feature/dynamodb/attributevalue: Fix string alias unmarshal (#1388)

Fixes unmarshaler's decoding of AttributeValueMemberN into a type that is a string alias.

.changelog/1d09c67fd2aa4bb1adfbe42f8218f7a2.json

@@ -0,0 +1,8 @@
+{
+    "id": "1d09c67f-d2aa-4bb1-adfb-e42f8218f7a2",
+    "type": "bugfix",
+    "description": "Fix unmarshaler's decoding of AttributeValueMemberN into a type that is a string alias.",
+    "modules": [
+        "feature/dynamodb/attributevalue"
+    ]
+}

feature/dynamodb/attributevalue/decode.go

@@ -327,7 +327,7 @@ func (d *Decoder) decodeNumber(n string, v reflect.Value, fieldTag tag) error {
 			v.SetString(n)
 			return nil
 		}
-		v.Set(reflect.ValueOf(n))
+		v.SetString(n)
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
 		i, err := strconv.ParseInt(n, 10, 64)
 		if err != nil {

feature/dynamodb/attributevalue/decode_test.go

@@ -723,3 +723,45 @@ func TestDecoderFieldByIndex(t *testing.T) {
 		t.Error("expected f to be an int with value equal to outer.Inner")
 	}
 }
+func TestDecodeAliasType(t *testing.T) {
+	type Str string
+	type Int int
+	type Uint uint
+	type TT struct {
+		A Str
+		B Int
+		C Uint
+		S Str
+	}
+
+	expect := TT{
+		A: "12345",
+		B: 12345,
+		C: 12345,
+		S: "string",
+	}
+	m := map[string]types.AttributeValue{
+		"A": &types.AttributeValueMemberN{
+			Value: "12345",
+		},
+		"B": &types.AttributeValueMemberN{
+			Value: "12345",
+		},
+		"C": &types.AttributeValueMemberN{
+			Value: "12345",
+		},
+		"S": &types.AttributeValueMemberS{
+			Value: "string",
+		},
+	}
+
+	var actual TT
+	err := UnmarshalMap(m, &actual)
+	if err != nil {
+		t.Fatalf("expect no error, got %v", err)
+	}
+
+	if !reflect.DeepEqual(expect, actual) {
+		t.Errorf("expect:\n%v\nactual:\n%v", expect, actual)
+	}
+}