fix: improve structparscan-struct

Use 'unsafe' to modify private struct fields, allowing to keep
unmodified field names: before they were prefixed with a capital.

Parse package statement. Provide a also a default package name for
REPL and tests. The support of packages is still incomplete.

2 files changed, 15 insertions, 4 deletions

diff --git a/vm/type.go b/vm/type.go
index 49215db..7c33cd2 100644
--- a/vm/type.go
+++ b/vm/type.go
@@ -6,12 +6,16 @@ import "reflect"
 
 // Type is the representation of a runtime type.
 type Type struct {
-	Name  string
-	Rtype reflect.Type
+	PkgPath string
+	Name    string
+	Rtype   reflect.Type
 }
 
 func (t *Type) String() string {
 	if t.Name != "" {
+		if t.PkgPath != "" {
+			return t.PkgPath + "." + t.Name
+		}
 		return t.Name
 	}
 	return t.Rtype.String()
@@ -84,7 +88,8 @@ func FuncOf(arg, ret []*Type, variadic bool) *Type {
 func StructOf(fields []*Type) *Type {
 	rf := make([]reflect.StructField, len(fields))
 	for i, f := range fields {
-		rf[i].Name = "X" + f.Name
+		rf[i].Name = f.Name
+		rf[i].PkgPath = f.PkgPath
 		rf[i].Type = f.Rtype
 	}
 	return &Type{Rtype: reflect.StructOf(rf)}
diff --git a/vm/vm.go b/vm/vm.go
index 408be6e..3cb9358 100644
--- a/vm/vm.go
+++ b/vm/vm.go
@@ -6,6 +6,7 @@ import (
 	"log"     // for tracing only
 	"reflect" // for optional CallX only
 	"strconv" // for tracing only
+	"unsafe"  // to allow setting unexported struct fields
 )
 
 const debug = true
@@ -184,7 +185,12 @@ func (m *Machine) Run() (err error) {
 		case Fdup:
 			mem = append(mem, mem[int(op[2])+fp-1])
 		case Field:
-			mem[sp-1].Data = mem[sp-1].Data.FieldByIndex(slint(op[2:]))
+			fv := mem[sp-1].Data.FieldByIndex(slint(op[2:]))
+			if !fv.CanSet() {
+				// Normally private fields can not bet set via reflect. Override this limitation.
+				fv = reflect.NewAt(fv.Type(), unsafe.Pointer(fv.UnsafeAddr())).Elem()
+			}
+			mem[sp-1].Data = fv
 		case Jump:
 			ip += int(op[2])
 			continue