diff --git a/internal/backends/compiler_wat/compile_func.go b/internal/backends/compiler_wat/compile_func.go
index f339fb3..74a4c47 100644
--- a/internal/backends/compiler_wat/compile_func.go
+++ b/internal/backends/compiler_wat/compile_func.go
@@ -876,16 +876,23 @@ func (g *functionGenerator) genMakeClosre_Anonymous(inst *ssa.MakeClosure) (inst
 		panic("ret_type != inst.Type()")
 	}
 
-	var st_free_data wir.ValueType
+	var st_free_data *wir.Struct
 	{
-		var fields []wir.Field
-		for _, freevar := range f.FreeVars {
-			feild := wir.NewField(freevar.Name(), g.tLib.compile(freevar.Type()))
-			fields = append(fields, feild)
-		}
 		fn_internal_name, _ := wir.GetFnMangleName(f)
 		st_name := fn_internal_name + ".$warpdata"
-		st_free_data = g.module.GenValueType_Struct(st_name, fields)
+
+		var found bool
+		st_free_data, found = g.module.GenValueType_Struct(st_name)
+		if found {
+			logger.Fatalf("Type: %s already registered.", st_name)
+		}
+
+		for _, freevar := range f.FreeVars {
+			vtype := g.tLib.compile(freevar.Type())
+			field := g.module.NewStructField(freevar.Name(), vtype)
+			st_free_data.AppendField(field)
+		}
+		st_free_data.Finish()
 	}
 
 	var warp_fn_index int
diff --git a/internal/backends/compiler_wat/compile_type.go b/internal/backends/compiler_wat/compile_type.go
index 024d800..e4bcfde 100644
--- a/internal/backends/compiler_wat/compile_type.go
+++ b/internal/backends/compiler_wat/compile_type.go
@@ -41,9 +41,6 @@ func (tLib *typeLib) compile(from types.Type) wir.ValueType {
 		return *v
 	}
 
-	//s := from.String()
-	//println(s)
-
 	var newType wir.ValueType
 	tLib.typeTable[from.String()] = &newType
 	uncommanFlag := false
@@ -119,20 +116,23 @@ func (tLib *typeLib) compile(from types.Type) wir.ValueType {
 	case *types.Named:
 		switch ut := t.Underlying().(type) {
 		case *types.Struct:
-			//Todo: 待解决类型嵌套包含的问题
-			var fs []wir.Field
-			for i := 0; i < ut.NumFields(); i++ {
-				f := ut.Field(i)
-				wtyp := tLib.compile(f.Type())
-				if f.Embedded() {
-					fs = append(fs, wir.NewField("$"+wtyp.Name(), wtyp))
-				} else {
-					fs = append(fs, wir.NewField(wir.GenSymbolName(f.Name()), wtyp))
-				}
-			}
 			pkg_name, _ := wir.GetPkgMangleName(t.Obj().Pkg().Path())
 			obj_name := wir.GenSymbolName(t.Obj().Name())
-			tStruct := tLib.module.GenValueType_Struct(pkg_name+"."+obj_name, fs)
+			tStruct, found := tLib.module.GenValueType_Struct(pkg_name + "." + obj_name)
+			if !found {
+				for i := 0; i < ut.NumFields(); i++ {
+					sf := ut.Field(i)
+					dtyp := tLib.compile(sf.Type())
+					if sf.Embedded() {
+						df := tLib.module.NewStructField("$"+dtyp.Name(), dtyp)
+						tStruct.AppendField(df)
+					} else {
+						df := tLib.module.NewStructField(wir.GenSymbolName(sf.Name()), dtyp)
+						tStruct.AppendField(df)
+					}
+				}
+				tStruct.Finish()
+			}
 
 			newType = tStruct
 			uncommanFlag = true
diff --git a/internal/backends/compiler_wat/wir/instruction_emitter.go b/internal/backends/compiler_wat/wir/instruction_emitter.go
index bb4f19f..3c093e4 100644
--- a/internal/backends/compiler_wat/wir/instruction_emitter.go
+++ b/internal/backends/compiler_wat/wir/instruction_emitter.go
@@ -227,7 +227,7 @@ func (m *Module) EmitGenField(x Value, field_name string) (insts []wat.Inst, ret
 
