From b0e9b27f5b7ad1c7261c68ad63c2b8463d74649b Mon Sep 17 00:00:00 2001
From: Dennis Korpel <dkorpel@gmail.com>
Date: Fri, 28 Aug 2026 13:17:11 +0200
Subject: [PATCH] Fix #23731 - undefined __xopEquals/__xtoHash for instantiated
 struct

786dc71ad7 stopped emitting the special TypeInfo members alongside the
TypeInfo of a template-instantiated struct whose own codegen was elided,
assuming they are always emitted with the StructDeclaration elsewhere.

That does not hold when `ti.minst` is null (a speculative instance whose
TypeInfo was requested anyway) or a non-root module that is not part of
the compilation: nothing emits `TemplateInstance.toObjFile()`, so the
TypeInfo emitted here is left referencing symbols no object file defines.

Restore emitting them next to the TypeInfo, as before 2.113.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 compiler/src/dmd/glue/todt.d                | 19 +++++++++++++++++++
 compiler/test/runnable/imports/test23731a.d |  8 ++++++++
 compiler/test/runnable/test23731.d          | 12 ++++++++++++
 3 files changed, 39 insertions(+)
 create mode 100644 compiler/test/runnable/imports/test23731a.d
 create mode 100644 compiler/test/runnable/test23731.d

diff --git a/compiler/src/dmd/glue/todt.d b/compiler/src/dmd/glue/todt.d
index 14f797eac16f..38c48e7cfd4d 100644
--- a/compiler/src/dmd/glue/todt.d
+++ b/compiler/src/dmd/glue/todt.d
@@ -1471,6 +1471,25 @@ private extern (C++) class TypeInfoDtVisitor : Visitor
             semanticTypeInfoMembers(sd);
         }
 
+        if (TemplateInstance ti = sd.isInstantiated())
+        {
+            if (!ti.needsCodegen())
+            {
+                if (sd.xeq && sd.xeq != StructDeclaration.xerreq)
+                    toObjFile(sd.xeq, global.params.multiobj);
+                if (sd.xcmp && sd.xcmp != StructDeclaration.xerrcmp)
+                    toObjFile(sd.xcmp, global.params.multiobj);
+                if (FuncDeclaration ftostr = search_toString(sd))
+                    toObjFile(ftostr, global.params.multiobj);
+                if (sd.xhash)
+                    toObjFile(sd.xhash, global.params.multiobj);
+                if (sd.postblit)
+                    toObjFile(sd.postblit, global.params.multiobj);
+                if (sd.dtor)
+                    toObjFile(sd.dtor, global.params.multiobj);
+            }
+        }
+
         /* Put out:
          *  char[] mangledName;
          *  void[] init;
diff --git a/compiler/test/runnable/imports/test23731a.d b/compiler/test/runnable/imports/test23731a.d
new file mode 100644
index 000000000000..c0386f30a8dc
--- /dev/null
+++ b/compiler/test/runnable/imports/test23731a.d
@@ -0,0 +1,8 @@
+module imports.test23731a;
+
+struct Wrapper(T)
+{
+    T[] values;
+}
+
+enum wrapperIntSize = Wrapper!int.sizeof;
diff --git a/compiler/test/runnable/test23731.d b/compiler/test/runnable/test23731.d
new file mode 100644
index 000000000000..8ed17ebb80f2
--- /dev/null
+++ b/compiler/test/runnable/test23731.d
@@ -0,0 +1,12 @@
+// https://github.com/dlang/dmd/issues/23731
+
+import imports.test23731a;
+
+void main()
+{
+    auto ti = typeid(Wrapper!int);
+    auto a = Wrapper!int([1, 2]);
+    auto b = Wrapper!int([1, 2]);
+    assert(ti.equals(&a, &b));
+    assert(ti.getHash(&a) == ti.getHash(&b));
+}