fix(aarch64): bug when unmarshal into prefilled interface slice (#751)

decode_test.go

@@ -2162,6 +2162,8 @@ func TestSkipArrayObjects(t *testing.T) {
 // slices, and arrays.
 // Issues 4900 and 8837, among others.
 func TestPrefilled(t *testing.T) {
+    var one int = 1
+    var two int = 2
     // Values here change, cannot reuse table across runs.
     var prefillTests = []struct {
         in  string
@@ -2183,6 +2185,11 @@ func TestPrefilled(t *testing.T) {
             ptr: &[]int{1},
             out: &[]int{2},
         },
+        {
+            in:  `[2]`,
+            ptr: &[]int{1, 3},
+            out: &[]int{2},
+        },
         {
             in:  `[2, 3]`,
             ptr: &[]int{1},
@@ -2198,6 +2205,17 @@ func TestPrefilled(t *testing.T) {
             ptr: &[...]int{1, 2},
             out: &[...]int{3, 0},
         },
+        {
+            in:  `[2]`,
+            ptr: &[]interface{}{&one, 2.0},
+            out: &[]interface{}{&two},
+        },
+        // TODO(rfc): different with encoding/json
+        // {
+        //     in:  `{"a": 2}`,
+        //     ptr: &map[string]interface{}{"a": &one, "b": int(2)},
+        //     out: &map[string]interface{}{"a": 2.0, "b": int(2)},
+        // },
     }
 
     for _, tt := range prefillTests {

internal/decoder/optdec/slice.go

@@ -95,7 +95,18 @@ func (d *sliceEfaceDecoder) FromDom(vp unsafe.Pointer, node Node, ctx *context)
 		return nil
 	}
 
-	return node.AsSliceEface(ctx, vp)
+	/* if slice is empty, just call `AsSliceEface` */
+	if ((*rt.GoSlice)(vp)).Len == 0 {
+		return node.AsSliceEface(ctx, vp)
+	}
+
+	decoder := sliceDecoder{
+		elemType: rt.AnyType,
+		elemDec:  &efaceDecoder{},
+		typ:      rt.SliceEfaceType.Pack(),
+	}
+
+	return decoder.FromDom(vp, node, ctx)
 }
 
 type sliceI32Decoder struct {

issue_test/common_test.go

@@ -0,0 +1,31 @@
+// Copyright 2025 CloudWeGo Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package issue_test
+
+import (
+	"testing"
+
+	"encoding/json"
+	"github.com/bytedance/sonic"
+	"github.com/stretchr/testify/assert"
+)
+
+func assertUnmarshal(t *testing.T, api sonic.API, input []byte, newfn func() interface{}) {
+	sv, jv := newfn(), newfn()
+	serr := api.Unmarshal(input, sv)
+	jerr := json.Unmarshal(input, jv)
+	assert.Equal(t, jv, sv)
+	assert.Equal(t, serr == nil, jerr == nil)
+}

issue_test/issue750_test.go

@@ -0,0 +1,31 @@
+// Copyright 2025 CloudWeGo Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package issue_test
+
+import (
+	"testing"
+
+	"github.com/bytedance/sonic"
+)
+
+func genSlice() interface{} {
+	a := []string{}
+	return &[]interface{}{&a}
+}
+
+func TestSlicePointer_Issue750(t *testing.T) {
+	assertUnmarshal(t, sonic.ConfigStd, []byte(`[["one","2"]]`), genSlice)
+
+}