 func (m *Module) EmitGenFieldAddr(x Value, field_name string) (insts []wat.Inst, ret_type ValueType) {
 	insts = append(insts, x.EmitPush()...)
-	var field *Field
+	var field *StructField
 	switch addr := x.(type) {
 	case *aRef:
 		field = addr.Type().(*Ref).Base.(*Struct).findFieldByName(field_name)
diff --git a/internal/backends/compiler_wat/wir/value_array.go b/internal/backends/compiler_wat/wir/value_array.go
index 57497c2..b132bb2 100644
--- a/internal/backends/compiler_wat/wir/value_array.go
+++ b/internal/backends/compiler_wat/wir/value_array.go
@@ -26,11 +26,18 @@ func (m *Module) GenValueType_Array(base ValueType, capacity int) *Array {
 		return t.(*Array)
 	}
 
-	var members []Field
-	for i := 0; i < capacity; i++ {
-		members = append(members, NewField("m"+strconv.Itoa(i), base))
+	var found bool
+	arr_t.underlying, found = m.GenValueType_Struct(arr_t.Name() + ".underlying")
+	if found {
+		logger.Fatalf("Type: %s already registered.", arr_t.Name()+".underlying")
 	}
-	arr_t.underlying = m.GenValueType_Struct(arr_t.Name()+".underlying", members)
+
+	for i := 0; i < capacity; i++ {
+		field := m.NewStructField("m"+strconv.Itoa(i), base)
+		arr_t.underlying.AppendField(field)
+	}
+	arr_t.underlying.Finish()
+
 	m.addValueType(&arr_t)
 	return &arr_t
 }
diff --git a/internal/backends/compiler_wat/wir/value_closure.go b/internal/backends/compiler_wat/wir/value_closure.go
index 989190b..1efffa1 100644
--- a/internal/backends/compiler_wat/wir/value_closure.go
+++ b/internal/backends/compiler_wat/wir/value_closure.go
@@ -84,10 +84,15 @@ func (m *Module) GenValueType_Closure(sig FnSig) *Closure {
 	closure_t._fn_type.Name = "closure$" + strconv.Itoa(_closure_id)
 	_closure_id++
 	m.AddFnType(&closure_t._fn_type)
-	var fields []Field
-	fields = append(fields, NewField("fn_index", m.U32))
-	fields = append(fields, NewField("data", m.GenValueType_Ref(m.VOID)))
-	closure_t.underlying = m.GenValueType_Struct(closure_t.Name()+".underlying", fields)
+
+	var found bool
+	closure_t.underlying, found = m.GenValueType_Struct(closure_t.Name() + ".underlying")
+	if found {
+		logger.Fatalf("Type: %s already registered.", closure_t.Name()+".underlying")
+	}
+	closure_t.underlying.AppendField(m.NewStructField("fn_index", m.U32))
+	closure_t.underlying.AppendField(m.NewStructField("data", m.GenValueType_Ref(m.VOID)))
+	closure_t.underlying.Finish()
 
 	m.addValueType(&closure_t)
 	return &closure_t
diff --git a/internal/backends/compiler_wat/wir/value_interface.go b/internal/backends/compiler_wat/wir/value_interface.go
index 06e52cf..de1d011 100644
--- a/internal/backends/compiler_wat/wir/value_interface.go
+++ b/internal/backends/compiler_wat/wir/value_interface.go
@@ -6,6 +6,7 @@ import (
 	"strconv"
 
 	"wa-lang.org/wa/internal/backends/compiler_wat/wir/wat"
+	"wa-lang.org/wa/internal/logger"
 )
 
 /**************************************
@@ -26,20 +27,16 @@ func (m *Module) GenValueType_Interface(name string) *Interface {
 	var interface_t Interface
 	interface_t.name = name
 
-	//interface_t.methodTab = make([]FnType, len(methods))
-	//copy(interface_t.methodTab, methods)
-	//
-	//for i := 0; i < s.NumMethods(); i++ {
-	//	var method FnType
-	//	method.Name = s.Method(i).Name()
-	//	method.FnSig = m.GenFnSig(s.Method(i).Type().(*types.Signature))
-	//	interface_t.methods = append(interface_t.methods, method)
-	//}
+	var found bool
+	interface_t.underlying, found = m.GenValueType_Struct(interface_t.Name() + ".underlying")
+	if found {
+		logger.Fatalf("Type: %s already registered.", interface_t.Name()+".underlying")
+	}
+
+	interface_t.underlying.AppendField(m.NewStructField("data", m.GenValueType_Ref(m.GenValueType_Ref(m.VOID))))
+	interface_t.underlying.AppendField(m.NewStructField("itab", m.U32))
+	interface_t.underlying.Finish()
 
