Type hints on hover are incorrect when omitting the value while ranging over a slice

[m90]

Considering the following program:

package main

import (
	"fmt"
)

func main() {
	s := []string{"a", "b", "c"}
	for index, char := range s {
		fmt.Println(index, char)
	}
	for index := range s {
		fmt.Println(index)
	}
}

with the rather obvious output of

0 a
1 b
2 c
0
1
2

I found a bug in the type hints that will be displayed when hovering over an expression in the editor.

Using 0.6.65, running Go 1.9 I will see the correct hint (int) when hovering over index in the first loop of the example:

when hovering over the second index, I will incorrectly be told that this is a bool (when it is still an int):

[ramya-rao-a]

@zmb3 Thoughts? I see the same when using gogetdoc as well.

[zmb3]

Interesting. I will look into it!

[zmb3]

@ramya-rao-a can we confirm vs-code is invoking gogetdoc with the correct offset? I'm not able to reproduce at the command line:

~/src/github.com/zmb3/doctest
❯ cat main.go
package main

import (
	"fmt"
)

func main() {
	s := []string{"a", "b", "c"}
	for index, char := range s {
		fmt.Println(index, char)
	}
	for index := range s {
		fmt.Println(index)
	}
}

~/src/github.com/zmb3/doctest
❯ gogetdoc -pos "main.go:#84"
import "github.com/zmb3/doctest"

var index int

Undocumented.


~/src/github.com/zmb3/doctest
❯ gogetdoc -pos "main.go:#144"
import "github.com/zmb3/doctest"

var index int

Undocumented.

[m90]

@zmb3 I just looked into this and it seems that the bug stems from the fact that the extension is falling back to godef as it is set to go.docsTool: godoc. If I use gogetdoc it will show me the correct type, bot in the extension as well as on the command line (which is great).

@ramya-rao-a this probably means it is still an upstream bug, but in godef. What's the reason for godoc as a default?

[m90]

Yes, I can confirm that godef prints incorrect information in this case:

frederik@fr-xps:~/projects/go/src/github.com/m90/test$ cat main.go 
package main

import (
	"fmt"
)

func main() {
	s := []string{"a", "b", "c"}
	for index, char := range s {
		fmt.Println(index, char)
	}
	for index := range s {
		fmt.Println(index)
	}
}

frederik@fr-xps:~/projects/go/src/github.com/m90/test$ godef -o 144 -f main.go -t
main.go:12:6
index bool

[ramya-rao-a]

Sorry about that @zmb3, I was so sure I had changed the setting to use gogetdoc when testing :(

@m90 godef gives the location and signature of the definition. We pass this to godoc to get further doc info.

Please open an issue in the godef repo so that @rogpeppe can take a look there

#1025 is tracking the feature request to make gogetdoc the default option as there are quite a few cases where the godef+godoc combo doesnt give the right results

Closing this issue for now as using gogetdoc gives you the right results