From e676e74efbbbf62887b9442326399eebccc4d108 Mon Sep 17 00:00:00 2001
From: Eugen Wissner <belka@caraus.de>
Date: Fri, 17 Jul 2026 16:16:23 +0200
Subject: Handle base type constness

---
 boot/symbol.cc                              | 289 +++++++---------------------
 boot/type_check.cc                          |   5 +-
 gcc/gcc/elna-builtins.cc                    |   2 +-
 include/elna/boot/symbol.h                  |  58 ++----
 testsuite/compilable/record_const_base.elna |  18 ++
 5 files changed, 105 insertions(+), 267 deletions(-)
 create mode 100644 testsuite/compilable/record_const_base.elna

diff --git a/boot/symbol.cc b/boot/symbol.cc
index bd6ec49..6ad89b7 100644
--- a/boot/symbol.cc
+++ b/boot/symbol.cc
@@ -19,224 +19,72 @@ along with GCC; see the file COPYING3.  If not see
 
 namespace elna::boot
 {
-    type::type()
-    {
-    }
-
     type::type(std::shared_ptr<alias_type> alias)
-        : tag(type_tag::alias), alias(alias)
+        : payload(alias)
     {
     }
 
     type::type(std::shared_ptr<primitive_type> primitive)
-        : tag(type_tag::primitive), primitive(primitive)
+        : payload(primitive)
     {
     }
 
     type::type(std::shared_ptr<record_type> record)
-        : tag(type_tag::record), record(record)
+        : payload(record)
     {
     }
 
     type::type(std::shared_ptr<pointer_type> pointer)
-        : tag(type_tag::pointer), pointer(pointer)
+        : payload(pointer)
     {
     }
 
     type::type(std::shared_ptr<constant_type> constant)
-        : tag(type_tag::constant), constant(constant)
+        : payload(constant)
     {
     }
 
     type::type(std::shared_ptr<array_type> array)
-        : tag(type_tag::array), array(array)
+        : payload(array)
     {
     }
 
     type::type(std::shared_ptr<procedure_type> procedure)
-        : tag(type_tag::procedure), procedure(procedure)
+        : payload(procedure)
     {
     }
 
     type::type(std::shared_ptr<enumeration_type> enumeration)
-        : tag(type_tag::enumeration), enumeration(enumeration)
+        : payload(enumeration)
     {
     }
 
-    void type::copy(const type& other)
+    template<typename T>
+    std::shared_ptr<T> type::get() const
     {
-        switch (other.tag)
+        if constexpr (std::is_same_v<T, alias_type>)
         {
-        case type_tag::empty:
-            break;
-        case type_tag::alias:
-            new (&alias) std::weak_ptr<alias_type>(other.alias);
-            break;
-        case type_tag::primitive:
-            new (&primitive) std::shared_ptr<primitive_type>(other.primitive);
-            break;
-        case type_tag::record:
-            new (&record) std::shared_ptr<record_type>(other.record);
-            break;
-        case type_tag::pointer:
-            new (&pointer) std::shared_ptr<pointer_type>(other.pointer);
-            break;
-        case type_tag::constant:
-            new (&constant) std::shared_ptr<constant_type>(other.constant);
-            break;
-        case type_tag::array:
-            new (&array) std::shared_ptr<array_type>(other.array);
-            break;
-        case type_tag::procedure:
-            new (&procedure) std::shared_ptr<procedure_type>(other.procedure);
-            break;
-        case type_tag::enumeration:
-            new (&enumeration) std::shared_ptr<enumeration_type>(other.enumeration);
-            break;
+            if (auto *wp = std::get_if<std::weak_ptr<alias_type>>(&payload))
+                return wp->lock();
+            return nullptr;
         }
-    }
-
-    type::type(const type& other)
-        : tag(other.tag)
-    {
-        copy(other);
-    }
-
-    void type::move(type&& other)
-    {
-        switch (other.tag)
-        {
-        case type_tag::empty:
-            break;
-        case type_tag::alias:
-            new (&alias) std::weak_ptr<alias_type>(std::move(other.alias));
-            break;
-        case type_tag::primitive:
-            new (&primitive) std::shared_ptr<primitive_type>(std::move(other.primitive));
-            break;
-        case type_tag::record:
-            new (&record) std::shared_ptr<record_type>(std::move(other.record));
-            break;
-        case type_tag::pointer:
-            new (&pointer) std::shared_ptr<pointer_type>(std::move(other.pointer));
-            break;
-        case type_tag::constant:
-            new (&constant) std::shared_ptr<constant_type>(std::move(other.constant));
-            break;
-        case type_tag::array:
-            new (&array) std::shared_ptr<array_type>(std::move(other.array));
-            break;
-        case type_tag::procedure:
-            new (&procedure) std::shared_ptr<procedure_type>(std::move(other.procedure));
-            break;
-        case type_tag::enumeration:
-            new (&enumeration) std::shared_ptr<enumeration_type>(std::move(other.enumeration));
-            break;
-        }
-    }
-
-    type& type::operator=(const type& other)
-    {
-        this->~type();
-        this->tag = other.tag;
-        copy(other);
-        return *this;
-    }
-
-    type::type(type&& other)
-        : tag(other.tag)
-    {
-        move(std::move(other));
-    }
-
-    type& type::operator=(type&& other)
-    {
-        this->~type();
-        this->tag = other.tag;
-        move(std::move(other));
-        return *this;
-    }
-
-    type::~type()
-    {
-        switch (tag)
+        else
         {
-        case type_tag::empty:
-            break;
-        case type_tag::alias:
-            this->alias.~weak_ptr<alias_type>();
-            break;
-        case type_tag::primitive:
-            this->primitive.~shared_ptr<primitive_type>();
-            break;
-        case type_tag::record:
-            this->record.~shared_ptr<record_type>();
-            break;
-        case type_tag::pointer:
-            this->pointer.~shared_ptr<pointer_type>();
-            break;
-        case type_tag::constant:
-            this->constant.~shared_ptr<constant_type>();
-            break;
-        case type_tag::array:
-            this->array.~shared_ptr<array_type>();
-            break;
-        case type_tag::procedure:
-            this->procedure.~shared_ptr<procedure_type>();
-            break;
-        case type_tag::enumeration:
-            this->enumeration.~shared_ptr<enumeration_type>();
-            break;
+            if (auto *sp = std::get_if<std::shared_ptr<T>>(&payload))
+                return *sp;
+            return nullptr;
         }
     }
 
