--- a/sema/DType.d	Mon Apr 28 21:47:01 2008 +0200
+++ b/sema/DType.d	Mon Apr 28 21:51:39 2008 +0200
@@ -55,6 +55,12 @@
     Location getLoc() { return loc; }
     int byteSize() { return 0; }
 
+    /**
+      Can this type legally be converted to that type with no casts?
+      True for short -> int etc.
+     */
+    bool hasImplicitConversionTo(DType that) { return false; }
+
     static DInteger
         Bool,
         Byte, UByte, Short, UShort,
@@ -92,6 +98,13 @@
 
     override int byteSize() { return bits / 8; }
 
+    override bool hasImplicitConversionTo(DType that)
+    {
+        if (auto o = cast(DInteger)that)
+            return this.bits >= o.bits;
+        return false;
+    }
+
     int bits;
     bool unsigned;
 }
@@ -123,7 +136,9 @@
 
     DType typeOf(char[] name)
     {
-        return members[name].type;
+        if (auto res = name in members)
+            return res.type;
+        return null;
     }
 
     DStructMember[char[]] members;