During linking, resolve initializers of constant variables with flow analysis.

Change-Id: I6189cdf86f0e285883da769ceb0b36d6ee85588c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/151086
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

Author: scheglov

pkg/analyzer/lib/src/summary2/top_level_inference.dart

@@ -99,6 +99,7 @@ class ConstantInitializersResolver {
             InferenceContext.setType(variable.initializer, typeNode.type);
             return variable.initializer;
           },
+          isTopLevelVariableInitializer: true,
         );
       }
     }

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

@@ -3996,6 +3996,24 @@ const Symbol vSymbol = #aaa.bbb.ccc;
 ''');
   }
 
+  test_const_topLevel_nullSafe_nullAware_propertyAccess() async {
+    featureSet = enableNnbd;
+    var library = await checkLibrary(r'''
+const String? a = '';
+
+const List<int?> b = [
+  a?.length,
+];
+''');
+    // TODO(scheglov) include fully resolved AST, when types with suffixes
+    checkElementText(library, r'''
+const String a = '';
+const List<int> b = [
+        a/*location: test.dart;a?*/.
+        length/*location: dart:core;String;length?*/];
+''');
+  }
+
   test_const_topLevel_parenthesis() async {
     var library = await checkLibrary(r'''
 const int v1 = (1 + 2) * 3;