cmd/compile: fix recorded export data position info
The position information recorded now consists of the line-
directive relative filename and line number. It would be
relatively easy to also encode absolute position information
as necessary (by serializing src.PosBase data).
For example, given $GOROOT/src/tmp/x.go:
package p
const C0 = 0
//line c.go:10
const C1 = 1
//line t.go:20
type T int
//line v.go:30
var V T
//line f.go:40
func F() {}
The recorded positions for the exported entities are:
C0 $GOROOT/src/tmp/x.go 3
C1 c.go 10
T t.go 20
V v.go 30
F f.go 40
Fix verified by manual inspection. There's currently no easy way
to test this, but it will eventually be tested when we fix #7311.
Fixes #19391.
Change-Id: I6269067ea58358250fe6dd1f73bdf9e5d2adfe3d
Reviewed-on: https://go-review.googlesource.com/37936 Reviewed-by: Matthew Dempsky <mdempsky@google.com>