diff --git a/include/xo/expression2/DApplyExpr.hpp b/include/xo/expression2/DApplyExpr.hpp
index 072567c1..b4119def 100644
--- a/include/xo/expression2/DApplyExpr.hpp
+++ b/include/xo/expression2/DApplyExpr.hpp
@@ -83,7 +83,7 @@ namespace xo {
             ///@{
 
             std::size_t shallow_size() const noexcept;
-            DApplyExpr * shallow_move(obj<AAllocator> mm) const noexcept;
+            DApplyExpr * shallow_move(obj<ACollector> gc) noexcept;
             std::size_t forward_children(obj<ACollector> gc) noexcept;
 
             ///@}
diff --git a/include/xo/expression2/DConstant.hpp b/include/xo/expression2/DConstant.hpp
index da557fc9..e78440ad 100644
--- a/include/xo/expression2/DConstant.hpp
+++ b/include/xo/expression2/DConstant.hpp
@@ -63,7 +63,7 @@ namespace xo {
             ///@{
 
             size_t shallow_size() const noexcept;
-            DConstant * shallow_move(obj<AAllocator> mm) const noexcept;
+            DConstant * shallow_move(obj<ACollector> gc) noexcept;
             size_t forward_children(obj<ACollector> gc) noexcept;
 
             ///@}
diff --git a/include/xo/expression2/DDefineExpr.hpp b/include/xo/expression2/DDefineExpr.hpp
index b2cd7ed6..1e20c530 100644
--- a/include/xo/expression2/DDefineExpr.hpp
+++ b/include/xo/expression2/DDefineExpr.hpp
@@ -73,7 +73,7 @@ namespace xo {
             ///@{
 
             std::size_t shallow_size() const noexcept;
-            DDefineExpr * shallow_move(obj<AAllocator> mm) noexcept;
+            DDefineExpr * shallow_move(obj<ACollector> gc) noexcept;
             std::size_t forward_children(obj<ACollector> gc) noexcept;
 
             ///@}
diff --git a/include/xo/expression2/DGlobalSymtab.hpp b/include/xo/expression2/DGlobalSymtab.hpp
index 9ce29a6e..c6fcdcf1 100644
--- a/include/xo/expression2/DGlobalSymtab.hpp
+++ b/include/xo/expression2/DGlobalSymtab.hpp
@@ -43,6 +43,9 @@ namespace xo {
             DGlobalSymtab(dp<repr_type> var_map, DArray * vars,
                           dp<repr_type> type_map, DArray * types);
 
+            /** move constructor (needed because dp<> deletes copy ctor) **/
+            DGlobalSymtab(DGlobalSymtab && other) = default;
+
             /** create instance.
              *  Use memory from @p fixed_mm for @ref map_.
              *  Use memory from @p mm for DGlobalSymtab instance.
@@ -111,7 +114,7 @@ namespace xo {
             ///@{
 
             std::size_t shallow_size() const noexcept;
-            DGlobalSymtab * shallow_move(obj<AAllocator> mm) const noexcept;
+            DGlobalSymtab * shallow_move(obj<ACollector> gc) noexcept;
             std::size_t forward_children(obj<ACollector> gc) noexcept;
 
             ///@}
diff --git a/include/xo/expression2/DIfElseExpr.hpp b/include/xo/expression2/DIfElseExpr.hpp
index 1f04ced0..8ffee429 100644
--- a/include/xo/expression2/DIfElseExpr.hpp
+++ b/include/xo/expression2/DIfElseExpr.hpp
@@ -99,7 +99,7 @@ namespace xo {
             ///@{
 
             std::size_t shallow_size() const noexcept;
-            DIfElseExpr * shallow_move(obj<AAllocator> mm) const noexcept;
+            DIfElseExpr * shallow_move(obj<ACollector> gc) noexcept;
             std::size_t forward_children(obj<ACollector> gc) noexcept;
 
             ///@}
diff --git a/include/xo/expression2/DLambdaExpr.hpp b/include/xo/expression2/DLambdaExpr.hpp
index 58495395..0d8d2391 100644
--- a/include/xo/expression2/DLambdaExpr.hpp
+++ b/include/xo/expression2/DLambdaExpr.hpp
@@ -85,7 +85,7 @@ namespace xo {
             ///@{
 
             std::size_t shallow_size() const noexcept;
-            DLambdaExpr * shallow_move(obj<AAllocator> mm) const noexcept;
+            DLambdaExpr * shallow_move(obj<ACollector> gc) noexcept;
             std::size_t forward_children(obj<ACollector> gc) noexcept;
 
