infer null from context, this avoids bottom being introduced

pkg/analyzer/test/src/summary/summary_common.dart

 // Copyright (c) 2015, 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 analyzer.test.src.summary.summary_common;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/scanner/reader.dart';
@@ skipping 8428 matching lines @@
       return;
     }
     UnlinkedClass cls = serializeClassText('class C { final x = []; }');
     EntityRef type = getTypeRefForSlot(cls.fields[0].inferredTypeSlot);
     // Check that x has inferred type `List<dynamic>`.
     checkLinkedTypeRef(type, 'dart:core', 'dart:core', 'List',
         numTypeParameters: 1, numTypeArguments: 1);
   }
 
   test_initializer_executable_with_bottom_return_type() {
-    // The synthetic executable for `v` has type `() => Bottom`.
     UnlinkedVariable variable = serializeVariableText('int v = null;');
     expect(variable.initializer.returnType, isNull);
-    checkInferredTypeSlot(
-        variable.initializer.inferredReturnTypeSlot, null, null, '*bottom*',
-        onlyInStrongMode: false);
+    if (strongMode) {
+      // Strong mode infers a type for the closure of `() => int`.
+      checkInferredTypeSlot(variable.initializer.inferredReturnTypeSlot,
+          'dart:core', 'dart:core', 'int',
+          onlyInStrongMode: false);
+    } else {
+      // In Dart1 mode the synthetic executable for `v` has type `() => Bottom`.
+      checkInferredTypeSlot(
+          variable.initializer.inferredReturnTypeSlot, null, null, '*bottom*',
+          onlyInStrongMode: false);
+    }
   }
 
   test_initializer_executable_with_imported_return_type() {
     addNamedSource('/a.dart', 'class C { D d; } class D {}');
     // The synthetic executable for `v` has type `() => D`; `D` is defined in
     // a library that is imported.  Note: `v` is mis-typed as `int` to prevent
     // type propagation, which would complicate the test.
     UnlinkedVariable variable = serializeVariableText(
         'import "a.dart"; int v = new C().d;',
         allowErrors: true);
@@ skipping 2061 matching lines @@
 class _PrefixExpectation {
   final ReferenceKind kind;
   final String name;
   final String absoluteUri;
   final String relativeUri;
   final int numTypeParameters;
 
   _PrefixExpectation(this.kind, this.name,
       {this.absoluteUri, this.relativeUri, this.numTypeParameters: 0});
 }