sorry again. It should be "the type set and specific types of interface{
int; any } are both {int}."
On Thursday, January 6, 2022 at 9:45:35 PM UTC+8 tapi...@gmail.com wrote:
> On Thursday, January 6, 2022 at 9:44:05 PM UTC+8 tapi...@gmail.com wrote:
>
>> On Thursday, January 6, 2022 at 9:40:49 PM UTC+8 Brian Candler wrote:
>>
>>> So to be more specific, I think you're asking why this code works:
>>> https://gotipplay.golang.org/p/kuYzzx4EJY1
>>>
>>> Sorry, I made a mistake in interpreting the spec. It also says:
>>>
>>> "The type set of the empty interface is the set of all types."
>>>
>>> Therefore, the type set of the intersection { int; any } is int - and
>>> hence f[int] is allowed.
>>>
>>> But the set of specific types
>>> <https://tip.golang.org/ref/spec#Structure_of_interfaces> is empty:
>>>
>>> "An interface specification which contains type elements
>>> <https://tip.golang.org/ref/spec#Interface_types> defines a (possibly
>>> empty) set of *specific types*. Loosely speaking, these are the
>>> types T that appear in the interface definition in terms of the form T, ~T,
>>> or in unions of such terms."
>>>
>>> The type set and the set of specific types can be different. Examples
>>> are given where one is empty and the other is non-empty:
>>>
>>> interface{ int; m() } // *[specific type]* int (but type set is empty
>>> because int has no method m)
>>> interface{ int; any } // no specific types (intersection is empty) *[even
>>> though the type set is not empty]*
>>>
>>> *Items in [italics/brackets] are my additions*
>>>
>>
>> > The type set and the set of specific types can be different
>>
>> This is true.
>>
>> > interface{ int; any } // no specific types (intersection is empty) *[even
>> though the type set is not empty]*
>>
>> I don't think this is true. In my opinion, the method set of specific
>> types of interface{ int; any } are both {int}.
>>
>
> sorry a typo: it should be
>
> the method set and specific types of interface{ int; any } are both {int}.
>
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