Always store the type of a conditional expression on the node.

lib/type_checker.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 kernel.type_checker;
 
 import 'ast.dart';
 import 'class_hierarchy.dart';
 import 'core_types.dart';
 import 'type_algebra.dart';
 import 'type_environment.dart';
@@ skipping 301 matching lines @@
   }
 
   @override
   DartType visitBoolLiteral(BoolLiteral node) {
     return environment.boolType;
   }
 
   @override
   DartType visitConditionalExpression(ConditionalExpression node) {
     checkAssignableExpression(node.condition, environment.boolType);
-    if (node.staticType == null) {
-      var thenType = visitExpression(node.then);
-      var otherwiseType = visitExpression(node.otherwise);
-      if (thenType is BottomType) return otherwiseType;
-      if (otherwiseType is BottomType) return thenType;
-      return const DynamicType();
-    } else {
-      checkAssignableExpression(node.then, node.staticType);
-      checkAssignableExpression(node.otherwise, node.staticType);
-      return node.staticType;
-    }
+    checkAssignableExpression(node.then, node.staticType);
+    checkAssignableExpression(node.otherwise, node.staticType);
+    return node.staticType;
   }
 
   @override
   DartType visitConstructorInvocation(ConstructorInvocation node) {
     Constructor target = node.target;
     Arguments arguments = node.arguments;
     Class class_ = target.enclosingClass;
     handleCall(arguments, target.function,
         typeParameters: class_.typeParameters);
     return new InterfaceType(target.enclosingClass, arguments.types);
@@ skipping 460 matching lines @@
   }
 
   @override
   visitLocalInitializer(LocalInitializer node) {
     visitVariableDeclaration(node.variable);
   }
 
   @override
   visitInvalidInitializer(InvalidInitializer node) {}
 }