cmd/vet: handle constant string addition in printf formats

[gopherbot]

by johan.samyn:

What steps will reproduce the problem?
Run 'go tool vet -v' on a go source that contains a log.Fatalf() or fmt.Sprintf() (or
alike), for which the pattern string is either completely on the next line, or the
pattern string is split in multiple strings that are concatenated with '+'.

What is the expected output?
No complaint from 'go vet'.

What do you see instead?
<sourcefilename>.go:<line>:<col>: can't check non-literal format in
call to Fatalf

Which compiler are you using (5g, 6g, 8g, gccgo)?
8g I guess, cause on Win7 32bit

Which operating system are you using?
Windows 7 (32bit), but I see the same on Ubuntu 12.04 (32bit)

Which version are you using?  (run 'go version')
Go version 1.0.3

Please provide any additional information below.
I searched the Mercurial history for changes to the src/cmd/vet folder, but did not see
anything that indicated this was already solved for the next release.

[gopherbot]

Comment 1 by johan.samyn:

An example:
C:\DEV\go> cat go-issue-4599.go
package main
import (
    "log"
    "os"
)
func main() {
    fn := "testfile.txt"
    f, err := os.Open(fn)
    if err != nil {
        log.Fatalf("Error %s opening"+
            " file", err)
    }
    defer f.Close()
}
C:\DEV\go> go tool vet -v go-issue-4599.go
Checking file go-issue-4599.go
go-issue-4599.go:12:3: can't check non-literal format in call to Fatalf
C:\DEV\go> 
--
Johan

[minux]

Comment 2:

Labels changed: added priority-later, go1.1maybe, removed priority-triage, go1.1.

Status changed to Accepted.

[rsc]

Comment 3:

The multiline part is not relevant. It's that vet doesn't handle constant string
addition like in "x" + "y". This should be easy to fix.

Labels changed: added go1.1, removed go1.1maybe.

[rsc]

Comment 4:

This issue was closed by revision 87c3c1b.

Status changed to Fixed.