-	var fields []Field
-	fields = append(fields, NewField("data", m.GenValueType_Ref(m.GenValueType_Ref(m.VOID))))
-	fields = append(fields, NewField("itab", m.U32))
-	interface_t.underlying = m.GenValueType_Struct(interface_t.Name()+".underlying", fields)
 	m.addValueType(&interface_t)
 	return &interface_t
 }
diff --git a/internal/backends/compiler_wat/wir/value_ref.go b/internal/backends/compiler_wat/wir/value_ref.go
index 707ec8f..f223cc1 100644
--- a/internal/backends/compiler_wat/wir/value_ref.go
+++ b/internal/backends/compiler_wat/wir/value_ref.go
@@ -30,10 +30,17 @@ func (m *Module) GenValueType_Ref(base ValueType) *Ref {
 	ref_t._base_block = m.GenValueType_Block(base)
 	ref_t._void = m.VOID
 	base_ptr := m.GenValueType_Ptr(base)
-	var members []Field
-	members = append(members, NewField("block", ref_t._base_block))
-	members = append(members, NewField("data", base_ptr))
-	ref_t.underlying = m.GenValueType_Struct(ref_t.Name()+".underlying", members)
+
+	var found bool
+	ref_t.underlying, found = m.GenValueType_Struct(ref_t.Name() + ".underlying")
+	if found {
+		logger.Fatalf("Type: %s already registered.", ref_t.Name()+".underlying")
+	}
+
+	ref_t.underlying.AppendField(m.NewStructField("block", ref_t._base_block))
+	ref_t.underlying.AppendField(m.NewStructField("data", base_ptr))
+	ref_t.underlying.Finish()
+
 	m.addValueType(&ref_t)
 	return &ref_t
 }
diff --git a/internal/backends/compiler_wat/wir/value_slice.go b/internal/backends/compiler_wat/wir/value_slice.go
index 35486ec..e3fedb4 100644
--- a/internal/backends/compiler_wat/wir/value_slice.go
+++ b/internal/backends/compiler_wat/wir/value_slice.go
@@ -34,12 +34,18 @@ func (m *Module) GenValueType_Slice(base ValueType) *Slice {
 	slice_t._base_block = m.GenValueType_Block(base)
 	slice_t._base_ptr = m.GenValueType_Ptr(base)
 
-	var members []Field
-	members = append(members, NewField("block", slice_t._base_block))
-	members = append(members, NewField("data", slice_t._base_ptr))
-	members = append(members, NewField("len", slice_t._u32))
-	members = append(members, NewField("cap", slice_t._u32))
-	slice_t.underlying = m.GenValueType_Struct(slice_t.Name()+".underlying", members)
+	var found bool
+	slice_t.underlying, found = m.GenValueType_Struct(slice_t.Name() + ".underlying")
+	if found {
+		logger.Fatalf("Type: %s already registered.", slice_t.Name()+".underlying")
+	}
+
+	slice_t.underlying.AppendField(m.NewStructField("block", slice_t._base_block))
+	slice_t.underlying.AppendField(m.NewStructField("data", slice_t._base_ptr))
+	slice_t.underlying.AppendField(m.NewStructField("len", slice_t._u32))
+	slice_t.underlying.AppendField(m.NewStructField("cap", slice_t._u32))
+	slice_t.underlying.Finish()
+
 	m.addValueType(&slice_t)
 	return &slice_t
 }
diff --git a/internal/backends/compiler_wat/wir/value_string.go b/internal/backends/compiler_wat/wir/value_string.go
index 0a6eb59..ff690dd 100644
--- a/internal/backends/compiler_wat/wir/value_string.go
+++ b/internal/backends/compiler_wat/wir/value_string.go
@@ -6,6 +6,7 @@ import (
 	"strconv"
 
 	"wa-lang.org/wa/internal/backends/compiler_wat/wir/wat"
+	"wa-lang.org/wa/internal/logger"
 )
 
