Add type inference for complex assignments whose LHS is an index expression.

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

 // Copyright (c) 2016, 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.
 
 library fasta.body_builder;
 
 import '../fasta_codes.dart'
     show FastaMessage, codeExpectedButGot, codeExpectedFunctionBody;
 
 import '../parser/parser.dart' show FormalParameterType, MemberKind, optional;
@@ skipping 729 matching lines @@
     push(new KernelLogicalExpression(receiver, token.stringValue, argument));
   }
 
   /// Handle `a ?? b`.
   void doIfNull(Token token) {
     Expression b = popForValue();
     Expression a = popForValue();
     VariableDeclaration variable = new VariableDeclaration.forValue(a);
     push(makeLet(
         variable,
-        new ConditionalExpression(buildIsNull(new VariableGet(variable)), b,
-            new VariableGet(variable), const DynamicType())));
+        new KernelConditionalExpression(buildIsNull(new VariableGet(variable)),
+            b, new VariableGet(variable))));
   }
 
   /// Handle `a?.b(...)`.
   void doIfNotNull(Token token) {
     IncompleteSend send = pop();
     push(send.withReceiver(pop(), token.charOffset, isNullAware: true));
   }
 
   void doDotOrCascadeExpression(Token token) {
     // TODO(ahe): Handle null-aware.
@@ skipping 2090 matching lines @@
       {bool isConstantExpression: false,
       bool isNullAware: false,
       bool isImplicitCall: false}) {
     if (constantExpressionRequired && !isConstantExpression) {
       return buildCompileTimeError("Not a constant expression.", offset);
     }
     if (isNullAware) {
       VariableDeclaration variable = new VariableDeclaration.forValue(receiver);
       return makeLet(
           variable,
-          new ConditionalExpression(
+          new KernelConditionalExpression(
               buildIsNull(new VariableGet(variable)),
               new NullLiteral(),
               new MethodInvocation(new VariableGet(variable), name, arguments)
-                ..fileOffset = offset,
-              const DynamicType()));
+                ..fileOffset = offset));
     } else {
       return new KernelMethodInvocation(receiver, name, arguments,
           isImplicitCall: isImplicitCall)
         ..fileOffset = offset;
     }
   }
 
   @override
   void addCompileTimeErrorFromMessage(FastaMessage message) {
     library.addCompileTimeError(message.charOffset, message.message,
@@ skipping 452 matching lines @@
     if (starToken == null) {
       return AsyncMarker.Async;
     } else {
       assert(identical(starToken.stringValue, "*"));
       return AsyncMarker.AsyncStar;
     }
   } else {
     return internalError("Unknown async modifier: $asyncToken");
   }
 }