             ///@}
diff --git a/include/xo/expression2/DLocalSymtab.hpp b/include/xo/expression2/DLocalSymtab.hpp
index dbaad170..b2843cb9 100644
--- a/include/xo/expression2/DLocalSymtab.hpp
+++ b/include/xo/expression2/DLocalSymtab.hpp
@@ -98,7 +98,7 @@ namespace xo {
             ///@{
 
             std::size_t shallow_size() const noexcept;
-            DLocalSymtab * shallow_move(obj<AAllocator> mm) noexcept;
+            DLocalSymtab * shallow_move(obj<ACollector> gc) noexcept;
             std::size_t forward_children(obj<ACollector> gc) noexcept;
 
             ///@}
diff --git a/include/xo/expression2/DSequenceExpr.hpp b/include/xo/expression2/DSequenceExpr.hpp
index c70f5e72..f876cfac 100644
--- a/include/xo/expression2/DSequenceExpr.hpp
+++ b/include/xo/expression2/DSequenceExpr.hpp
@@ -73,7 +73,7 @@ namespace xo {
             ///@{
 
             std::size_t shallow_size() const noexcept;
-            DSequenceExpr * shallow_move(obj<AAllocator> mm) const noexcept;
+            DSequenceExpr * shallow_move(obj<ACollector> gc) noexcept;
             std::size_t forward_children(obj<ACollector> gc) noexcept;
 
             ///@}
diff --git a/include/xo/expression2/DTypename.hpp b/include/xo/expression2/DTypename.hpp
index 667082ad..7bd30931 100644
--- a/include/xo/expression2/DTypename.hpp
+++ b/include/xo/expression2/DTypename.hpp
@@ -54,7 +54,7 @@ namespace xo {
             ///@{
 
             size_t shallow_size() const noexcept;
-            DTypename * shallow_move(obj<AAllocator> mm) noexcept;
+            DTypename * shallow_move(obj<ACollector> gc) noexcept;
             size_t forward_children(obj<ACollector> gc) noexcept;
 
             ///@}
diff --git a/include/xo/expression2/DVarRef.hpp b/include/xo/expression2/DVarRef.hpp
index 26305923..65abddb2 100644
--- a/include/xo/expression2/DVarRef.hpp
+++ b/include/xo/expression2/DVarRef.hpp
@@ -55,7 +55,7 @@ namespace xo {
             ///@{
 
             size_t shallow_size() const noexcept;
-            DVarRef * shallow_move(obj<AAllocator> mm) const noexcept;
+            DVarRef * shallow_move(obj<ACollector> gc) noexcept;
             size_t forward_children(obj<ACollector> gc) noexcept;
 
             ///@}
diff --git a/include/xo/expression2/DVariable.hpp b/include/xo/expression2/DVariable.hpp
index 1b4f31d2..12abae94 100644
--- a/include/xo/expression2/DVariable.hpp
+++ b/include/xo/expression2/DVariable.hpp
@@ -63,7 +63,7 @@ namespace xo {
             ///@{
 
             size_t shallow_size() const noexcept;
-            DVariable * shallow_move(obj<AAllocator> mm) const noexcept;
+            DVariable * shallow_move(obj<ACollector> gc) noexcept;
             size_t forward_children(obj<ACollector> gc) noexcept;
 
             ///@}
diff --git a/include/xo/expression2/define/IGCObject_DDefineExpr.hpp b/include/xo/expression2/define/IGCObject_DDefineExpr.hpp
index df303b98..b2c45805 100644
--- a/include/xo/expression2/define/IGCObject_DDefineExpr.hpp
+++ b/include/xo/expression2/define/IGCObject_DDefineExpr.hpp
@@ -55,7 +55,7 @@ namespace xo {
 
             // non-const methods
             /** move instance using allocator **/
-            static Opaque shallow_move(DDefineExpr & self, obj<AAllocator> mm) noexcept;
+            static Opaque shallow_move(DDefineExpr & self, obj<ACollector> gc) noexcept;
             /** during GC: forward immdiate children **/
             static size_type forward_children(DDefineExpr & self, obj<ACollector> gc) noexcept;
             ///@}
diff --git a/include/xo/expression2/detail/IGCObject_DApplyExpr.hpp b/include/xo/expression2/detail/IGCObject_DApplyExpr.hpp
index c0b0f35b..75eac694 100644
--- a/include/xo/expression2/detail/IGCObject_DApplyExpr.hpp
+++ b/include/xo/expression2/detail/IGCObject_DApplyExpr.hpp
@@ -55,7 +55,7 @@ namespace xo {
 
