fix: panic when Decode's input is array and output is a slice

mapstructure.go

@@ -1088,7 +1088,7 @@ func (d *Decoder) decodeSlice(name string, data interface{}, val reflect.Value)
 	}
 
 	// If the input value is nil, then don't allocate since empty != nil
-	if dataVal.IsNil() {
+	if dataValKind != reflect.Array && dataVal.IsNil() {
 		return nil
 	}
 

mapstructure_test.go

@@ -556,6 +556,38 @@ func TestDecode_EmbeddedArray(t *testing.T) {
 	}
 }
 
+func TestDecode_decodeSliceWithArray(t *testing.T) {
+	t.Parallel()
+
+	data := []struct {
+		title  string
+		input  interface{}
+		result interface{}
+		exp    interface{}
+	}{
+		{
+			title:  "input is array and result is slice",
+			input:  [1]int{1},
+			result: []int{},
+			exp:    []int{1},
+		},
+	}
+
+	for _, d := range data {
+		d := d
+		t.Run(d.title, func(t *testing.T) {
+			t.Parallel()
+			if err := Decode(d.input, &d.result); err != nil {
+				t.Fatalf("got an err: %s", err.Error())
+			}
+
+			if !reflect.DeepEqual(d.exp, d.result) {
+				t.Errorf("wanted %+v, got %+v", d.exp, d.result)
+			}
+		})
+	}
+}
+
 func TestDecode_EmbeddedNoSquash(t *testing.T) {
 	t.Parallel()