-    template<>
-    std::shared_ptr<alias_type> type::get<alias_type>() const
-    {
-        return tag == type_tag::alias ? this->alias.lock() : nullptr;
-    }
-
-    template<>
-    std::shared_ptr<primitive_type> type::get<primitive_type>() const
-    {
-        return tag == type_tag::primitive ? this->primitive : nullptr;
-    }
-
-    template<>
-    std::shared_ptr<record_type> type::get<record_type>() const
-    {
-        return tag == type_tag::record ? this->record : nullptr;
-    }
-
-    template<>
-    std::shared_ptr<pointer_type> type::get<pointer_type>() const
-    {
-        return tag == type_tag::pointer ? this->pointer : nullptr;
-    }
-
-    template<>
-    std::shared_ptr<array_type> type::get<array_type>() const
-    {
-        return tag == type_tag::array ? this->array : nullptr;
-    }
-
-    template<>
-    std::shared_ptr<constant_type> type::get<constant_type>() const
-    {
-        return tag == type_tag::constant ? this->constant : nullptr;
-    }
-
-    template<>
-    std::shared_ptr<procedure_type> type::get<procedure_type>() const
-    {
-        return tag == type_tag::procedure ? this->procedure : nullptr;
-    }
-
-    template<>
-    std::shared_ptr<enumeration_type> type::get<enumeration_type>() const
-    {
-        return tag == type_tag::enumeration ? this->enumeration : nullptr;
-    }
+    // Explicit instantiation for all types used by callers.
+    template std::shared_ptr<alias_type> type::get<alias_type>() const;
+    template std::shared_ptr<primitive_type> type::get<primitive_type>() const;
+    template std::shared_ptr<record_type> type::get<record_type>() const;
+    template std::shared_ptr<pointer_type> type::get<pointer_type>() const;
+    template std::shared_ptr<array_type> type::get<array_type>() const;
+    template std::shared_ptr<constant_type> type::get<constant_type>() const;
+    template std::shared_ptr<procedure_type> type::get<procedure_type>() const;
+    template std::shared_ptr<enumeration_type> type::get<enumeration_type>() const;
 
     bool type::operator==(const std::nullptr_t&) const
     {
@@ -293,61 +141,54 @@ namespace elna::boot
 
     bool type::empty() const
     {
-        return tag == type_tag::empty;
+        return std::holds_alternative<std::monostate>(payload);
     }
 
