unused: we may still encounter interesting objects from export data

unused/unused.go

@@ -529,6 +529,8 @@ func (c *Checker) Result() []types.Object {
 			continue
 		}
 		position := c.fset.PositionFor(v.Pos(), false)
+		position.Column = 1
+		position.Offset = 0
 		if _, ok := c.seen[position]; !ok {
 			out2 = append(out2, v)
 		}
@@ -669,13 +671,27 @@ func (c *Checker) results() []types.Object {
 	report := func(node *Node) {
 		if node.seen {
 			var pos token.Pos
-			switch obj := node.obj.(type) {
-			case types.Object:
+			if obj, ok := node.obj.(types.Object); ok {
 				pos = obj.Pos()
 			}
 
-			if pos != 0 {
+			if pos != token.NoPos {
 				position := c.fset.PositionFor(pos, false)
+				// All packages passed on the command line are being
+				// loaded from source. However, thanks to tests and
+				// test variants of packages, we encounter the same
+				// object many different times. Worse, some of these
+				// forms may have been loaded from export data
+				// (despite being a variant of a package we've loaded
+				// from source…). Objects from export data do not have
+				// column information, so we force it to one, so that
+				// objects loaded from source and from export have the
+				// same position.
+				//
+				// SImilarly, the "offset" differs, too.
+
+				position.Column = 1
+				position.Offset = 0
 				c.seenMu.Lock()
 				c.seen[position] = struct{}{}
 				c.seenMu.Unlock()