No more warnings for duplicate unnamed lib imports.

pkg/analyzer/test/generated/non_error_resolver_test.dart

Index: pkg/analyzer/test/generated/non_error_resolver_test.dart
diff --git a/pkg/analyzer/test/generated/non_error_resolver_test.dart b/pkg/analyzer/test/generated/non_error_resolver_test.dart
index f4eea16a240f4ce2cc47e75f462ea6b125c46119..476bc198e73e5f90d9d549e7fb27177ee2c094c2 100644
--- a/pkg/analyzer/test/generated/non_error_resolver_test.dart
+++ b/pkg/analyzer/test/generated/non_error_resolver_test.dart
@@ -1450,6 +1450,18 @@ main() {
     verify([source]);
   }
 
+  void test_exportDuplicatedLibraryUnnamed() {
+    Source source = addSource(r'''
+library test;
+export 'lib1.dart';
+export 'lib2.dart';''');
+    addNamedSource("/lib1.dart", "");
+    addNamedSource("/lib2.dart", "");
+    computeLibrarySourceErrors(source);
+    assertNoErrors(source);
+    verify([source]);
+  }
+
   void test_exportOfNonLibrary_libraryDeclared() {
     Source source = addSource(r'''
 library L;
@@ -1968,6 +1980,22 @@ import 'lib.dart';''');
     verify([source]);
   }
 
+  void test_importDuplicatedLibraryUnnamed() {
+    Source source = addSource(r'''
+library test;
+import 'lib1.dart';
+import 'lib2.dart';''');
+    addNamedSource("/lib1.dart", "");
+    addNamedSource("/lib2.dart", "");
+    computeLibrarySourceErrors(source);
+    assertErrors(source, [
+      // No warning on duplicate import (https://github.com/dart-lang/sdk/issues/24156)
+      HintCode.UNUSED_IMPORT,
+      HintCode.UNUSED_IMPORT
+    ]);
+    verify([source]);
+  }
+
   void test_importOfNonLibrary_libraryDeclared() {
     Source source = addSource(r'''
 library lib;