Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go1.9.3 darwin/amd64

What did you do?

Run the following program:

package main

func main() {
	fmt.Printf("%[1]d \n", 1, 2, 3)
	fmt.Printf("%d \n", 1, 2, 3)
}

It prints the first line without problems, and prints the second one with errors. As far I understand, when there are explicit arguments in the format string, fmt does not report errors about extra arguments (see: #22867).

Now, run go vet on this file.

What did you expect to see?

Error is reported only for the second line.

What did you see instead?

Errors are reported for both lines.