unused: fix false-positive (golangci#2772)

Author: ldez

pkg/golinters/unused.go

@@ -35,8 +35,27 @@ func NewUnused(settings *config.StaticCheckSettings) *goanalysis.Linter {
 
 			sr := unused.Serialize(pass, res.(unused.Result), pass.Fset)
 
+			used := make(map[string]bool)
+			for _, obj := range sr.Used {
+				used[fmt.Sprintf("%s %d %s", obj.Position.Filename, obj.Position.Line, obj.Name)] = true
+			}
+
 			var issues []goanalysis.Issue
+			// Inspired by https://github.com/dominikh/go-tools/blob/d694aadcb1f50c2d8ac0a1dd06217ebb9f654764/lintcmd/lint.go#L177-L197
 			for _, object := range sr.Unused {
+				if object.Kind == "type param" {
+					continue
+				}
+
+				if object.InGenerated {
+					continue
+				}
+
+				key := fmt.Sprintf("%s %d %s", object.Position.Filename, object.Position.Line, object.Name)
+				if used[key] {
+					continue
+				}
+
 				issue := goanalysis.NewIssue(&result.Issue{
 					FromLinter: name,
 					Text:       fmt.Sprintf("%s %s is unused", object.Kind, object.Name),