 /**************************************
@@ -34,11 +35,17 @@ func (m *Module) GenValueType_String() *String {
 	str_t._u8_block = m.GenValueType_Block(m.U8)
 	str_t._u8_ptr = m.GenValueType_Ptr(m.U8)
 
-	var members []Field
-	members = append(members, NewField("block", str_t._u8_block))
-	members = append(members, NewField("data", str_t._u8_ptr))
-	members = append(members, NewField("len", str_t._u32))
-	str_t.underlying = m.GenValueType_Struct(str_t.Name()+".underlying", members)
+	var found bool
+	str_t.underlying, found = m.GenValueType_Struct(str_t.Name() + ".underlying")
+	if found {
+		logger.Fatalf("Type: %s already registered.", str_t.Name()+".underlying")
+	}
+
+	str_t.underlying.AppendField(m.NewStructField("block", str_t._u8_block))
+	str_t.underlying.AppendField(m.NewStructField("data", str_t._u8_ptr))
+	str_t.underlying.AppendField(m.NewStructField("len", str_t._u32))
+	str_t.underlying.Finish()
+
 	m.addValueType(&str_t)
 	return &str_t
 
diff --git a/internal/backends/compiler_wat/wir/value_struct.go b/internal/backends/compiler_wat/wir/value_struct.go
index 62ab515..94e472b 100644
--- a/internal/backends/compiler_wat/wir/value_struct.go
+++ b/internal/backends/compiler_wat/wir/value_struct.go
@@ -8,30 +8,35 @@ import (
 )
 
 /**************************************
-Field:
+StructField:
 **************************************/
-type Field struct {
+type StructField struct {
 	name     string
 	typ      ValueType
 	_start   int
 	_typ_ptr *Ptr //type of *typ
 }
 
-func NewField(n string, t ValueType) Field { return Field{name: n, typ: t} }
-func (i *Field) Name() string              { return i.name }
-func (i *Field) Type() ValueType           { return i.typ }
-func (i *Field) Equal(u Field) bool        { return i.name == u.name && i.typ.Equal(u.typ) }
+func (m *Module) NewStructField(name string, typ ValueType) *StructField {
+	f := StructField{name: name, typ: typ}
+	f._typ_ptr = m.GenValueType_Ptr(typ)
+	return &f
+}
+
+func (i *StructField) Name() string              { return i.name }
+func (i *StructField) Type() ValueType           { return i.typ }
+func (i *StructField) Equal(u *StructField) bool { return i.name == u.name && i.typ.Equal(u.typ) }
 
 /**************************************
 Struct:
 **************************************/
 type Struct struct {
 	tCommon
-	name    string
-	Members []Field
-	_size   int
-	_align  int
-	_u32    ValueType
+	name   string
+	fields []*StructField
+	_size  int
+	_align int
+	_u32   ValueType
 }
 
 type iStruct interface {
@@ -46,10 +51,10 @@ func makeAlign(i, align int) int {
 	return (i + align - 1) / align * align
 }
 
-func (m *Module) GenValueType_Struct(name string, fields []Field) *Struct {
+func (m *Module) GenValueType_Struct(name string) (*Struct, bool) {
 	t, ok := m.findValueType(name)
 	if ok {
-		return t.(*Struct)
+		return t.(*Struct), true
 	}
 
 	var struct_type Struct
@@ -57,32 +62,38 @@ func (m *Module) GenValueType_Struct(name string, fields []Field) *Struct {
 	struct_type._u32 = m.U32
 	m.addValueType(&struct_type)
 
-	for _, f := range fields {
-		ma := f.Type().align()
-		f._start = makeAlign(struct_type._size, ma)
-		f._typ_ptr = m.GenValueType_Ptr(f.typ)
-		struct_type.Members = append(struct_type.Members, f)
-
-		struct_type._size = f._start + f.Type().Size()
-		if ma > struct_type._align {
-			struct_type._align = ma
-		}
-	}
-	struct_type._size = makeAlign(struct_type._size, struct_type._align)
-	return &struct_type
+	return &struct_type, false
 }
 
 func (t *Struct) Name() string { return t.name }
 func (t *Struct) Size() int    { return t._size }
 func (t *Struct) align() int   { return t._align }
 