             // non-const methods
             /** move instance using allocator **/
-            static Opaque shallow_move(DApplyExpr & self, obj<AAllocator> mm) noexcept;
+            static Opaque shallow_move(DApplyExpr & self, obj<ACollector> gc) noexcept;
             /** during GC: forward immdiate children **/
             static size_type forward_children(DApplyExpr & self, obj<ACollector> gc) noexcept;
             ///@}
diff --git a/include/xo/expression2/detail/IGCObject_DConstant.hpp b/include/xo/expression2/detail/IGCObject_DConstant.hpp
index 35bfbaa2..9cb72026 100644
--- a/include/xo/expression2/detail/IGCObject_DConstant.hpp
+++ b/include/xo/expression2/detail/IGCObject_DConstant.hpp
@@ -55,7 +55,7 @@ namespace xo {
 
             // non-const methods
             /** move instance using allocator **/
-            static Opaque shallow_move(DConstant & self, obj<AAllocator> mm) noexcept;
+            static Opaque shallow_move(DConstant & self, obj<ACollector> gc) noexcept;
             /** during GC: forward immdiate children **/
             static size_type forward_children(DConstant & self, obj<ACollector> gc) noexcept;
             ///@}
diff --git a/include/xo/expression2/detail/IGCObject_DIfElseExpr.hpp b/include/xo/expression2/detail/IGCObject_DIfElseExpr.hpp
index 5f9cf68e..e7d6fcfd 100644
--- a/include/xo/expression2/detail/IGCObject_DIfElseExpr.hpp
+++ b/include/xo/expression2/detail/IGCObject_DIfElseExpr.hpp
@@ -55,7 +55,7 @@ namespace xo {
 
             // non-const methods
             /** move instance using allocator **/
-            static Opaque shallow_move(DIfElseExpr & self, obj<AAllocator> mm) noexcept;
+            static Opaque shallow_move(DIfElseExpr & self, obj<ACollector> gc) noexcept;
             /** during GC: forward immdiate children **/
             static size_type forward_children(DIfElseExpr & self, obj<ACollector> gc) noexcept;
             ///@}
diff --git a/include/xo/expression2/detail/IGCObject_DLambdaExpr.hpp b/include/xo/expression2/detail/IGCObject_DLambdaExpr.hpp
index f44d2ac8..6cf2cd6c 100644
--- a/include/xo/expression2/detail/IGCObject_DLambdaExpr.hpp
+++ b/include/xo/expression2/detail/IGCObject_DLambdaExpr.hpp
@@ -55,7 +55,7 @@ namespace xo {
 
             // non-const methods
             /** move instance using allocator **/
-            static Opaque shallow_move(DLambdaExpr & self, obj<AAllocator> mm) noexcept;
+            static Opaque shallow_move(DLambdaExpr & self, obj<ACollector> gc) noexcept;
             /** during GC: forward immdiate children **/
             static size_type forward_children(DLambdaExpr & self, obj<ACollector> gc) noexcept;
             ///@}
diff --git a/include/xo/expression2/detail/IGCObject_DSequenceExpr.hpp b/include/xo/expression2/detail/IGCObject_DSequenceExpr.hpp
index df29b94f..9a9b3f9d 100644
--- a/include/xo/expression2/detail/IGCObject_DSequenceExpr.hpp
+++ b/include/xo/expression2/detail/IGCObject_DSequenceExpr.hpp
@@ -55,7 +55,7 @@ namespace xo {
 
             // non-const methods
             /** move instance using allocator **/
-            static Opaque shallow_move(DSequenceExpr & self, obj<AAllocator> mm) noexcept;
+            static Opaque shallow_move(DSequenceExpr & self, obj<ACollector> gc) noexcept;
             /** during GC: forward immdiate children **/
             static size_type forward_children(DSequenceExpr & self, obj<ACollector> gc) noexcept;
             ///@}
diff --git a/include/xo/expression2/detail/IGCObject_DVarRef.hpp b/include/xo/expression2/detail/IGCObject_DVarRef.hpp
index d002c5c9..3ca237b6 100644
--- a/include/xo/expression2/detail/IGCObject_DVarRef.hpp
+++ b/include/xo/expression2/detail/IGCObject_DVarRef.hpp
@@ -55,7 +55,7 @@ namespace xo {
 
