From 5fb6afc2e1dba6a56c59440309bd6786296fba8e Mon Sep 17 00:00:00 2001
From: Eduard Staniloiu <edi33416@gmail.com>
Date: Wed, 17 Apr 2019 00:03:54 +0300
Subject: [PATCH] Lower CmpExp between classes to __cmp call

---
 src/dmd/expressionsem.d | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/dmd/expressionsem.d b/src/dmd/expressionsem.d
index 48e47cef2508..e4d394084c44 100644
--- a/src/dmd/expressionsem.d
+++ b/src/dmd/expressionsem.d
@@ -11333,6 +11333,24 @@ private extern (C++) final class ExpressionSemanticVisitor : Visitor
             return setError();
         }
 
+        if (t1.ty == Tclass && t2.ty == Tclass)
+        {
+            // Lower to object.__cmp(e1, e2)
+            Expression cl = new IdentifierExp(exp.loc, Id.empty);
+            cl = new DotIdExp(exp.loc, cl, Id.object);
+            cl = new DotIdExp(exp.loc, cl, Id.__cmp);
+            cl = cl.expressionSemantic(sc);
+
+            auto arguments = new Expressions();
+            arguments.push(exp.e1);
+            arguments.push(exp.e2);
+
+            cl = new CallExp(exp.loc, cl, arguments);
+            cl = new CmpExp(exp.op, exp.loc, cl, new IntegerExp(0));
+            result = cl.expressionSemantic(sc);
+            return;
+        }
+
         EXP cmpop;
         if (auto e = exp.op_overload(sc, &cmpop))
         {