From 2ca842682b33e0b255cd1fed5b302945d2e30294 Mon Sep 17 00:00:00 2001
From: Tamara Vedenina <ts.vedenina@gmail.com>
Date: Sun, 28 Feb 2021 17:56:44 +0300
Subject: [PATCH] extend nilValReturn checker

---
 checkers/nilValReturn_checker.go              | 21 ++++++++++++-------
 .../testdata/nilValReturn/negative_tests.go   | 21 +++++++++++++++++++
 .../testdata/nilValReturn/positive_tests.go   | 16 ++++++++++++++
 3 files changed, 51 insertions(+), 7 deletions(-)

diff --git a/checkers/nilValReturn_checker.go b/checkers/nilValReturn_checker.go
index e53ca0cc0..0a8e793ee 100644
--- a/checkers/nilValReturn_checker.go
+++ b/checkers/nilValReturn_checker.go
@@ -45,17 +45,24 @@ func (c *nilValReturnChecker) VisitStmt(stmt ast.Stmt) {
 		return
 	}
 	ret, ok := ifStmt.Body.List[0].(*ast.ReturnStmt)
-	if !ok || len(ret.Results) != 1 {
+	if !ok {
 		return
 	}
 	expr, ok := ifStmt.Cond.(*ast.BinaryExpr)
-	cond := ok &&
-		expr.Op == token.EQL &&
+	if !ok {
+		return
+	}
+	xIsNil := expr.Op == token.EQL &&
 		typep.SideEffectFree(c.ctx.TypesInfo, expr.X) &&
-		qualifiedName(expr.Y) == "nil" &&
-		astequal.Expr(expr.X, ret.Results[0])
-	if cond {
-		c.warn(ret, expr.X)
+		qualifiedName(expr.Y) == "nil"
+	if !xIsNil {
+		return
+	}
+	for _, res := range ret.Results {
+		if astequal.Expr(expr.X, res) {
+			c.warn(ret, expr.X)
+			break
+		}
 	}
 }
 
diff --git a/checkers/testdata/nilValReturn/negative_tests.go b/checkers/testdata/nilValReturn/negative_tests.go
index 22de5653c..df4757037 100644
--- a/checkers/testdata/nilValReturn/negative_tests.go
+++ b/checkers/testdata/nilValReturn/negative_tests.go
@@ -22,6 +22,13 @@ func explicitNil() {
 		return nil
 	}
 
+	_ = func(o *object, err error) (*object, error) {
+		if err == nil {
+			return o, nil
+		}
+		return nil, err
+	}
+
 	_ = func(pointers [][][]map[string]*int) *int {
 		if pointers[0][1][2]["ptr"] == nil {
 			return nil
@@ -55,6 +62,20 @@ func explicitNotEqual() {
 		return nil
 	}
 
+	_ = func(o *object, a *object) *object {
+		if o != nil {
+			return o
+		}
+		return a
+	}
+
+	_ = func(o *object, err error) (*object, error) {
+		if err != nil {
+			return nil, err
+		}
+		return o, nil
+	}
+
 	_ = func(pointers [][][]map[string]*int) *int {
 		if pointers[0][1][2]["ptr"] != nil {
 			return pointers[0][1][2]["ptr"]
diff --git a/checkers/testdata/nilValReturn/positive_tests.go b/checkers/testdata/nilValReturn/positive_tests.go
index 454c1d4db..68037af66 100644
--- a/checkers/testdata/nilValReturn/positive_tests.go
+++ b/checkers/testdata/nilValReturn/positive_tests.go
@@ -29,6 +29,22 @@ func suspiciousReturns() {
 		return nil
 	}
 
+	_ = func(o *object, err error) (*object, error) {
+		if err == nil {
+			/*! returned expr is always nil; replace err with nil */
+			return nil, err
+		}
+		return o, nil
+	}
+
+	_ = func(o *object, a *object) *object {
+		if o == nil {
+			/*! returned expr is always nil; replace o with nil */
+			return o
+		}
+		return a
+	}
+
 	_ = func(pointers [][][]map[string]*int) *int {
 		if pointers[0][1][2]["ptr"] == nil {
 			/*! returned expr is always nil; replace pointers[0][1][2]["ptr"] with nil */