From 16dd7e365af22aa500070fb5c3b4cdf7139db1d2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lu=C3=ADs=20Ferreira?= <contact@lsferreira.net>
Date: Sun, 16 Oct 2022 20:25:44 +0100
Subject: [PATCH] chore(sumtype): avoid quadratic memory complexity on opEquals
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Signed-off-by: Luís Ferreira <contact@lsferreira.net>
---
 std/sumtype.d | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/std/sumtype.d b/std/sumtype.d
index ee2d73a1233..715a4119404 100644
--- a/std/sumtype.d
+++ b/std/sumtype.d
@@ -714,16 +714,24 @@ public:
     {
         static if (is(This == Rhs))
         {
-            return AliasSeq!(this, rhs).match!((ref value, ref rhsValue) {
-                static if (is(typeof(value) == typeof(rhsValue)))
-                {
-                    return value == rhsValue;
-                }
-                else
+            final switch(tag)
+            {
+                static foreach(idx, T; Types)
                 {
-                    return false;
+                    case idx:
+                        final switch (rhs.tag)
+                        {
+                            static foreach(ridx, U; typeof(rhs).Types)
+                            {
+                                case ridx:
+                                    static if (is(immutable T == immutable U))
+                                        return get!T == rhs.get!U;
+                                    else
+                                        return false;
+                            }
+                        }
                 }
-            });
+            }
         }
         else
         {