Work in progress: changes to interpretation

frog/value.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 
 /**
  * Represents a meta-value for code generation.
  */
 class Value {
   /** The inferred (i.e. most precise) [Type] of the [Value]. */
@@ skipping 48 matching lines @@
 
     var ret = x._tryUnion(y);
     if (ret != null) return ret;
 
     // TODO(jmesserly): might want to call a _tryUnionReversed here.
     ret = y._tryUnion(x);
     if (ret != null) return ret;
 
     // TODO(jmesserly): should use something like UnionValue and track the
     // precise set of types. For now we find the Type.union.
+    var t = Type.union(x.type, y.type);
+    if (t == x.type) return x;
+    if (t == y.type) return y;
 
     // TODO(jmesserly): What to do about code? Right now, we're intentionally
     // throwing it away because they aren't used in the current flow-insensitive
     // inference.
-    return new Value(Type.union(x.type, y.type), null, null);
+    return new Value(t, null, null);
   }
 
   Value _tryUnion(Value right) => null;
 
   // TODO(jimhug): remove once type system works better.
   setField(Member field, Value value, [bool duringInit = false]) { }
 
   // Nothing to do in general?
   validateInitialized(SourceSpan span) { }
 
@@ skipping 1383 matching lines @@
     }
     return super.unop(kind, context, node);
   }
   Value binop(int kind, var other, MethodGenerator context, var node) {
     if (value != null) {
       return replaceValue(value.binop(kind, _unwrap(other), context, node));
     }
     return super.binop(kind, other, context, node);
   }
 }
+