cmd/vet: not reporting bad index for the incorrect statement

[dlsniper]

1. What version of Go are you using (go version)?
   1.6.2
2. What operating system and processor architecture are you using (go env)?
   linux/amd64
3. What did you do?
   The following code:

myWrongFormatVar := "%d %d %#[1]x %#x %2.f %d %2.2f %.f %.3f %[9]*.[2]*[3]f %d %f %#[1]x %#x %[2]d %v % d"
log.Printf(myWrongFormatVar, 1, 2, 3, 4, 5, 6, 7, 8)

produces a BADINDEX at runtime however go vet doesn't catch it. To correct the code one should add a tenth argument to the Printf function and all should be ok.

In fact it should catch if the function has more than 9 other arguments (besides the formatting string) but it doesn't.

The other scenario is this:

log.Printf("%d %d %#[1]x %#x %f %2.f %2.2f %.f %.3f %[3]*.[2]*[1]f %d %d %#[1]x %#x %*[2]d %v % d", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)

https://play.golang.org/p/snrXok614V

1. What did you expect to see?
   An error about the BADINDEX
2. What did you see instead?
   No error.

[dlsniper]

Work on this is a bit more complicated as the initial patch only solves part of the problem, the indexing part still needs a bit more work.

[dlsniper]

I have updated the description with the other bad case scenario.

[quentinmit]

/cc @robpike @valyala based on recent commits

[valyala]

@dlsniper , @quentinmit , see the CL for this issue - https://go-review.googlesource.com/24391 .

[gopherbot]

CL https://golang.org/cl/24391 mentions this issue.