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package restruct
import (
// typeMap maps identifiers to reflect.Types.
var typeMap = map[string]reflect.Type{
"bool": reflect.TypeOf(bool(false)),
"uint8": reflect.TypeOf(uint8(0)),
"uint16": reflect.TypeOf(uint16(0)),
"uint32": reflect.TypeOf(uint32(0)),
"uint64": reflect.TypeOf(uint64(0)),
"int8": reflect.TypeOf(int8(0)),
"int16": reflect.TypeOf(int16(0)),
"int32": reflect.TypeOf(int32(0)),
"int64": reflect.TypeOf(int64(0)),
"float32": reflect.TypeOf(float32(0)),
"float64": reflect.TypeOf(float64(0)),
"complex64": reflect.TypeOf(complex64(0)),
"complex128": reflect.TypeOf(complex128(0)),
"byte": reflect.TypeOf(uint8(0)),
"rune": reflect.TypeOf(int32(0)),
"uint": reflect.TypeOf(uint(0)),
"int": reflect.TypeOf(int(0)),
"uintptr": reflect.TypeOf(uintptr(0)),
"string": reflect.SliceOf(reflect.TypeOf(uint8(0))),
// typeOfExpr gets a type corresponding to an expression.
func typeOfExpr(expr ast.Expr) (reflect.Type, error) {
switch expr := expr.(type) {
return nil, fmt.Errorf("unexpected expression: %T", expr)
case *ast.ArrayType:
switch expr.Len {
case ast.Expr(nil):
// Slice
sub, err := typeOfExpr(expr.Elt)
if err != nil {
return nil, err
return reflect.SliceOf(sub), nil
// Parse length expression
lexpr, ok := expr.Len.(*ast.BasicLit)
if !ok {
return nil, fmt.Errorf("invalid array size expression")
if lexpr.Kind != token.INT {
return nil, fmt.Errorf("invalid array size type")
len, err := strconv.Atoi(lexpr.Value)
if err != nil {
return nil, err
// Parse elem type expression
sub, err := typeOfExpr(expr.Elt)
if err != nil {
return nil, err
return arrayOf(len, sub), nil
case *ast.Ident:
// Primitive types
typ, ok := typeMap[expr.Name]
if !ok {
return nil, fmt.Errorf("unknown type %s", expr.Name)
return typ, nil
case *ast.StarExpr:
// Pointer
sub, err := typeOfExpr(expr.X)
if err != nil {
return nil, err
return reflect.PtrTo(sub), nil
case *ast.ChanType:
return nil, fmt.Errorf("channel type not allowed")
case *ast.MapType:
return nil, fmt.Errorf("map type not allowed")
// parseType parses a Golang type string and returns a reflect.Type.
func parseType(typ string) (reflect.Type, error) {
expr, err := parser.ParseExpr(typ)
if err != nil {
return nil, errors.Wrap(err, "parsing error")
return typeOfExpr(expr)