Refactor merge where exprs

clause/where.go

@@ -40,9 +40,10 @@ func (where Where) Build(builder Builder) {
 // MergeClause merge where clauses
 func (where Where) MergeClause(clause *Clause) {
 	if w, ok := clause.Expression.(Where); ok {
-		copiedExpressions := make([]Expression, len(w.Exprs))
-		copy(copiedExpressions, w.Exprs)
-		where.Exprs = append(copiedExpressions, where.Exprs...)
+		exprs := make([]Expression, len(w.Exprs)+len(where.Exprs))
+		copy(exprs, w.Exprs)
+		copy(exprs[len(w.Exprs):], where.Exprs)
+		where.Exprs = exprs
 	}
 
 	clause.Expression = where

statement_test.go

@@ -34,4 +34,3 @@ func TestWhereCloneCorruption(t *testing.T) {
 		})
 	}
 }
-

tests/named_polymorphic_test.go

@@ -14,6 +14,7 @@ type Hamster struct {
 }
 
 func TestNamedPolymorphic(t *testing.T) {
+	DB.Migrator().DropTable(&Hamster{})
 	DB.AutoMigrate(&Hamster{})
 
 	hamster := Hamster{Name: "Mr. Hammond", PreferredToy: Toy{Name: "bike"}, OtherToy: Toy{Name: "treadmill"}}