From 48a51628b841a9b69db846326dcaa67239a8559f Mon Sep 17 00:00:00 2001
From: Eugen Wissner <belka@caraus.de>
Date: Sun, 1 Nov 2026 22:10:48 +0100
Subject: Fix generic inference for a procedure call as a slice base

---
 boot/symbol.cc | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)

(limited to 'boot/symbol.cc')

diff --git a/boot/symbol.cc b/boot/symbol.cc
index 310ae8a..dcbd460 100644
--- a/boot/symbol.cc
+++ b/boot/symbol.cc
@@ -700,6 +700,103 @@ namespace elna::boot
         return subject;
     }
 
+    bool bind_arguments(const std::vector<type>& parameters, std::vector<type>& bindings,
+            const type& declared, const type& actual)
+    {
+        const type left = resolve_aliases(declared);
+        const type right = resolve_aliases(actual);
+
+        if (const auto parameter = left.get<parameter_type>())
+        {
+            for (std::size_t i = 0; i < parameters.size(); ++i)
+            {
+                if (parameters[i].get<parameter_type>() == parameter && bindings[i].empty())
+                {
+                    // The actual type is recorded as it stands, which inside a
+                    // generic body may itself be an abstract parameter.
+                    bindings[i] = actual;
+                }
+            }
+            return true;
+        }
+        else if (const auto left_pointer = left.get<pointer_type>())
+        {
+            const std::shared_ptr<pointer_type> right_pointer = right.get<pointer_type>();
+
+            return right_pointer != nullptr
+                && bind_arguments(parameters, bindings, left_pointer->base, right_pointer->base);
+        }
+        else if (const auto left_slice = left.get<slice_type>())
+        {
+            const std::shared_ptr<slice_type> right_slice = right.get<slice_type>();
+
+            return right_slice != nullptr
+                && bind_arguments(parameters, bindings, left_slice->base, right_slice->base);
+        }
+        else if (const auto left_array = left.get<array_type>())
+        {
+            const std::shared_ptr<array_type> right_array = right.get<array_type>();
+
+            return right_array != nullptr
+                && bind_arguments(parameters, bindings, left_array->base, right_array->base);
+        }
+        else if (const auto left_constant = left.get<constant_type>())
+        {
+            const std::shared_ptr<constant_type> right_constant = right.get<constant_type>();
+            const type right_unqualified = right_constant != nullptr
+                ? right_constant->unqualified
+                : right;
+
+            return bind_arguments(parameters, bindings, left_constant->unqualified, right_unqualified);
+        }
+        else if (const auto left_instance = left.get<instantiated_type>())
+        {
+            for (type candidate = right; !candidate.empty(); candidate = base_of(candidate))
+            {
+                const std::shared_ptr<instantiated_type> right_instance =
+                    resolve_aliases(candidate).get<instantiated_type>();
+
+                if (right_instance == nullptr
+                        || !(left_instance->generic == right_instance->generic)
+                        || left_instance->arguments.size() != right_instance->arguments.size())
+                {
+                    continue;
+                }
+                for (std::size_t i = 0; i < left_instance->arguments.size(); ++i)
+                {
+                    if (!bind_arguments(parameters, bindings,
+                                left_instance->arguments.at(i), right_instance->arguments.at(i)))
+                    {
+                        return false;
+                    }
+                }
+                return true;
+            }
+            return false;
+        }
+        else if (const auto left_procedure = left.get<procedure_type>())
+        {
+            const std::shared_ptr<procedure_type> right_procedure = right.get<procedure_type>();
+
+            if (right_procedure == nullptr
+                    || left_procedure->parameters.size() != right_procedure->parameters.size())
+            {
+                return false;
+            }
+            for (std::size_t i = 0; i < left_procedure->parameters.size(); ++i)
+            {
+                if (!bind_arguments(parameters, bindings,
+                            left_procedure->parameters.at(i), right_procedure->parameters.at(i)))
+                {
+                    return false;
+                }
+            }
+            return left_procedure->return_type.empty()
+                || bind_arguments(parameters, bindings, left_procedure->return_type, right_procedure->return_type);
+        }
+        return true;
+    }
+
     type instantiate(const std::shared_ptr<instantiated_type>& instance)
     {
         std::shared_ptr<generic_type> const generic = unwrap_generic(instance->generic);
-- 
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