False positive when scanning a file and incorrect line number for suggested preallocation

[kellen-miller]

Example setup to reproduce the issue.

foo.txt

some dummy text

/* some comment */
more dummy text

// some comment
even more dummy text

main.go

type FooLine struct {
	Parts     []string
	LineFound int
}

type Foo struct {
	Words     []string
	LineFound int
}

func main() {
	file, err := os.Open("foo.txt")
	if err != nil {
		panic(err)
	}
	defer file.Close()

	var (
		lines      = bufio.NewScanner(file)
		lineNumber int
		foos       []*Foo
	)
	for lines.Scan() {
		lineNumber++

		line := lines.Text()
		if line == "" || strings.HasPrefix(line, "//") || strings.HasPrefix(line, "/*") {
			continue
		}

		foos = append(foos, &Foo{
			Words:     strings.Split(line, " "),
			LineFound: lineNumber,
		})
	}

	if err := lines.Err(); err != nil {
		panic(err)
	}

	println(foos)
}

Running prealloc -forloops main.go outputs:
main.go:21 Consider preallocating foos

Two issues:

1. Because I'm using a scanner, foos can't be preallocated. It's not possible to know information about the number of lines or data lines in the file.
2. Minor issue: prealloc is identifying the problem on line 21, however, that is the opening declaration of the var block var (. foos is actually on line 24. Not sure if this is possible to remedy, and not a huge issue since prealloc names the slice to consider preallocating in the output.