Improvements for checked mode: check when intializing fields, and when assigning to fields.

lib/compiler/implementation/ssa/nodes.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 HVisitor<R> {
   R visitAdd(HAdd node);
   R visitBailoutTarget(HBailoutTarget node);
   R visitBitAnd(HBitAnd node);
   R visitBitNot(HBitNot node);
   R visitBitOr(HBitOr node);
@@ skipping 1066 matching lines @@
   bool dominates(HInstruction other) {
     if (block != other.block) return block.dominates(other.block);
 
     HInstruction current = this;
     while (current !== null) {
       if (current === other) return true;
       current = current.next;
     }
     return false;
   }
+
+
+  HInstruction convertType(Compiler compiler,
+                           Element sourceElement,
+                           int kind) {
+    DartType type = sourceElement.computeType(compiler);
+    if (type === null) return this;
+    if (type.element === compiler.dynamicClass) return this;
+    if (type.element === compiler.objectClass) return this;
+
+    // If the original can't be null, type conversion also can't produce null.
+    bool canBeNull = this.guaranteedType.canBeNull();
+    HType convertedType =
+        new HType.fromBoundedType(type, compiler, canBeNull);
+
+    // No need to convert if we know the instruction has
+    // [convertedType] as a bound.
+    if (this.guaranteedType == convertedType) {
+      return this;
+    }
+
+    return new HTypeConversion(convertedType, this, kind);
+  }
 }
 
 class HBoolify extends HInstruction {
   HBoolify(HInstruction value) : super(<HInstruction>[value]);
   void prepareGvn(HTypeMap types) {
     assert(!hasSideEffects(types));
     setUseGvn();
   }
 
   HType get guaranteedType => HType.BOOLEAN;
@@ skipping 1746 matching lines @@
   HBasicBlock get start => expression.start;
   HBasicBlock get end {
     // We don't create a switch block if there are no cases.
     assert(!statements.isEmpty());
     return statements.last().end;
   }
 
   bool accept(HStatementInformationVisitor visitor) =>
       visitor.visitSwitchInfo(this);
 }