From dd64b61e51fe3b9d3f818a1a5c2e6c5100e3ba43 Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Fri, 30 Jan 2026 12:41:09 -0500
Subject: [PATCH] xo-reader2: + assemble lambda function type in DLambdaSsm

---
 include/xo/expression2/DLambdaExpr.hpp |  8 +++++++
 src/expression2/DLambdaExpr.cpp        | 29 ++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/include/xo/expression2/DLambdaExpr.hpp b/include/xo/expression2/DLambdaExpr.hpp
index bd9ff2c5..14be115f 100644
--- a/include/xo/expression2/DLambdaExpr.hpp
+++ b/include/xo/expression2/DLambdaExpr.hpp
@@ -47,6 +47,14 @@ namespace xo {
                                        const DUniqueString * name,
                                        DLocalSymtab * local_symtab,
                                        obj<AExpression> body);
+
+            /** create type description for lambda with arguments described by @p symtab
+             *  and return type @p return_td.
+             *  Load-bearing for DLambdaSsm in xo-reader2/
+             **/
+            static TypeDescr assemble_lambda_td(DLocalSymtab * symtab,
+                                                TypeDescr return_td);
+
             ///@}
             /** @defgroup scm-lambdaexpr-methods **/
             ///@{
diff --git a/src/expression2/DLambdaExpr.cpp b/src/expression2/DLambdaExpr.cpp
index fec939ac..a27e788b 100644
--- a/src/expression2/DLambdaExpr.cpp
+++ b/src/expression2/DLambdaExpr.cpp
@@ -14,6 +14,8 @@ namespace xo {
     using xo::print::APrintable;
     using xo::facet::FacetRegistry;
     using xo::reflect::TypeDescr;
+    using xo::reflect::TypeDescrBase;
+    using xo::reflect::FunctionTdxInfo;
     using xo::reflect::typeseq;
 
     namespace scm {
@@ -82,6 +84,33 @@ namespace xo {
                                          body);
         }
 
+        TypeDescr
+        DLambdaExpr::assemble_lambda_td(DLocalSymtab * symtab,
+                                        TypeDescr return_td)
+        {
+            assert(return_td);
+
+            std::vector<TypeDescr> arg_td_v;
+            {
+                DLocalSymtab::size_type z = symtab->size();
+
+                arg_td_v.reserve(z);
+
+                for (DLocalSymtab::size_type i = 0; i < z; ++i) {
+                    auto param = symtab->lookup_var(Binding::local(i));
+
+                    assert(param);
+                    arg_td_v.push_back(param->valuetype());
+                }
+            }
+
+            auto function_tdx = FunctionTdxInfo(return_td, arg_td_v, false /*!is_noexcept*/);
+
+            TypeDescr lambda_td = TypeDescrBase::require_by_fn_info(function_tdx);
+
+            return lambda_td;
+        }
+
         exprtype
         DLambdaExpr::extype() const noexcept {
             return exprtype::lambda;