+func (t *Struct) AppendField(f *StructField) {
+	t.fields = append(t.fields, f)
+}
+
+func (t *Struct) Finish() {
+	t._size = 0
+	for _, field := range t.fields {
+		fa := field.Type().align()
+		field._start = makeAlign(t._size, fa)
+
+		t._size = field._start + field.Type().Size()
+		if fa > t._align {
+			t._align = fa
+		}
+	}
+	t._size = makeAlign(t._size, t._align)
+}
+
 type fn_offset_pair struct {
 	fn     int
 	offset int
 }
 
 func (t *Struct) genRawFree() (ret []fn_offset_pair) {
-	for _, member := range t.Members {
+	for _, member := range t.fields {
 		member_type := member.Type()
 		if istruct, ok := member_type.(iStruct); ok {
 			rfs := istruct.genRawFree()
@@ -131,7 +142,7 @@ func (t *Struct) onFree() int {
 
 func (t *Struct) Raw() []wat.ValueType {
 	var r []wat.ValueType
-	for _, f := range t.Members {
+	for _, f := range t.fields {
 		r = append(r, f.Type().Raw()...)
 	}
 	return r
@@ -143,12 +154,12 @@ func (t *Struct) Equal(u ValueType) bool {
 		return false
 	}
 
-	if len(t.Members) != len(ut.Members) {
+	if len(t.fields) != len(ut.fields) {
 		return false
 	}
 
-	for i := range t.Members {
-		if !t.Members[i].Equal(ut.Members[i]) {
+	for i := range t.fields {
+		if !t.fields[i].Equal(ut.fields[i]) {
 			return false
 		}
 	}
@@ -157,17 +168,17 @@ func (t *Struct) Equal(u ValueType) bool {
 }
 
 func (t *Struct) EmitLoadFromAddr(addr Value, offset int) (insts []wat.Inst) {
-	for _, m := range t.Members {
+	for _, m := range t.fields {
 		ptr := newValue_Ptr(addr.Name(), addr.Kind(), m._typ_ptr)
 		insts = append(insts, m.Type().EmitLoadFromAddr(ptr, m._start+offset)...)
 	}
 	return
 }
 
-func (t *Struct) findFieldByName(field_name string) *Field {
-	for i := range t.Members {
-		if t.Members[i].Name() == field_name {
-			return &t.Members[i]
+func (t *Struct) findFieldByName(field_name string) *StructField {
+	for i := range t.fields {
+		if t.fields[i].Name() == field_name {
+			return t.fields[i]
 		}
 	}
 	return nil
@@ -191,7 +202,7 @@ func newValue_Struct(name string, kind ValueKind, typ *Struct) *aStruct {
 	return &v
 }
 
-func (v *aStruct) genSubValue(m Field) Value {
+func (v *aStruct) genSubValue(m *StructField) Value {
 	if v.Kind() != ValueKindConst {
 		return newValue(v.Name()+"."+m.Name(), v.Kind(), m.Type())
 	} else {
@@ -217,7 +228,7 @@ func (v *aStruct) setFieldConstValue(field string, sv Value) {
 func (v *aStruct) raw() []wat.Value {
 	var r []wat.Value
 	st := v.Type().(*Struct)
-	for _, m := range st.Members {
+	for _, m := range st.fields {
 		t := v.genSubValue(m)
 		r = append(r, t.raw()...)
 	}
@@ -227,7 +238,7 @@ func (v *aStruct) raw() []wat.Value {
 func (v *aStruct) EmitInit() []wat.Inst {
 	var insts []wat.Inst
 	st := v.Type().(*Struct)
-	for _, m := range st.Members {
+	for _, m := range st.fields {
 		t := v.genSubValue(m)
 		insts = append(insts, t.EmitInit()...)
 	}
@@ -237,7 +248,7 @@ func (v *aStruct) EmitInit() []wat.Inst {
 func (v *aStruct) EmitPush() []wat.Inst {
 	var insts []wat.Inst
 	st := v.Type().(*Struct)
-	for _, m := range st.Members {
+	for _, m := range st.fields {
 		t := v.genSubValue(m)
 		insts = append(insts, t.EmitPush()...)
 	}
@@ -247,8 +258,8 @@ func (v *aStruct) EmitPush() []wat.Inst {
 func (v *aStruct) EmitPop() []wat.Inst {
 	var insts []wat.Inst
 	st := v.Type().(*Struct)
-	for i := range st.Members {
-		m := st.Members[len(st.Members)-i-1]
+	for i := range st.fields {
+		m := st.fields[len(st.fields)-i-1]
 		t := v.genSubValue(m)
 		insts = append(insts, t.EmitPop()...)
 	}
@@ -258,8 +269,8 @@ func (v *aStruct) EmitPop() []wat.Inst {
 func (v *aStruct) EmitRelease() []wat.Inst {
 	var insts []wat.Inst
 	st := v.Type().(*Struct)
-	for i := range st.Members {
-		m := st.Members[len(st.Members)-i-1]
+	for i := range st.fields {
+		m := st.fields[len(st.fields)-i-1]
 		t := v.genSubValue(m)
 		insts = append(insts, t.EmitRelease()...)
 	}
@@ -268,7 +279,7 @@ func (v *aStruct) EmitRelease() []wat.Inst {
 
