internal/vulncheck: add Unalias call

Change-Id: I640f27e8418d5cb49c8af35b8679bde25eb30196
Reviewed-on: https://go-review.googlesource.com/c/vuln/+/645055
Auto-Submit: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Zvonimir Pavlinovic <zpavlinovic@google.com>
diff --git a/internal/vulncheck/utils.go b/internal/vulncheck/utils.go
index e752f4a..fb32a2c 100644
--- a/internal/vulncheck/utils.go
+++ b/internal/vulncheck/utils.go
@@ -93,7 +93,7 @@
 //   - pointer designation * is skipped
 //   - full path prefix is skipped as well
 func dbTypeFormat(t types.Type) string {
-	switch tt := t.(type) {
+	switch tt := types.Unalias(t).(type) {
 	case *types.Pointer:
 		return dbTypeFormat(tt.Elem())
 	case *types.Named: