Fix VM memory allocation optimizations by reducing what we allocate on the heap

internal/object/str.go

@@ -10,59 +10,59 @@ type String struct {
 	Value string
 }
 
-func (s *String) Len() int {
+func (s String) Len() int {
 	return utf8.RuneCountInString(s.Value)
 }
 
-func (s *String) Bool() bool {
+func (s String) Bool() bool {
 	return s.Value != ""
 }
 
-func (s *String) Type() Type {
+func (s String) Type() Type {
 	return StringType
 }
 
-func (s *String) Inspect() string {
+func (s String) Inspect() string {
 	return fmt.Sprintf("%#v", s.Value)
 }
 
-func (s *String) Clone() Object {
-	return &String{Value: s.Value}
+func (s String) Clone() Object {
+	return String{Value: s.Value}
 }
 
-func (s *String) String() string {
+func (s String) String() string {
 	return s.Value
 }
 
-func (s *String) Add(other Object) (Object, error) {
+func (s String) Add(other Object) (Object, error) {
 	if !AssertTypes(other, StringType) {
 		return nil, NewBinaryOpError(s, other, "+")
 	}
-	return &String{s.Value + other.(*String).Value}, nil
+	return String{s.Value + other.(String).Value}, nil
 }
 
-func (s *String) Mul(other Object) (Object, error) {
+func (s String) Mul(other Object) (Object, error) {
 	if !AssertTypes(other, IntegerType) {
 		return nil, NewBinaryOpError(s, other, "*")
 	}
-	return &String{strings.Repeat(s.Value, int(other.(*Integer).Value))}, nil
+	return String{strings.Repeat(s.Value, int(other.(Integer).Value))}, nil
 }
 
-func (s *String) Get(index Object) (Object, error) {
+func (s String) Get(index Object) (Object, error) {
 	if !AssertTypes(index, IntegerType) {
 		return nil, fmt.Errorf("invalid type for string index, expected Integer got %s", index.Type())
 	}
 
-	i := int(index.(*Integer).Value)
+	i := int(index.(Integer).Value)
 	if i < 0 || i >= len(s.Value) {
-		return &String{}, nil
+		return String{}, nil
 	}
 
-	return &String{string(s.Value[i])}, nil
+	return String{string(s.Value[i])}, nil
 }
 
-func (s *String) Compare(other Object) int {
-	if obj, ok := other.(*String); ok {
+func (s String) Compare(other Object) int {
+	if obj, ok := other.(String); ok {
 		switch {
 		case s.Value < obj.Value:
 			return -1