fix(util/gconv): fix incompatable converting to nil pointer target from older version implement (#4224)

fixed: #4218

Author: gqcn

util/gconv/gconv_z_unit_issue_test.go

@@ -806,6 +806,41 @@ func Test_Issue3903(t *testing.T) {
 	})
 }
 
+// https://github.com/gogf/gf/issues/4218
+func Test_Issue4218(t *testing.T) {
+	gtest.C(t, func(t *gtest.T) {
+		type SysMenuVo struct {
+			MenuId   int64        `json:"menuId"     orm:"menu_id"`
+			MenuName string       `json:"menuName"   orm:"menu_name"`
+			Children []*SysMenuVo `json:"children"   orm:"children"`
+			ParentId int64        `json:"parentId"   orm:"parent_id"`
+		}
+		menus := []*SysMenuVo{
+			{
+				MenuId:   1,
+				MenuName: "系统管理",
+				ParentId: 0,
+			},
+			{
+				MenuId:   2,
+				MenuName: "字典查询",
+				ParentId: 1,
+			},
+		}
+		var parent *SysMenuVo
+		err := gconv.Scan(menus[0], &parent)
+		t.AssertNil(err)
+		t.Assert(parent.MenuId, 1)
+		t.Assert(parent.ParentId, 0)
+
+		parent.Children = append(parent.Children, menus[1])
+
+		t.Assert(len(menus[0].Children), 1)
+		t.Assert(menus[0].Children[0].MenuId, 2)
+		t.Assert(menus[0].Children[0].ParentId, 1)
+	})
+}
+
 // https://github.com/gogf/gf/issues/4542
 func Test_Issue4542(t *testing.T) {
 	// Test case 1: Nested map conversion - map[string]any to map[string]map[string]float64

util/gconv/internal/converter/converter_scan.go

@@ -96,11 +96,14 @@ func (c *Converter) Scan(srcValue any, dstPointer any, option ...ScanOption) (er
 	}
 
 	// Get the element type and kind of dstPointer
-	var (
-		dstPointerReflectValueElem     = dstPointerReflectValue.Elem()
-		dstPointerReflectValueElemKind = dstPointerReflectValueElem.Kind()
-	)
+	var dstPointerReflectValueElem = dstPointerReflectValue.Elem()
+	// Check if srcValue and dstPointer are the same type, in which case direct assignment can be performed
+	if ok := c.doConvertWithTypeCheck(srcValueReflectValue, dstPointerReflectValueElem); ok {
+		return nil
+	}
+
 	// Handle multiple level pointers
+	var dstPointerReflectValueElemKind = dstPointerReflectValueElem.Kind()
 	if dstPointerReflectValueElemKind == reflect.Pointer {
 		if dstPointerReflectValueElem.IsNil() {
 			// Create a new value for the pointer dereference
@@ -114,11 +117,6 @@ func (c *Converter) Scan(srcValue any, dstPointer any, option ...ScanOption) (er
 		return c.Scan(srcValueReflectValue, dstPointerReflectValueElem, option...)
 	}
 
-	// Check if srcValue and dstPointer are the same type, in which case direct assignment can be performed
-	if ok := c.doConvertWithTypeCheck(srcValueReflectValue, dstPointerReflectValueElem); ok {
-		return nil
-	}
-
 	scanOption := c.getScanOption(option...)
 	// Handle different destination types
 	switch dstPointerReflectValueElemKind {