             // non-const methods
             /** move instance using allocator **/
-            static Opaque shallow_move(DVarRef & self, obj<AAllocator> mm) noexcept;
+            static Opaque shallow_move(DVarRef & self, obj<ACollector> gc) noexcept;
             /** during GC: forward immdiate children **/
             static size_type forward_children(DVarRef & self, obj<ACollector> gc) noexcept;
             ///@}
diff --git a/include/xo/expression2/symtab/IGCObject_DGlobalSymtab.hpp b/include/xo/expression2/symtab/IGCObject_DGlobalSymtab.hpp
index f2a64385..43436ac8 100644
--- a/include/xo/expression2/symtab/IGCObject_DGlobalSymtab.hpp
+++ b/include/xo/expression2/symtab/IGCObject_DGlobalSymtab.hpp
@@ -55,7 +55,7 @@ namespace xo {
 
             // non-const methods
             /** move instance using allocator **/
-            static Opaque shallow_move(DGlobalSymtab & self, obj<AAllocator> mm) noexcept;
+            static Opaque shallow_move(DGlobalSymtab & self, obj<ACollector> gc) noexcept;
             /** during GC: forward immdiate children **/
             static size_type forward_children(DGlobalSymtab & self, obj<ACollector> gc) noexcept;
             ///@}
diff --git a/include/xo/expression2/symtab/IGCObject_DLocalSymtab.hpp b/include/xo/expression2/symtab/IGCObject_DLocalSymtab.hpp
index a5c0cd04..c8b9cca1 100644
--- a/include/xo/expression2/symtab/IGCObject_DLocalSymtab.hpp
+++ b/include/xo/expression2/symtab/IGCObject_DLocalSymtab.hpp
@@ -55,7 +55,7 @@ namespace xo {
 
             // non-const methods
             /** move instance using allocator **/
-            static Opaque shallow_move(DLocalSymtab & self, obj<AAllocator> mm) noexcept;
+            static Opaque shallow_move(DLocalSymtab & self, obj<ACollector> gc) noexcept;
             /** during GC: forward immdiate children **/
             static size_type forward_children(DLocalSymtab & self, obj<ACollector> gc) noexcept;
             ///@}
diff --git a/include/xo/expression2/typename/IGCObject_DTypename.hpp b/include/xo/expression2/typename/IGCObject_DTypename.hpp
index 45781a2e..d002a847 100644
--- a/include/xo/expression2/typename/IGCObject_DTypename.hpp
+++ b/include/xo/expression2/typename/IGCObject_DTypename.hpp
@@ -53,7 +53,7 @@ namespace xo {
 
             // non-const methods
             /** move instance using allocator **/
-            static Opaque shallow_move(DTypename & self, obj<AAllocator> mm) noexcept;
+            static Opaque shallow_move(DTypename & self, obj<ACollector> gc) noexcept;
             /** during GC: forward immdiate children **/
             static size_type forward_children(DTypename & self, obj<ACollector> gc) noexcept;
             ///@}
diff --git a/include/xo/expression2/variable/IGCObject_DVariable.hpp b/include/xo/expression2/variable/IGCObject_DVariable.hpp
index 9621d0f3..5fd34c21 100644
--- a/include/xo/expression2/variable/IGCObject_DVariable.hpp
+++ b/include/xo/expression2/variable/IGCObject_DVariable.hpp
@@ -55,7 +55,7 @@ namespace xo {
 
             // non-const methods
             /** move instance using allocator **/
-            static Opaque shallow_move(DVariable & self, obj<AAllocator> mm) noexcept;
+            static Opaque shallow_move(DVariable & self, obj<ACollector> gc) noexcept;
             /** during GC: forward immdiate children **/
             static size_type forward_children(DVariable & self, obj<ACollector> gc) noexcept;
             ///@}
diff --git a/src/expression2/DApplyExpr.cpp b/src/expression2/DApplyExpr.cpp
index 80f25139..9683d459 100644
--- a/src/expression2/DApplyExpr.cpp
+++ b/src/expression2/DApplyExpr.cpp
@@ -110,8 +110,11 @@ namespace xo {
         }
 
