From 79586af2faaa56d92ca006b0623d9346963c4c5a Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Thu, 5 Mar 2026 20:11:05 +1100
Subject: [PATCH] xo-object2 stack: refactor/tidy after GCObject -> alloc2

---
 include/xo/gc/GCObjectConversion.hpp          | 117 ------------------
 .../xo/gc/detail/ICollector_DX1Collector.hpp  |   2 +
 2 files changed, 2 insertions(+), 117 deletions(-)
 delete mode 100644 include/xo/gc/GCObjectConversion.hpp

diff --git a/include/xo/gc/GCObjectConversion.hpp b/include/xo/gc/GCObjectConversion.hpp
deleted file mode 100644
index 59ec12f..0000000
--- a/include/xo/gc/GCObjectConversion.hpp
+++ /dev/null
@@ -1,117 +0,0 @@
-/** @file GCObjectConversion.hpp
- *
- *  @author Roland Conybeare, Jan 2026
- **/
-
-#pragma once
-
-#include <xo/alloc2/GCObject.hpp>
-#include <xo/alloc2/Allocator.hpp>
-#include <xo/facet/FacetRegistry.hpp>
-#include <xo/facet/obj.hpp>
-#include <xo/indentlog/scope.hpp>
-
-namespace xo {
-    namespace scm {
-        /** @brief compile-time conversion obj<AGCObject> <-> T
-         *
-         *  Specialize for each T that participates in conversion.
-         *  Methods here aren't implemented
-         **/
-        template <typename T>
-        struct GCObjectConversion {
-            using AGCObject = xo::mm::AGCObject;
-            using AAllocator = xo::mm::AAllocator;
-
-            /** find gc-aware representation for @p x.
-             *  If necessary allocate from @p mm, but may
-             *  refer to @p x in-place
-             **/
-            static obj<AGCObject> to_gco(obj<AAllocator> mm, const T & x);
-            /** convert to native representation @tparam T from gc-aware
-             *  @p gco.  If necessary allocate from @p mm, but
-             *  may instead refer to @p x in-place
-             **/
-            static T from_gco(obj<AAllocator> mm, obj<AGCObject> gco);
-        };
-
-        /** Motivating use-case for GCObjectConversion is to transform
-         *  primitive function arguments and results to/from gc-aware
-         *  representation.
-         *
-         *  However: Schematika also supports runtime polymorphism
-         *  which leads to primitives that expect obj<AFacet> arguments.
-         *
-         *  Also, Schematika expression parser needs representation for
-         *  expressions, before type unification.
-         *
-         *  Consider a function like:
-         *    def fact = lambda (n : i64) { if (n <= 0) then 1 else (n * fact(n - 1)); }
-         *  During expression parsing the rhs argument to multiply has unknown type.
-         *  To construct an expression for input to unification will use polymorphic
-         *  binding for multiply primitive, relying on specialization here for
-         *  its implementation.
-         **/
-        template <typename AFacet, typename DRepr>
-        struct GCObjectConversion<obj<AFacet,DRepr>> {
-            using AGCObject = xo::mm::AGCObject;
-            using AAllocator = xo::mm::AAllocator;
-            using FacetRegistry = xo::facet::FacetRegistry;
-            using DVariantPlaceholder = xo::facet::DVariantPlaceholder;
-
-            static obj<AGCObject> to_gco(obj<AAllocator>,
-                                         obj<AFacet,DRepr> gco) {
-                if constexpr (std::is_same_v<AFacet, AGCObject>) {
-                    // trivial conversion!
-                    return gco;
-                } else if constexpr (std::is_same_v<DRepr, DVariantPlaceholder>) {
-                    // runtime polymorphism
-                    return FacetRegistry::instance().variant<AGCObject,AFacet>(gco);
-                } else /* DRepr != DVariantPlaceholder */ {
-                    // known content w/ fat object pointer
-                    return obj<AGCObject,DRepr>(gco.data());
-                }
-            }
-
-            static obj<AFacet,DRepr> from_gco(obj<AAllocator>,
-                                              obj<AGCObject> gco) {
-                scope log(XO_DEBUG(false));
-
-                if constexpr (std::is_same_v<AFacet, AGCObject>) {
-                    // Need accurate handling of DVariantPlaceholder.
-                    // runtime type must be some concrete type.
-                    // Only use obj<AFacet,DRepr>::from when DRepr is a concrete type
-
-                    if constexpr (std::is_same_v<DRepr,DVariantPlaceholder>) {
-                        // At comptime gco has unknown repr.  At runtime
-                        // will have some known repr, which assignment here will transfer
-                        return gco;
-                    } else {
-                        // Runtime conversion to concrete type DRepr
-
-                        auto retval = obj<AFacet,DRepr>::from(gco);
-
-                        if (!retval) {
-                            log.retroactively_enable();
-
-                            log && log(xtag("gco.tseq", gco._typeseq()));
-                            log && log(xtag("DRepr.tseq", reflect::typeseq::id<DRepr>()));
-                        }
-
-                        assert(retval);
-
-                        return retval;
-                    }
-                } else {
-                    // both runtime and comptime polymorphism
-                    // use same path here, since representation of @p gco
-                    // is type-erased here
-
-                    return FacetRegistry::instance().variant<AFacet,AGCObject>(gco);
-                }
-            }
-        };
-    } /*namespace scm */
-} /*namespace xo*/
-
-/* end GCObjectConversion.hpp */
diff --git a/include/xo/gc/detail/ICollector_DX1Collector.hpp b/include/xo/gc/detail/ICollector_DX1Collector.hpp
index 0475a53..1db50e2 100644
--- a/include/xo/gc/detail/ICollector_DX1Collector.hpp
+++ b/include/xo/gc/detail/ICollector_DX1Collector.hpp
@@ -3,6 +3,8 @@
  *  @author Roland Conybeare, Dec 2025
  **/
 
+#pragma once
+
 #include <xo/alloc2/gc/ACollector.hpp>
 #include <xo/alloc2/gc/ICollector_Xfer.hpp>
 #include "DX1Collector.hpp"