Fix: false positive from deferred funcs (#24)

- this adds more liberal checking of deferred functions to look for
  any usage of End/RecordError/SetStatus.

spancheck.go

@@ -360,18 +360,19 @@ func usesCall(
 	startSpanMatchers []spanStartMatcher,
 	depth int,
 ) bool {
-	if depth > 1 { // for perf reasons, do not dive too deep thru func literals, just one level deep check.
+	if depth > 1 { // for perf reasons, do not dive too deep thru func literals, just two levels deep.
 		return false
 	}
 
+	cfgs := pass.ResultOf[ctrlflow.Analyzer].(*ctrlflow.CFGs)
+
 	found, reAssigned := false, false
 	for _, subStmt := range stmts {
 		stack := []ast.Node{}
 		ast.Inspect(subStmt, func(n ast.Node) bool {
 			switch n := n.(type) {
 			case *ast.FuncLit:
 				if len(stack) > 0 {
-					cfgs := pass.ResultOf[ctrlflow.Analyzer].(*ctrlflow.CFGs)
 					g := cfgs.FuncLit(n)
 					if g != nil && len(g.Blocks) > 0 {
 						return usesCall(pass, g.Blocks[0].Nodes, sv, selName, ignoreCheckSig, startSpanMatchers, depth+1)
@@ -387,6 +388,32 @@ func usesCall(
 						return false
 					}
 				}
+			case *ast.DeferStmt:
+				if n.Call == nil {
+					break
+				}
+
+				f, ok := n.Call.Fun.(*ast.FuncLit)
+				if !ok {
+					break
+				}
+
+				if g := cfgs.FuncLit(f); g != nil && len(g.Blocks) > 0 {
+					for _, b := range g.Blocks {
+						if usesCall(
+							pass,
+							b.Nodes,
+							sv,
+							selName,
+							ignoreCheckSig,
+							startSpanMatchers,
+							depth+1,
+						) {
+							found = true
+							return false
+						}
+					}
+				}
 			case nil:
 				if len(stack) > 0 {
 					stack = stack[:len(stack)-1] // pop

testdata/disableerrorchecks/disable_error_checks.go

@@ -56,3 +56,15 @@ func _() error {
 }
 
 func recordErr(span trace.Span, err error) {}
+
+// https://github.com/jjti/go-spancheck/issues/24
+func _() (err error) {
+	_, span := otel.Tracer("foo").Start(context.Background(), "bar")
+	defer func() {
+		recordErr(span, err)
+
+		span.End()
+	}()
+
+	return errors.New("test")
+}

testdata/enableall/enable_all.go

@@ -249,3 +249,41 @@ func _() error {
 
 // 	return errors.New("test")
 // }
+
+// https://github.com/jjti/go-spancheck/issues/24
+func _() (err error) {
+	_, span := otel.Tracer("foo").Start(context.Background(), "bar")
+	defer func() {
+		if err != nil {
+			span.RecordError(err)
+			span.SetStatus(codes.Error, "test")
+		}
+
+		span.End()
+	}()
+
+	return errors.New("test")
+}
+
+func _() (err error) {
+	_, span := otel.Tracer("foo").Start(context.Background(), "bar") // want "span.SetStatus is not called on all paths"
+	defer func() {
+		if true {
+			span.End()
+		}
+		span.RecordError(err)
+	}()
+
+	return errors.New("test") // want "return can be reached without calling span.SetStatus"
+}
+
+func _() (err error) {
+	_, span := otel.Tracer("foo").Start(context.Background(), "bar")
+	defer func() {
+		span.RecordError(err)
+		span.SetStatus(codes.Error, "test")
+		span.End()
+	}()
+
+	return errors.New("test")
+}