         DApplyExpr *
-        DApplyExpr::shallow_move(obj<AAllocator> mm) const noexcept {
-            DApplyExpr * copy = (DApplyExpr *)mm.alloc_copy((std::byte *)this);
+        DApplyExpr::shallow_move(obj<ACollector> gc) noexcept {
+            // note: not using ACollector.std_copy_for() here,
+            //       flexible array -> not move-constructible
+
+            DApplyExpr * copy = (DApplyExpr *)gc.alloc_copy_for(this);
 
             if (copy) {
                 copy->typeref_ = typeref_;
diff --git a/src/expression2/DConstant.cpp b/src/expression2/DConstant.cpp
index ea7a3d9f..420431bc 100644
--- a/src/expression2/DConstant.cpp
+++ b/src/expression2/DConstant.cpp
@@ -78,14 +78,9 @@ namespace xo {
         }
 
         DConstant *
-        DConstant::shallow_move(obj<AAllocator> mm) const noexcept
+        DConstant::shallow_move(obj<ACollector> gc) noexcept
         {
-            DConstant * copy = (DConstant *)mm.alloc_copy((std::byte *)this);
-
-            if (copy)
-                *copy = *this;
-
-            return copy;
+            return gc.std_copy_for(this);
         }
 
         std::size_t
diff --git a/src/expression2/DDefineExpr.cpp b/src/expression2/DDefineExpr.cpp
index 014da87c..e324b528 100644
--- a/src/expression2/DDefineExpr.cpp
+++ b/src/expression2/DDefineExpr.cpp
@@ -85,9 +85,9 @@ namespace xo {
         }
 
         DDefineExpr *
-        DDefineExpr::shallow_move(obj<AAllocator> mm) noexcept
+        DDefineExpr::shallow_move(obj<ACollector> gc) noexcept
         {
-            return mm.std_copy_for(this);
+            return gc.std_copy_for(this);
         }
 
         std::size_t
diff --git a/src/expression2/DGlobalSymtab.cpp b/src/expression2/DGlobalSymtab.cpp
index 2ea5b2ec..8d0f74cf 100644
--- a/src/expression2/DGlobalSymtab.cpp
+++ b/src/expression2/DGlobalSymtab.cpp
@@ -261,25 +261,9 @@ namespace xo {
         }
 
         DGlobalSymtab *
-        DGlobalSymtab::shallow_move(obj<AAllocator> mm) const noexcept
+        DGlobalSymtab::shallow_move(obj<ACollector> gc) noexcept
         {
-            /** can't use std_copy_for because of non-copyable dp<repr_type>
-             *
-             * TODO: rename to shallow_move() throughout, and have std_copy_for()
-             *       -> std_move_for()
-             *
-             **/
-
-            void * copy_mem = mm.alloc_copy_for(this);
-
-            if (copy_mem) {
-                DGlobalSymtab * self = const_cast<DGlobalSymtab*>(this);
-
-                return new (copy_mem) DGlobalSymtab(std::move(self->var_map_), vars_,
-                                                    std::move(self->type_map_), types_);
-            }
-
-            return nullptr;
+            return gc.std_copy_for(this);
         }
 
         std::size_t
diff --git a/src/expression2/DIfElseExpr.cpp b/src/expression2/DIfElseExpr.cpp
index 42d09fbb..3fb71682 100644
--- a/src/expression2/DIfElseExpr.cpp
+++ b/src/expression2/DIfElseExpr.cpp
@@ -89,14 +89,9 @@ namespace xo {
         }
 
         DIfElseExpr *
-        DIfElseExpr::shallow_move(obj<AAllocator> mm) const noexcept
+        DIfElseExpr::shallow_move(obj<ACollector> gc) noexcept
         {
-            DIfElseExpr * copy = (DIfElseExpr *)mm.alloc_copy((std::byte *)this);
-
-            if (copy)
-                *copy = *this;
-
-            return copy;
+            return gc.std_copy_for(this);
         }
 
         std::size_t
diff --git a/src/expression2/DLambdaExpr.cpp b/src/expression2/DLambdaExpr.cpp
index ebec0d40..4919840b 100644
--- a/src/expression2/DLambdaExpr.cpp
+++ b/src/expression2/DLambdaExpr.cpp
@@ -140,14 +140,8 @@ namespace xo {
         }
 
         DLambdaExpr *
-        DLambdaExpr::shallow_move(obj<AAllocator> mm) const noexcept {
-            DLambdaExpr * copy = (DLambdaExpr *)mm.alloc_copy((std::byte *)this);
-
-            if (copy) {
-                *copy = *this;
-            }
-
-            return copy;
+        DLambdaExpr::shallow_move(obj<ACollector> gc) noexcept {
+            return gc.std_copy_for(this);
         }
 
         std::size_t
diff --git a/src/expression2/DLocalSymtab.cpp b/src/expression2/DLocalSymtab.cpp
index cf021038..d1c4930c 100644
--- a/src/expression2/DLocalSymtab.cpp
+++ b/src/expression2/DLocalSymtab.cpp
@@ -119,9 +119,9 @@ namespace xo {
         }
 
