Allow 'extract index' in top-level inference.

pkg/analyzer/test/src/summary/top_level_inference_test.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.
 
 import 'dart:async';
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
@@ skipping 109 matching lines @@
 
   test_initializer_equality() async {
     var content = r'''
 var a = 1;
 var t1 = ((a = 1) == 0) == ((a = 2) == 0);
 var t2 = ((a = 1) == 0) != ((a = 2) == 0);
 ''';
     await checkFile(content);
   }
 
+  test_initializer_extractIndex() async {
+    var content = r'''
+var a = /*info:INFERRED_TYPE_LITERAL*/[0, 1.2];
+var b0 = a[0];
+var b1 = a[1];
+''';
+    await checkFile(content);
+  }
+
   test_initializer_functionLiteral_blockBody() async {
     var content = r'''
 var t = /*error:TOP_LEVEL_FUNCTION_LITERAL_BLOCK*/
         /*info:INFERRED_TYPE_CLOSURE*/
         (int p) {};
 ''';
     await checkFile(content);
   }
 
   test_initializer_functionLiteral_expressionBody() async {
@@ skipping 724 matching lines @@
 class C {
   static D get d {}
 }
 class D {
   int i;
 }
 dynamic x/*error: instanceGetter*/;
 ''');
   }
 
+  test_initializer_extractIndex() async {
+    var library = await _encodeDecodeLibrary(r'''
+var a = [0, 1.2];
+var b0 = a[0];
+var b1 = a[1];
+''');
+    checkElementText(
+        library,
+        r'''
+List<num> a;
+num b0;
+num b1;
+''');
+  }
+
   test_initializer_functionExpression() async {
     var library = await _encodeDecodeLibrary(r'''
 import 'dart:async';
 var vFuture = new Future<int>(42);
 var v_noParameters_inferredReturnType = () => 42;
 var v_hasParameter_withType_inferredReturnType = (String a) => 42;
 var v_hasParameter_withType_returnParameter = (String a) => a;
 var v_async_returnValue = () async => 42;
 var v_async_returnFuture = () async => vFuture;
 ''');
@@ skipping 1891 matching lines @@
 
   Future<LibraryElement> _encodeDecodeLibrary(String text) async {
     String path = _p('/test.dart');
     provider.newFile(path, text);
     UnitElementResult result = await driver.getUnitElement(path);
     return result.element.library;
   }
 
   String _p(String path) => provider.convertPath(path);
 }