Allow mutable opEquals and show error message for migration

dlang · Jul 9, 2012 · 67aca59 · 67aca59
1 parent 35c0b30
commit 67aca59
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Showing 2 changed files with 68 additions and 4 deletions.
diff --git a/import/object.di b/import/object.di
@@ -45,7 +45,46 @@ class Object
     static Object factory(string classname);
 }
 
-bool opEquals(const Object lhs, const Object rhs);
+bool opEquals(Lhs, Rhs)(Lhs lhs, Rhs rhs)
+    if (is(Lhs == class) && is(Rhs == class))
+{
+    // If aliased to the same object or both null => equal
+    if (lhs is rhs) return true;
+
+    // If either is null => non-equal
+    if (lhs is null || rhs is null) return false;
+
+    // If same exact type => one call to method opEquals
+    if (typeid(lhs) is typeid(rhs) || typeid(lhs).opEquals(typeid(rhs)))
+        return lhs.opEquals(rhs);
+
+    static if (is(Lhs == const) || is(Rhs == const))
+    {
+        // const   == const
+        // mutable == const
+        // const   == mutable
+
+        // General case => symmetric calls to method opEquals
+        return lhs.opEquals(rhs) && rhs.opEquals(lhs);
+    }
+    else
+    {
+        // mutable == mutable
+
+        // #1 require that parameter type is mutable Object version ?
+        // == calling
+        //          ( Lhs.opEquals(Object) or Lhs.opEquals(const Object) const )
+        //      and ( Rhs.opEquals(Object) or Rhs.opEquals(const Object) const )
+        return lhs.opEquals( cast(Object)(rhs) ) && rhs.opEquals( cast(Object)(lhs) );
+
+        // #2 or allow comparing between exact types
+        //    (Allow breaking "Loskov substitution principle")
+        // == allow calling
+        //          ( Lhs.opEquals(Rhs) or ... or Lhs.opEquals(const Object) const )
+        //      and ( Rhs.opEquals(Lhs) or ... or Rhs.opEquals(const Object) const )
+        //return lhs.opEquals( rhs ) && rhs.opEquals( lhs );
+    }
+}
 
 void setSameMutex(shared Object ownee, shared Object owner);
 

diff --git a/src/object_.d b/src/object_.d
@@ -155,7 +155,8 @@ class Object
 /************************
  * Returns true if lhs and rhs are equal.
  */
-bool opEquals(const Object lhs, const Object rhs)
+bool opEquals(Lhs, Rhs)(Lhs lhs, Rhs rhs)
+    if (is(Lhs == class) && is(Rhs == class))
 {
     // If aliased to the same object or both null => equal
     if (lhs is rhs) return true;
@@ -167,8 +168,32 @@ bool opEquals(const Object lhs, const Object rhs)
     if (typeid(lhs) is typeid(rhs) || typeid(lhs).opEquals(typeid(rhs)))
         return lhs.opEquals(rhs);
 
-    // General case => symmetric calls to method opEquals
-    return lhs.opEquals(rhs) && rhs.opEquals(lhs);
+    static if (is(Lhs == const) || is(Rhs == const))
+    {
+        // const   == const
+        // mutable == const
+        // const   == mutable
+
+        // General case => symmetric calls to method opEquals
+        return lhs.opEquals(rhs) && rhs.opEquals(lhs);
+    }
+    else
+    {
+        // mutable == mutable
+
+        // #1 require that parameter type is mutable Object version ?
+        // == calling
+        //          ( Lhs.opEquals(Object) or Lhs.opEquals(const Object) const )
+        //      and ( Rhs.opEquals(Object) or Rhs.opEquals(const Object) const )
+        return lhs.opEquals( cast(Object)(rhs) ) && rhs.opEquals( cast(Object)(lhs) );
+
+        // #2 or allow comparing between exact types
+        //    (Allow breaking "Loskov substitution principle")
+        // == allow calling
+        //          ( Lhs.opEquals(Rhs) or ... or Lhs.opEquals(const Object) const )
+        //      and ( Rhs.opEquals(Lhs) or ... or Rhs.opEquals(const Object) const )
+        //return lhs.opEquals( rhs ) && rhs.opEquals( lhs );
+    }
 }
 
 /**