         DLocalSymtab *
-        DLocalSymtab::shallow_move(obj<AAllocator> mm) noexcept
+        DLocalSymtab::shallow_move(obj<ACollector> gc) noexcept
         {
-            return mm.std_copy_for(this);
+            return gc.std_copy_for(this);
         }
 
         std::size_t
diff --git a/src/expression2/DSequenceExpr.cpp b/src/expression2/DSequenceExpr.cpp
index 39dcc999..33149785 100644
--- a/src/expression2/DSequenceExpr.cpp
+++ b/src/expression2/DSequenceExpr.cpp
@@ -120,14 +120,9 @@ namespace xo {
         }
 
         DSequenceExpr *
-        DSequenceExpr::shallow_move(obj<AAllocator> mm) const noexcept
+        DSequenceExpr::shallow_move(obj<ACollector> gc) noexcept
         {
-            DSequenceExpr * copy = (DSequenceExpr *)mm.alloc_copy((std::byte *)this);
-
-            if (copy)
-                *copy = *this;
-
-            return copy;
+            return gc.std_copy_for(this);
         }
 
         std::size_t
diff --git a/src/expression2/DTypename.cpp b/src/expression2/DTypename.cpp
index e02b483e..81509949 100644
--- a/src/expression2/DTypename.cpp
+++ b/src/expression2/DTypename.cpp
@@ -47,9 +47,9 @@ namespace xo {
         }
 
         DTypename *
-        DTypename::shallow_move(obj<AAllocator> mm) noexcept
+        DTypename::shallow_move(obj<ACollector> gc) noexcept
         {
-            return mm.std_copy_for(this);
+            return gc.std_copy_for(this);
         }
 
         size_t
diff --git a/src/expression2/DVarRef.cpp b/src/expression2/DVarRef.cpp
index e2866c23..186fa29a 100644
--- a/src/expression2/DVarRef.cpp
+++ b/src/expression2/DVarRef.cpp
@@ -65,14 +65,9 @@ namespace xo {
         }
 
         DVarRef *
-        DVarRef::shallow_move(obj<AAllocator> mm) const noexcept
+        DVarRef::shallow_move(obj<ACollector> gc) noexcept
         {
-            DVarRef * copy = (DVarRef *)mm.alloc_copy((std::byte *)this);
-
-            if (copy)
-                *copy = *this;
-
-            return copy;
+            return gc.std_copy_for(this);
         }
 
         std::size_t
diff --git a/src/expression2/DVariable.cpp b/src/expression2/DVariable.cpp
index 1b986c0b..f11000aa 100644
--- a/src/expression2/DVariable.cpp
+++ b/src/expression2/DVariable.cpp
@@ -45,15 +45,9 @@ namespace xo {
         }
 
         DVariable *
-        DVariable::shallow_move(obj<AAllocator> mm) const noexcept
+        DVariable::shallow_move(obj<ACollector> gc) noexcept
         {
-            DVariable * copy = (DVariable *)mm.alloc_copy((std::byte *)this);
-
-            if (copy) {
-                *copy = *this;
-            }
-
-            return copy;
+            return gc.std_copy_for(this);
         }
 
         size_t
diff --git a/src/expression2/IGCObject_DApplyExpr.cpp b/src/expression2/IGCObject_DApplyExpr.cpp
index 28375cce..2a731c0b 100644
--- a/src/expression2/IGCObject_DApplyExpr.cpp
+++ b/src/expression2/IGCObject_DApplyExpr.cpp
@@ -22,9 +22,9 @@ namespace xo {
         }
 
         auto
-        IGCObject_DApplyExpr::shallow_move(DApplyExpr & self, obj<AAllocator> mm) noexcept -> Opaque
+        IGCObject_DApplyExpr::shallow_move(DApplyExpr & self, obj<ACollector> gc) noexcept -> Opaque
         {
-            return self.shallow_move(mm);
+            return self.shallow_move(gc);
         }
         auto
         IGCObject_DApplyExpr::forward_children(DApplyExpr & self, obj<ACollector> gc) noexcept -> size_type
diff --git a/src/expression2/IGCObject_DConstant.cpp b/src/expression2/IGCObject_DConstant.cpp
index dff013b1..ae5a701f 100644
--- a/src/expression2/IGCObject_DConstant.cpp
+++ b/src/expression2/IGCObject_DConstant.cpp
@@ -22,9 +22,9 @@ namespace xo {
         }
 
