Implement inference tests for logical operators.

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

 // Copyright (c) 2017, 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.
 
 /// This file declares a "shadow hierarchy" of concrete classes which extend
 /// the kernel class hierarchy, adding methods and fields needed by the
 /// BodyBuilder.
 ///
 /// Instances of these classes may be created using the factory methods in
 /// `ast_factory.dart`.
@@ skipping 1056 matching lines @@
       : super(left, operator, right);
 
   @override
   void _collectDependencies(KernelDependencyCollector collector) {
     // No inference dependencies.
   }
 
   @override
   DartType _inferExpression(
       KernelTypeInferrer inferrer, DartType typeContext, bool typeNeeded) {
-    // TODO(scheglov): implement.
-    return typeNeeded ? const DynamicType() : null;
+    typeNeeded = inferrer.listener.logicalExpressionEnter(this, typeContext) ||
+        typeNeeded;
+    var boolType = inferrer.coreTypes.boolClass.rawType;
+    inferrer.inferExpression(left, boolType, false);
+    inferrer.inferExpression(right, boolType, false);
+    var inferredType = typeNeeded ? boolType : null;
+    inferrer.listener.logicalExpressionExit(this, inferredType);
+    return inferredType;
   }
 }
 
 /// Shadow object for [MapLiteral].
 class KernelMapLiteral extends MapLiteral implements KernelExpression {
   final DartType _declaredKeyType;
   final DartType _declaredValueType;
 
   KernelMapLiteral(List<MapEntry> entries,
       {DartType keyType, DartType valueType, bool isConst: false})
@@ skipping 1147 matching lines @@
   }
 
   transformChildren(v) {
     return internalError("Internal error: Unsupported operation.");
   }
 
   visitChildren(v) {
     return internalError("Internal error: Unsupported operation.");
   }
 }