside of the
type
system. Any argument you supply is assigned to an empty interface. This
is how argument passing in Go works. You might try:
var empty interface{}
empty = hellolisten
fmt.Printf("empty: %T\n", empty)
which makes this repacking into an interface{} explicit and now it is
obvious
that it will print main.HelloInt.
V.
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