num implements Comparable and Hashable.

lib/compiler/implementation/ssa/optimize.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.
 
 interface OptimizationPhase {
   String get name;
   void visitGraph(HGraph graph);
 }
 
 class SsaOptimizerTask extends CompilerTask {
@@ skipping 494 matching lines @@
     Element element = type.element;
     if (element.kind === ElementKind.TYPE_VARIABLE) {
       compiler.unimplemented("visitIs for type variables");
     }
 
     HType expressionType = types[node.expression];
     if (element === compiler.objectClass
         || element === compiler.dynamicClass) {
       return graph.addConstantBool(true, constantSystem);
     } else if (expressionType.isInteger()) {
-      if (element === compiler.intClass || element === compiler.numClass) {
+      if (element === compiler.intClass
+          || element === compiler.numClass
+          || Elements.isNumberOrStringSupertype(element, compiler)) {
         return graph.addConstantBool(true, constantSystem);
       } else if (element === compiler.doubleClass) {
         // We let the JS semantics decide for that check. Currently
         // the code we emit will always return true.
         return node;
       } else {
         return graph.addConstantBool(false, constantSystem);
       }
     } else if (expressionType.isDouble()) {
-      if (element === compiler.doubleClass || element === compiler.numClass) {
+      if (element === compiler.doubleClass
+          || element === compiler.numClass
+          || Elements.isNumberOrStringSupertype(element, compiler)) {
         return graph.addConstantBool(true, constantSystem);
       } else if (element === compiler.intClass) {
         // We let the JS semantics decide for that check. Currently
         // the code we emit will return true for a double that can be
         // represented as a 31-bit integer and for -0.0.
         return node;
       } else {
         return graph.addConstantBool(false, constantSystem);
       }
     } else if (expressionType.isNumber()) {
       if (element === compiler.numClass) {
         return graph.addConstantBool(true, constantSystem);
       }
       // We cannot just return false, because the expression may be of
       // type int or double.
     } else if (expressionType.isString()) {
       if (element === compiler.stringClass
-               || Elements.isStringSupertype(element, compiler)) {
+               || Elements.isStringOnlySupertype(element, compiler)
+               || Elements.isNumberOrStringSupertype(element, compiler)) {
         return graph.addConstantBool(true, constantSystem);
       } else {
         return graph.addConstantBool(false, constantSystem);
       }
     } else if (expressionType.isArray()) {
       if (element === compiler.listClass
           || Elements.isListSupertype(element, compiler)) {
         return graph.addConstantBool(true, constantSystem);
       } else {
         return graph.addConstantBool(false, constantSystem);
@@ skipping 791 matching lines @@
       // this type for the field is still a strong signal
       // indicating the expected type of the field.
       types[field] = type;
     } else {
       // If there are no invoked setters we know the type of
       // this field for sure.
       field.guaranteedType = type;
     }
   }
 }