Arnaud,
$ go version && go run alias.go && go vet alias.go
go version devel go1.24-96d8ff00c2 Sat Aug 24 00:51:40 2024 +0000
linux/amd64
b = {X:0xc00011c190 Y:0xc00011c1a0}
$
Or
$ go1.23 version && go1.23 run alias.go && GODEBUG=gotypesalias=1 go1.23
vet alias.go
go version go1.23.0 linux/amd64
b = {X:0xc0000141c0 Y:0xc0000141d0}
$
peter
On Saturday, August 24, 2024 at 5:37:20 PM UTC-4 Arnaud Delobelle wrote:
> Hi all
>
> I ran into this error with generic types. Here is the sample program
> below, which is my best effort to boil it down to its simplest expression.
>
> I can build and run the program fine with go 1.23.0. However, on line 15
> vscode reports the error I put in the comment on that line. I do not know
> how to determine what tool is instructing vscode to report this error (I
> imagine it's gopls but I have no proof).
>
> package main
>
> import "fmt"
>
> func main() {
> b := B{X: &A1{X: B{}}, Y: &A2{X: B{}}}
> fmt.Printf("b = %#v", b)
> }
>
> type A1 struct {
> X B
> }
>
> type A2 struct {
> X B // invalid use of type alias B in recursive type (see
> go.dev/issue/50729)compilerInvalidDeclCycle
> }
>
> type G[T1, T2 any] struct {
> X *T1
> Y *T2
> }
>
> type B = G[A1, A2]
>
>
> Here is the same program in the go playground:
> https://go.dev/play/p/fjy9259UHPY. If I click "Run" I get this output:
>
> # [play]
> vet: ./prog.go:15:4: invalid use of type alias B in recursive type (see
> go.dev/issue/50729)
> Go vet failed.
> b = {X:0xc00009e050 Y:0xc00009e060}
> Program exited.
>
>
> So "go vet" fails, but the program builds and runs OK. However, if I run
> "go vet" on my machine, no errors are reported!
>
> Can someone explain what is happening? To sum up
> - the program builds and runs even though an error is reported in vscode
> and the same error by go vet on the Go playground
> - go vet reports an error in the Go playground, but not on my machine
> (they both reportedly run go 1.23.0)
> - possibly gopls reports this error too? I do not know if it is the tool
> that tells vscode of the error on my machine (I run gopls 0.16.1)
>
> What I'd like to know:
> - if someone can tell me how to determine what tool is telling vscode to
> report this error, it would help me find where to report this issue
> - if someone could confirm whether the program is indeed supposed to be
> correct, it would also help me (I suspect it should be correct, as it
> builds and runs successfully)
>
> Thanks in advance
>
> --
> Arnaud
>
> PS: Apologies for the html-formatted email, but I couldn't figure out how
> to paste code into gmail without losing all the indentation
>
>
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