 func (v *aStruct) Extract(member_name string) Value {
 	st := v.Type().(*Struct)
-	for _, m := range st.Members {
+	for _, m := range st.fields {
 		if m.Name() == member_name {
 			return v.genSubValue(m)
 		}
@@ -278,7 +289,7 @@ func (v *aStruct) Extract(member_name string) Value {
 
 func (v *aStruct) emitStoreToAddr(addr Value, offset int) (insts []wat.Inst) {
 	st := v.Type().(*Struct)
-	for _, m := range st.Members {
+	for _, m := range st.fields {
 		t := v.genSubValue(m)
 		ptr := newValue_Ptr(addr.Name(), addr.Kind(), m._typ_ptr)
 		insts = append(insts, t.emitStoreToAddr(ptr, m._start+offset)...)
@@ -288,7 +299,7 @@ func (v *aStruct) emitStoreToAddr(addr Value, offset int) (insts []wat.Inst) {
 
 func (v *aStruct) emitStore(offset int) (insts []wat.Inst) {
 	st := v.Type().(*Struct)
-	for _, m := range st.Members {
+	for _, m := range st.fields {
 		t := v.genSubValue(m)
 		insts = append(insts, t.emitStore(m._start+offset)...)
 	}
@@ -301,7 +312,7 @@ func (v *aStruct) Bin() (b []byte) {
 	}
 
 	b = make([]byte, v.typ.Size())
-	for _, m := range v.typ.Members {
+	for _, m := range v.typ.fields {
 		d := b[m._start:]
 		copy(d, v.genSubValue(m).Bin())
 	}
diff --git a/internal/backends/compiler_wat/wir/value_tuple.go b/internal/backends/compiler_wat/wir/value_tuple.go
index 94cba20..c061fe4 100644
--- a/internal/backends/compiler_wat/wir/value_tuple.go
+++ b/internal/backends/compiler_wat/wir/value_tuple.go
@@ -6,6 +6,7 @@ import (
 	"strconv"
 
 	"wa-lang.org/wa/internal/backends/compiler_wat/wir/wat"
+	"wa-lang.org/wa/internal/logger"
 )
 
 /**************************************
@@ -24,12 +25,18 @@ func (m *Module) GenValueType_Tuple(fields []ValueType) *Tuple {
 		return t.(*Tuple)
 	}
 
-	var members []Field
-	for i, t := range fields {
-		fname := "m" + strconv.Itoa(i)
-		members = append(members, NewField(fname, t))
+	var found bool
+	tuple_t.underlying, found = m.GenValueType_Struct(tuple_t.Name() + ".underlying")
+	if found {
+		logger.Fatalf("Type: %s already registered.", tuple_t.Name()+".underlying")
 	}
-	tuple_t.underlying = m.GenValueType_Struct(tuple_t.Name()+".underlying", members)
+
+	for i, t := range fields {
+		name := "m" + strconv.Itoa(i)
+		tuple_t.underlying.AppendField(m.NewStructField(name, t))
+	}
+	tuple_t.underlying.Finish()
+
 	m.addValueType(&tuple_t)
 	return &tuple_t
 }
@@ -98,9 +105,9 @@ func (v *aTuple) emitStoreToAddr(addr Value, offset int) []wat.Inst {
 
 func (v *aTuple) Extract(id int) Value {
 	st := v.typ.underlying
-	if id >= len(st.Members) {
+	if id >= len(st.fields) {
 		panic("id >= len(st.Members)")
 	}
 
-	return v.aStruct.genSubValue(st.Members[id])
+	return v.aStruct.genSubValue(st.fields[id])
 }