From ca61268e644f937e60bac31f0de4c56a1641738d Mon Sep 17 00:00:00 2001
From: Daniel Murphy <yebblies@gmail.com>
Date: Mon, 20 Feb 2012 23:24:49 +1100
Subject: [PATCH] Fix Issue 5554 - [qtd] Covariance detection failure

The functions match is A is a base class of B, _or_ if B is a base class of A.
---
 src/func.c              |  9 +++++++--
 test/runnable/xtest46.d | 21 +++++++++++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/src/func.c b/src/func.c
index 40bb05fecd82..95f78f84fdd8 100644
--- a/src/func.c
+++ b/src/func.c
@@ -609,9 +609,14 @@ void FuncDeclaration::semantic(Scope *sc)
                     }
                     if (ti)
                     {
-                        if (tintro && !tintro->equals(ti))
+                        if (tintro)
                         {
-                            error("incompatible covariant types %s and %s", tintro->toChars(), ti->toChars());
+                            if (!tintro->nextOf()->equals(ti->nextOf()) &&
+                                !tintro->nextOf()->isBaseOf(ti->nextOf(), NULL) &&
+                                !ti->nextOf()->isBaseOf(tintro->nextOf(), NULL))
+                            {
+                                error("incompatible covariant types %s and %s", tintro->toChars(), ti->toChars());
+                            }
                         }
                         tintro = ti;
                     }
diff --git a/test/runnable/xtest46.d b/test/runnable/xtest46.d
index 4c986c4d0a0b..3522f95af813 100644
--- a/test/runnable/xtest46.d
+++ b/test/runnable/xtest46.d
@@ -3383,6 +3383,26 @@ ref func2521_7() {
     return val;
 }
 
+/***************************************************/
+
+void test5554()
+{
+    class MA { }
+    class MB : MA { }
+    class MC : MB { }
+
+    class A { abstract MA foo(); }
+    interface I { MB foo(); }
+    class B : A
+    {
+        MC foo() { return null; }
+    }
+    class C : B, I
+    {
+        override MC foo() { return null; }
+    }
+}
+
 /***************************************************/
 // 5962
 
@@ -4730,6 +4750,7 @@ int main()
     test85();
     test86();
     test87();
+    test5554();
     test88();
     test7545();
     test89();