     std::string type::to_string() const
     {
-        switch (tag)
-        {
-            case type_tag::empty:
+        return std::visit([](const auto& p) -> std::string {
+            using T = std::decay_t<decltype(p)>;
+            if constexpr (std::is_same_v<T, std::monostate>)
                 return "<empty>";
-            case type_tag::alias:
-                return alias.lock()->name;
-            case type_tag::primitive:
-                return primitive->identifier;
-            case type_tag::pointer:
-                return "^" + pointer->base.to_string();
-            case type_tag::constant:
-                return "const " + constant->unqualified.to_string();
-            case type_tag::array:
-                return "[" + std::to_string(array->size) + "]" + array->base.to_string();
-            case type_tag::record:
-                if (record->base.empty())
-                {
+            else if constexpr (std::is_same_v<T, std::weak_ptr<alias_type>>)
+                return p.lock()->name;
+            else if constexpr (std::is_same_v<T, std::shared_ptr<primitive_type>>)
+                return p->identifier;
+            else if constexpr (std::is_same_v<T, std::shared_ptr<pointer_type>>)
+                return "^" + p->base.to_string();
+            else if constexpr (std::is_same_v<T, std::shared_ptr<constant_type>>)
+                return "const " + p->unqualified.to_string();
+            else if constexpr (std::is_same_v<T, std::shared_ptr<array_type>>)
+                return "[" + std::to_string(p->size) + "]" + p->base.to_string();
+            else if constexpr (std::is_same_v<T, std::shared_ptr<record_type>>)
+            {
+                if (p->base.empty())
                     return "record ... end";
-                }
                 else
+                    return "record(" + p->base.to_string() + ") ... end";
+            }
+            else if constexpr (std::is_same_v<T, std::shared_ptr<procedure_type>>)
+            {
+                std::string result = "proc(";
+                for (std::size_t i = 0; i < p->parameters.size(); ++i)
                 {
-                    return "record(" + record->base.to_string() + ") ... end";
-                }
-            case type_tag::procedure:
-                {
-                    std::string result = "proc(";
-                    for (std::size_t i = 0; i < procedure->parameters.size(); ++i)
-                    {
-                        if (i > 0) result += ", ";
-                        result += procedure->parameters[i].to_string();
-                    }
-                    result += ")";
-                    if (procedure->return_type.no_return)
-                    {
-                        result += ": !";
-                    }
-                    else if (!procedure->return_type.proper_type.empty())
-                    {
-                        result += ": " + procedure->return_type.proper_type.to_string();
-                    }
-                    return result;
+                    if (i > 0) result += ", ";
+                    result += p->parameters[i].to_string();
                 }
-            case type_tag::enumeration:
+                result += ")";
+                if (p->return_type.no_return)
+                    result += ": !";
+                else if (!p->return_type.proper_type.empty())
+                    result += ": " + p->return_type.proper_type.to_string();
+                return result;
+            }
+            else if constexpr (std::is_same_v<T, std::shared_ptr<enumeration_type>>)
                 return "(enumeration)";
-        }
-        __builtin_unreachable();
+        }, payload);
     }
 
     alias_type::alias_type(const std::string& name)
-        : name(name), reference()
+        : name(name), referent()
     {
     }
 
@@ -517,7 +358,7 @@ namespace elna::boot
     {
         auto unresolved_declaration = this->unresolved.at(symbol_name);
 
-        unresolved_declaration->reference = resolution;
+        unresolved_declaration->referent = resolution;
         return unresolved_declaration;
     }
 
@@ -544,7 +385,7 @@ namespace elna::boot
 
     type resolve_underlying_type(std::shared_ptr<alias_type> alias)
     {
-        return resolve_underlying_type(alias->reference);
+        return resolve_underlying_type(alias->referent);
     }
 
     type resolve_underlying_type(const type& alias)
@@ -565,7 +406,7 @@ namespace elna::boot
     {
         if (auto alias = checked.get<alias_type>())
         {
-            return resolve_aliases(alias->reference);
+            return resolve_aliases(alias->referent);
         }
         return checked;
     }
diff --git a/boot/type_check.cc b/boot/type_check.cc
index 3667007..b42792b 100644
--- a/boot/type_check.cc
+++ b/boot/type_check.cc
@@ -212,7 +212,8 @@ namespace elna::boot
                     return true;
                 }
             }
-            return !record->base.empty() && contains_constant_member(record->base);
+            return !record->base.empty()
+                && contains_constant_member(resolve_underlying_type(record->base));
         }
         else if (auto array = referent.get<array_type>())
         {
@@ -230,7 +231,7 @@ namespace elna::boot
         }
         alias_path.push_back(alias->name);
 