         auto
-        IGCObject_DConstant::shallow_move(DConstant & self, obj<AAllocator> mm) noexcept -> Opaque
+        IGCObject_DConstant::shallow_move(DConstant & self, obj<ACollector> gc) noexcept -> Opaque
         {
-            return self.shallow_move(mm);
+            return self.shallow_move(gc);
         }
         auto
         IGCObject_DConstant::forward_children(DConstant & self, obj<ACollector> gc) noexcept -> size_type
diff --git a/src/expression2/IGCObject_DDefineExpr.cpp b/src/expression2/IGCObject_DDefineExpr.cpp
index 5adf8fc6..1e2c3bb8 100644
--- a/src/expression2/IGCObject_DDefineExpr.cpp
+++ b/src/expression2/IGCObject_DDefineExpr.cpp
@@ -22,9 +22,9 @@ namespace xo {
         }
 
         auto
-        IGCObject_DDefineExpr::shallow_move(DDefineExpr & self, obj<AAllocator> mm) noexcept -> Opaque
+        IGCObject_DDefineExpr::shallow_move(DDefineExpr & self, obj<ACollector> gc) noexcept -> Opaque
         {
-            return self.shallow_move(mm);
+            return self.shallow_move(gc);
         }
         auto
         IGCObject_DDefineExpr::forward_children(DDefineExpr & self, obj<ACollector> gc) noexcept -> size_type
diff --git a/src/expression2/IGCObject_DGlobalSymtab.cpp b/src/expression2/IGCObject_DGlobalSymtab.cpp
index 005e3ad3..3f596d01 100644
--- a/src/expression2/IGCObject_DGlobalSymtab.cpp
+++ b/src/expression2/IGCObject_DGlobalSymtab.cpp
@@ -22,9 +22,9 @@ namespace xo {
         }
 
         auto
-        IGCObject_DGlobalSymtab::shallow_move(DGlobalSymtab & self, obj<AAllocator> mm) noexcept -> Opaque
+        IGCObject_DGlobalSymtab::shallow_move(DGlobalSymtab & self, obj<ACollector> gc) noexcept -> Opaque
         {
-            return self.shallow_move(mm);
+            return self.shallow_move(gc);
         }
         auto
         IGCObject_DGlobalSymtab::forward_children(DGlobalSymtab & self, obj<ACollector> gc) noexcept -> size_type
diff --git a/src/expression2/IGCObject_DIfElseExpr.cpp b/src/expression2/IGCObject_DIfElseExpr.cpp
index 9c28f2e0..240906f2 100644
--- a/src/expression2/IGCObject_DIfElseExpr.cpp
+++ b/src/expression2/IGCObject_DIfElseExpr.cpp
@@ -22,9 +22,9 @@ namespace xo {
         }
 
         auto
-        IGCObject_DIfElseExpr::shallow_move(DIfElseExpr & self, obj<AAllocator> mm) noexcept -> Opaque
+        IGCObject_DIfElseExpr::shallow_move(DIfElseExpr & self, obj<ACollector> gc) noexcept -> Opaque
         {
-            return self.shallow_move(mm);
+            return self.shallow_move(gc);
         }
         auto
         IGCObject_DIfElseExpr::forward_children(DIfElseExpr & self, obj<ACollector> gc) noexcept -> size_type
diff --git a/src/expression2/IGCObject_DLambdaExpr.cpp b/src/expression2/IGCObject_DLambdaExpr.cpp
index bfe386a2..c0a95847 100644
--- a/src/expression2/IGCObject_DLambdaExpr.cpp
+++ b/src/expression2/IGCObject_DLambdaExpr.cpp
@@ -22,9 +22,9 @@ namespace xo {
         }
 
         auto
-        IGCObject_DLambdaExpr::shallow_move(DLambdaExpr & self, obj<AAllocator> mm) noexcept -> Opaque
+        IGCObject_DLambdaExpr::shallow_move(DLambdaExpr & self, obj<ACollector> gc) noexcept -> Opaque
         {
-            return self.shallow_move(mm);
+            return self.shallow_move(gc);
         }
         auto
         IGCObject_DLambdaExpr::forward_children(DLambdaExpr & self, obj<ACollector> gc) noexcept -> size_type
diff --git a/src/expression2/IGCObject_DLocalSymtab.cpp b/src/expression2/IGCObject_DLocalSymtab.cpp
index 7078db9a..02941925 100644
--- a/src/expression2/IGCObject_DLocalSymtab.cpp
+++ b/src/expression2/IGCObject_DLocalSymtab.cpp
@@ -22,9 +22,9 @@ namespace xo {
         }
 
