gps: better information for panic on nil version

kevinburke · kevinburke · commit da0cc0dba509 · 2019-03-09T10:10:14.000-08:00
Patch originally suggested by Denis Subbotin (denis@subbot.in),
submitting under my name to pass Go CLA bot checks.
diff --git a/gps/solver.go b/gps/solver.go
@@ -912,7 +912,7 @@ func (s *solver) findValidVersion(q *versionQueue, pl []string) error {
 	if nil == q.current() {
 		// this case should not be reachable, but reflects improper solver state
 		// if it is, so panic immediately
-		panic("version queue is empty, should not happen")
+		panic("version queue is empty, should not happen: " + string(q.id.ProjectRoot) + " " + q.id.Source)
 	}
 
 	faillen := len(q.fails)

Original file line number	Diff line number	Diff line change
`@@ -912,7 +912,7 @@ func (s solver) findValidVersion(q versionQueue, pl []string) error {`
`912`	`912`	`if nil == q.current() {`
`913`	`913`	`// this case should not be reachable, but reflects improper solver state`
`914`	`914`	`// if it is, so panic immediately`
`915`		`- panic("version queue is empty, should not happen")`
	`915`	`+ panic("version queue is empty, should not happen: " + string(q.id.ProjectRoot) + " " + q.id.Source)`
`916`	`916`	`}`
`917`	`917`
`918`	`918`	`faillen := len(q.fails)`