NewThing[int, int]() returns a map[int]int, and therefore that's the type
of MySet in func runInt.
You can think of NewThing[T1, T2] as a family of functions, like
func NewThing_int_int() map[int]int { ... }
func NewThing_int_byteslice() map[int][]byte { ... }
... etc
On Wednesday, 15 December 2021 at 17:01:41 UTC seank...@gmail.com wrote:
> when writing type parameterized code, it has to work with anything that
> could be passed to it.
> but once instantiated, the type is known and it can be used with its
> concrete type
>
> like `map` can be thought of as declared to be `map[comparable]any`
> but when you use it, the type is always known, eg. `map[string]int`
> On Wednesday, December 15, 2021 at 5:39:39 PM UTC+1 Johannes Kohnen wrote:
>
>> Hello folks,
>>
>> I've stumbled over a thing and I don't understand if what I've found is
>> intentionally possible by design...
>>
>> https://go.dev/play/p/SIxOV1FnTzX?v=gotip
>>
>> Why can I compare int with == when it was instantiated from the "any"
>> type parameter?
>>
>> The origin of my question is my implementation of a left right map which
>> I've ported to generics. While doing so I've uncovered a couple bugs in
>> Jetbrains GoLand and reported them. Except this one, because I've
>> overlooked it and I now am confused:
>>
>>
>> https://github.com/jwkohnen/lrmap/blob/a6b9a6715069a7ad24de7cf84fe949dd7f194c0a/lrmap_test.go#L26
>>
>> In this line I compare two int values with !=, and this code compiles.
>> Though, those value types were instantiated from the "any" type
>> constraint. GoLand reports an error in that line "Invalid operation: _v !=
>> v (the operator != is not defined on V)".
>>
>> From my reading of the generics proposal GoLand is right, but the
>> compiler says otherwise. How exactly are the operations that are defined
>> on an "any" type inferred?
>>
>> Sorry if the answer is right there in the proposal; my reading
>> comprehension fluctuates wildly these days.
>>
>> Cheers,
>> Johannes
>>
>
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