-        if (auto another_alias = alias->reference.get<alias_type>())
+        if (auto another_alias = alias->referent.get<alias_type>())
         {
             return check_unresolved_symbol(another_alias, alias_path);
         }
diff --git a/gcc/gcc/elna-builtins.cc b/gcc/gcc/elna-builtins.cc
index 3c424f8..5284563 100644
--- a/gcc/gcc/elna-builtins.cc
+++ b/gcc/gcc/elna-builtins.cc
@@ -178,7 +178,7 @@ namespace elna::gcc
 
         if (looked_up == NULL_TREE)
         {
-            tree type_tree = get_inner_alias(reference->reference, symbols);
+            tree type_tree = get_inner_alias(reference->referent, symbols);
             looked_up = build_decl(UNKNOWN_LOCATION, TYPE_DECL,
                     get_identifier(symbol_name.c_str()), type_tree);
 
diff --git a/include/elna/boot/symbol.h b/include/elna/boot/symbol.h
index 6884dd7..216021e 100644
--- a/include/elna/boot/symbol.h
+++ b/include/elna/boot/symbol.h
@@ -18,11 +18,12 @@ along with GCC; see the file COPYING3.  If not see
 #pragma once
 
 #include <cstdint>
-#include <unordered_map>
-#include <string>
+#include <forward_list>
 #include <memory>
+#include <string>
+#include <unordered_map>
+#include <variant>
 #include <vector>
-#include <forward_list>
 
 #include "elna/boot/result.h"
 
@@ -39,36 +40,21 @@ namespace elna::boot
 
     class type
     {
-        enum class type_tag
-        {
-            empty,
-            alias,
-            primitive,
-            record,
-            pointer,
-            constant,
-            array,
-            procedure,
-            enumeration
-        };
-        type_tag tag{ type_tag::empty };
-        union
-        {
-            std::weak_ptr<alias_type> alias;
-            std::shared_ptr<primitive_type> primitive;
-            std::shared_ptr<record_type> record;
-            std::shared_ptr<pointer_type> pointer;
-            std::shared_ptr<constant_type> constant;
-            std::shared_ptr<array_type> array;
-            std::shared_ptr<procedure_type> procedure;
-            std::shared_ptr<enumeration_type> enumeration;
-        };
-
-        void copy(const type& other);
-        void move(type&& other);
+        std::variant<
+            std::monostate,
+            std::weak_ptr<alias_type>,
+            std::shared_ptr<primitive_type>,
+            std::shared_ptr<record_type>,
+            std::shared_ptr<pointer_type>,
+            std::shared_ptr<constant_type>,
+            std::shared_ptr<array_type>,
+            std::shared_ptr<procedure_type>,
+            std::shared_ptr<enumeration_type>
+        > payload;
 
     public:
-        type();
+        type() = default;
+
         explicit type(std::shared_ptr<alias_type> alias);
         explicit type(std::shared_ptr<primitive_type> primitive);
         explicit type(std::shared_ptr<record_type> record);
@@ -78,14 +64,6 @@ namespace elna::boot
         explicit type(std::shared_ptr<procedure_type> procedure);
         explicit type(std::shared_ptr<enumeration_type> enumeration);
 
-        type(const type& other);
-        type& operator=(const type& other);
-
-        type(type&& other);
-        type& operator=(type&& other);
-
-        ~type();
-
         template<typename T>
         std::shared_ptr<T> get() const;
 
@@ -104,7 +82,7 @@ namespace elna::boot
     struct alias_type
     {
         const std::string name;
-        type reference;
+        type referent;
 
         explicit alias_type(const std::string& name);
     };
diff --git a/testsuite/compilable/record_const_base.elna b/testsuite/compilable/record_const_base.elna
new file mode 100644
index 0000000..f24d27b
--- /dev/null
+++ b/testsuite/compilable/record_const_base.elna
@@ -0,0 +1,18 @@
+type
+  B = record
+    x: Int
+  end
+  CB = const B
+  D = record(CB)
+    y: Int
+  end
+
+proc f()
+var
+  d: D
+begin
+  d.x := 1;
+  d.y := 2
+return
+
+end.
-- 
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