Start implementing checked mode and tools support for using it.

lib/compiler/implementation/ssa/optimize.dart

 // Copyright (c) 2011, 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 112 matching lines @@
   HInstruction visitInstruction(HInstruction node) {
     return node;
   }
 
   HInstruction visitBoolify(HBoolify node) {
     List<HInstruction> inputs = node.inputs;
     assert(inputs.length == 1);
     HInstruction input = inputs[0];
     if (input.isBoolean()) return input;
     // All values !== true are boolified to false.
-    if (input.propagatedType.isUseful()) {
+    Type type = input.propagatedType.computeType(compiler);
+    if (type !== null && type.element !== compiler.boolClass) {
       return graph.addConstantBool(false);
     }
     return node;
   }
 
   HInstruction visitNot(HNot node) {
     List<HInstruction> inputs = node.inputs;
     assert(inputs.length == 1);
     HInstruction input = inputs[0];
     if (input is HConstant) {
@@ skipping 286 matching lines @@
       } else if (right.isConstantNull()) {
         return graph.addConstantBool(false);
       } else {
         // We can just emit an identity check because the type does
         // not implement operator=.
         return foldBuiltinEqualsCheck(node);
       }
     }
 
     if (right.isConstantNull()) {
-      if (left.propagatedType.isUseful()) {
+      if (!left.propagatedType.canBeNull()) {

[floitsch, 2012/05/07 09:50:07]

I would prefer switching to the new semantics in a separate CL.

[ngeoffray, 2012/05/07 13:15:42]

This should have been if (leg.propagatedType.isPrimitive()) ...

         return graph.addConstantBool(false);
       } else {
         // TODO(floitsch): cache interceptors.
         Interceptors interceptors = compiler.builder.interceptors;
         Element equalsElement = interceptors.getEqualsInterceptor();
         // If we have a different element than [equalsElement], we
         // don't need to optimize this instruction to use another
         // element: we know the element is either eqNull or eqNullB.
         if (node.element === equalsElement) {
           Element targetElement = interceptors.getEqualsNullInterceptor();
@@ skipping 74 matching lines @@
       }
     } else if (expressionType.isArray()) {
       if (element === compiler.listClass
           || Elements.isListSupertype(element, compiler)) {
         return graph.addConstantBool(true);
       } else {
         return graph.addConstantBool(false);
       }
     // TODO(karlklose): remove the hasTypeArguments check.
     } else if (expressionType.isUseful()
+               && !expressionType.canBeNull()

[floitsch, 2012/05/07 09:50:07]

you could move that check into the 'true' section.
if the is-check would be false, then 'null' can't change that.

[ngeoffray, 2012/05/07 13:15:42]

Done.

                && !compiler.universe.rti.hasTypeArguments(type)) {
       Type receiverType = expressionType.computeType(compiler);
       if (receiverType !== null) {
         if (compiler.types.isSubtype(receiverType, type)) {
           return graph.addConstantBool(true);
         } else if (expressionType.isExact()) {
           return graph.addConstantBool(false);
         }
       }
     }
@@ skipping 502 matching lines @@
           newInput = new HTypeConversion(convertedType, input);
           dominator.addBefore(dominator.first, newInput);
         }
         user.changeUse(input, newInput);
       }
     }
   }
 
   void visitIs(HIs instruction) {
     HInstruction input = instruction.expression;
+    HType convertedType =
+        new HType.fromBoundedType(instruction.typeExpression, compiler);
+    if (convertedType === null) return;
+
     List<HInstruction> ifUsers = <HInstruction>[];
     List<HInstruction> notIfUsers = <HInstruction>[];
 
     for (HInstruction user in instruction.usedBy) {
       if (user is HIf) {
         ifUsers.add(user);
       } else if (user is HNot) {
         for (HInstruction notUser in user.usedBy) {
           if (notUser is HIf) notIfUsers.add(notUser);
         }
       }
     }
 
     if (ifUsers.isEmpty() && notIfUsers.isEmpty()) return;
 
-    HType convertedType =
-        new HType.fromBoundedType(instruction.typeExpression, compiler);
-
     for (HIf ifUser in ifUsers) {
       changeUsesDominatedBy(ifUser.thenBlock, input, convertedType);
       // TODO(ngeoffray): Also change uses for the else block on a HType
       // that knows it is not of a specific Type.
     }
 
     for (HIf ifUser in notIfUsers) {
       if (ifUser.hasElse) {
         changeUsesDominatedBy(ifUser.elseBlock, input, convertedType);
       } else if (ifUser.joinBlock.predecessors.length == 1) {
         // If the join block has only one predecessor, then we know
         // the if block terminates. So any use of the instruction
         // after the join block should be changed to the new
         // instruction.
         changeUsesDominatedBy(ifUser.joinBlock, input, convertedType);
       }
       // TODO(ngeoffray): Also change uses for the then block on a HType
       // that knows it is not of a specific Type.
     }
   }
 }