         auto
-        IGCObject_DLocalSymtab::shallow_move(DLocalSymtab & self, obj<AAllocator> mm) noexcept -> Opaque
+        IGCObject_DLocalSymtab::shallow_move(DLocalSymtab & self, obj<ACollector> gc) noexcept -> Opaque
         {
-            return self.shallow_move(mm);
+            return self.shallow_move(gc);
         }
         auto
         IGCObject_DLocalSymtab::forward_children(DLocalSymtab & self, obj<ACollector> gc) noexcept -> size_type
diff --git a/src/expression2/IGCObject_DSequenceExpr.cpp b/src/expression2/IGCObject_DSequenceExpr.cpp
index 446a78bb..93af6f10 100644
--- a/src/expression2/IGCObject_DSequenceExpr.cpp
+++ b/src/expression2/IGCObject_DSequenceExpr.cpp
@@ -22,9 +22,9 @@ namespace xo {
         }
 
         auto
-        IGCObject_DSequenceExpr::shallow_move(DSequenceExpr & self, obj<AAllocator> mm) noexcept -> Opaque
+        IGCObject_DSequenceExpr::shallow_move(DSequenceExpr & self, obj<ACollector> gc) noexcept -> Opaque
         {
-            return self.shallow_move(mm);
+            return self.shallow_move(gc);
         }
         auto
         IGCObject_DSequenceExpr::forward_children(DSequenceExpr & self, obj<ACollector> gc) noexcept -> size_type
diff --git a/src/expression2/IGCObject_DTypename.cpp b/src/expression2/IGCObject_DTypename.cpp
index 154a8b4a..58df5bff 100644
--- a/src/expression2/IGCObject_DTypename.cpp
+++ b/src/expression2/IGCObject_DTypename.cpp
@@ -22,9 +22,9 @@ namespace xo {
         }
 
         auto
-        IGCObject_DTypename::shallow_move(DTypename & self, obj<AAllocator> mm) noexcept -> Opaque
+        IGCObject_DTypename::shallow_move(DTypename & self, obj<ACollector> gc) noexcept -> Opaque
         {
-            return self.shallow_move(mm);
+            return self.shallow_move(gc);
         }
         auto
         IGCObject_DTypename::forward_children(DTypename & self, obj<ACollector> gc) noexcept -> size_type
diff --git a/src/expression2/IGCObject_DVarRef.cpp b/src/expression2/IGCObject_DVarRef.cpp
index b6b5e077..64967c9b 100644
--- a/src/expression2/IGCObject_DVarRef.cpp
+++ b/src/expression2/IGCObject_DVarRef.cpp
@@ -22,9 +22,9 @@ namespace xo {
         }
 
         auto
-        IGCObject_DVarRef::shallow_move(DVarRef & self, obj<AAllocator> mm) noexcept -> Opaque
+        IGCObject_DVarRef::shallow_move(DVarRef & self, obj<ACollector> gc) noexcept -> Opaque
         {
-            return self.shallow_move(mm);
+            return self.shallow_move(gc);
         }
         auto
         IGCObject_DVarRef::forward_children(DVarRef & self, obj<ACollector> gc) noexcept -> size_type
diff --git a/src/expression2/facet/IGCObject_DVariable.cpp b/src/expression2/facet/IGCObject_DVariable.cpp
index 8a49292b..d418145c 100644
--- a/src/expression2/facet/IGCObject_DVariable.cpp
+++ b/src/expression2/facet/IGCObject_DVariable.cpp
@@ -22,9 +22,9 @@ namespace xo {
         }
 
         auto
-        IGCObject_DVariable::shallow_move(DVariable & self, obj<AAllocator> mm) noexcept -> Opaque
+        IGCObject_DVariable::shallow_move(DVariable & self, obj<ACollector> gc) noexcept -> Opaque
         {
-            return self.shallow_move(mm);
+            return self.shallow_move(gc);
         }
         auto
         IGCObject_DVariable::forward_children(DVariable & self, obj<ACollector> gc) noexcept -> size_type