Fix summary handling of unresolved imports, exports, and parts.

pkg/analyzer/lib/src/dart/resolver/scope.dart

 // Copyright (c) 2014, 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.src.dart.resolver.scope;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 434 matching lines @@
             ImportElement importElement) =>
         importElement.combinators.where((NamespaceCombinator combinator) =>
             combinator is ShowElementCombinator);
     if (node is PrefixedIdentifier) {
       String prefix = node.prefix.name;
       String name = node.identifier.name;
       List<ImportElement> imports = _definingLibrary.imports;
       int count = imports.length;
       for (int i = 0; i < count; i++) {
         ImportElement importElement = imports[i];
-        if (importElement.prefix?.name == prefix && !importElement.uriExists) {
+        if (importElement.prefix?.name == prefix &&
+            importElement.importedLibrary?.isSynthetic != false) {
           Iterable<NamespaceCombinator> showCombinators =
               getShowCombinators(importElement);
           if (showCombinators.isEmpty) {
             return true;
           }
           for (ShowElementCombinator combinator in showCombinators) {
             if (combinator.shownNames.contains(name)) {
               return true;
             }
           }
         }
       }
     } else if (node is SimpleIdentifier) {
       String name = node.name;
       List<ImportElement> imports = _definingLibrary.imports;
       int count = imports.length;
       for (int i = 0; i < count; i++) {
         ImportElement importElement = imports[i];
-        if (importElement.prefix == null && !importElement.uriExists) {
+        if (importElement.prefix == null &&
+            importElement.importedLibrary?.isSynthetic != false) {
           for (ShowElementCombinator combinator
               in getShowCombinators(importElement)) {
             if (combinator.shownNames.contains(name)) {
               return true;
             }
           }
         }
       }
     }
     return false;
@@ skipping 783 matching lines @@
 
   /**
    * Define the type parameters declared by the [classElement].
    */
   void _defineTypeParameters(ClassElement classElement) {
     for (TypeParameterElement typeParameter in classElement.typeParameters) {
       define(typeParameter);
     }
   }
 }