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

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 603 matching lines @@
           break;
       }
     }
     return new HFieldGet(field, node.inputs[0]);
   }
 
   HInstruction visitInvokeDynamicSetter(HInvokeDynamicSetter node) {
     Element field =
         findConcreteFieldForDynamicAccess(node.receiver, node.selector);
     if (field === null) return node;
-    return new HFieldSet(field, node.inputs[0], node.inputs[1]);
+    HInstruction value = node.inputs[1];
+    if (compiler.enableTypeAssertions) {
+      HInstruction other = value.convertType(
+          compiler, field, HTypeConversion.CHECKED_MODE_CHECK);
+      if (other != value) {
+        node.block.addBefore(node, other);
+        value = other;
+      }
+    }
+    return new HFieldSet(field, node.inputs[0], value);
   }
 
   HInstruction visitStringConcat(HStringConcat node) {
     DartString folded = const LiteralDartString("");
     for (int i = 0; i < node.inputs.length; i++) {
       HInstruction part = node.inputs[i];
       if (!part.isConstant()) return node;
       HConstant constant = part;
       if (!constant.constant.isPrimitive()) return node;
       PrimitiveConstant primitive = constant.constant;
@@ skipping 695 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;
     }
   }
 }