--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dmd/expression/util/arrayTypeCompatible.d	Sat Oct 24 08:42:06 2009 +0400
@@ -0,0 +1,34 @@
+module dmd.expression.util.arrayTypeCompatible;
+
+import dmd.Loc;
+import dmd.Type;
+import dmd.TY;
+import dmd.MATCH;
+import dmd.Util;
+
+/***********************************
+ * See if both types are arrays that can be compared
+ * for equality. Return !=0 if so.
+ * If they are arrays, but incompatible, issue error.
+ * This is to enable comparing things like an immutable
+ * array with a mutable one.
+ */
+bool arrayTypeCompatible(Loc loc, Type t1, Type t2)
+{
+    t1 = t1.toBasetype();
+    t2 = t2.toBasetype();
+
+    if ((t1.ty == TY.Tarray || t1.ty == TY.Tsarray || t1.ty == TY.Tpointer) && (t2.ty == TY.Tarray || t2.ty == TY.Tsarray || t2.ty == TY.Tpointer))
+	{
+		if (t1.nextOf().implicitConvTo(t2.nextOf()) < MATCH.MATCHconst && 
+			t2.nextOf().implicitConvTo(t1.nextOf()) < MATCH.MATCHconst &&
+			(t1.nextOf().ty != TY.Tvoid && t2.nextOf().ty != TY.Tvoid))
+		{
+			error(loc, "array equality comparison type mismatch, %s vs %s", t1.toChars(), t2.toChars());
+		}
+		
+		return true;
+    }
+
+    return false;
+}
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