diff --git a/pkg/analysis_server/lib/src/lsp/handlers/code_actions/plugins.dart b/pkg/analysis_server/lib/src/lsp/handlers/code_actions/plugins.dart
index ca3f9fd28426..3c392a0f9568 100644
--- a/pkg/analysis_server/lib/src/lsp/handlers/code_actions/plugins.dart
+++ b/pkg/analysis_server/lib/src/lsp/handlers/code_actions/plugins.dart
@@ -61,7 +61,7 @@ class PluginCodeActionsProducer extends AbstractCodeActionsProducer {
         .map((response) => plugin.EditGetFixesResult.fromResponse(response))
         .expand((response) => response.fixes)
         .map(_convertFixes)
-        .flattenedToList;
+        .flattenedToList2;
   }
 
   @override
diff --git a/pkg/analysis_server/lib/src/lsp/handlers/handler_semantic_tokens.dart b/pkg/analysis_server/lib/src/lsp/handlers/handler_semantic_tokens.dart
index e2f0acd1bbfe..058205332313 100644
--- a/pkg/analysis_server/lib/src/lsp/handlers/handler_semantic_tokens.dart
+++ b/pkg/analysis_server/lib/src/lsp/handlers/handler_semantic_tokens.dart
@@ -66,7 +66,7 @@ abstract class AbstractSemanticTokensHandler<T>
 
       return toSourceRangeNullable(lineInfo, range).mapResult((range) async {
         final serverTokens = await getServerResult(path, range);
-        final pluginHighlightRegions = getPluginResults(path).flattenedToList;
+        final pluginHighlightRegions = getPluginResults(path).flattenedToList2;
 
         if (token.isCancellationRequested) {
           return cancelled();
diff --git a/pkg/analysis_server/lib/src/lsp/mapping.dart b/pkg/analysis_server/lib/src/lsp/mapping.dart
index 74670340b420..fe8551099a31 100644
--- a/pkg/analysis_server/lib/src/lsp/mapping.dart
+++ b/pkg/analysis_server/lib/src/lsp/mapping.dart
@@ -1166,7 +1166,7 @@ List<lsp.DocumentHighlight> toHighlights(
       .map((occurrence) => occurrence.offsets.map((offset) =>
           lsp.DocumentHighlight(
               range: toRange(lineInfo, offset, occurrence.length))))
-      .flattenedToSet
+      .flattenedToSet2
       .toList();
 }
 
diff --git a/pkg/analysis_server/lib/src/lsp/semantic_tokens/legend.dart b/pkg/analysis_server/lib/src/lsp/semantic_tokens/legend.dart
index 366015c5df3d..0962692af028 100644
--- a/pkg/analysis_server/lib/src/lsp/semantic_tokens/legend.dart
+++ b/pkg/analysis_server/lib/src/lsp/semantic_tokens/legend.dart
@@ -35,7 +35,7 @@ class SemanticTokenLegendLookup {
             .followedBy(CustomSemanticTokenTypes.values))
         .toList();
     _usedTokenModifiers = Set.of(highlightRegionTokenModifiers
-            .values.flattenedToList
+            .values.flattenedToList2
             .followedBy(CustomSemanticTokenModifiers.values))
         .toList();
 
diff --git a/pkg/analysis_server/lib/src/operation/operation_analysis.dart b/pkg/analysis_server/lib/src/operation/operation_analysis.dart
index 10cffda5d5aa..c483cae95f2e 100644
--- a/pkg/analysis_server/lib/src/operation/operation_analysis.dart
+++ b/pkg/analysis_server/lib/src/operation/operation_analysis.dart
@@ -43,7 +43,7 @@ void sendAnalysisNotificationAnalyzedFiles(LegacyAnalysisServer server) {
   _sendNotification(server, () {
     var analyzedFiles = server.driverMap.values
         .map((driver) => driver.knownFiles)
-        .flattenedToSet;
+        .flattenedToSet2;
 
     // Exclude *.yaml files because IDEA Dart plugin attempts to index
     // all the files in folders which contain analyzed files.
diff --git a/pkg/analysis_server/lib/src/services/correction/fix/data_driven/transform_set_parser.dart b/pkg/analysis_server/lib/src/services/correction/fix/data_driven/transform_set_parser.dart
index 8dfa0f36ff8b..04ec1342e21b 100644
--- a/pkg/analysis_server/lib/src/services/correction/fix/data_driven/transform_set_parser.dart
+++ b/pkg/analysis_server/lib/src/services/correction/fix/data_driven/transform_set_parser.dart
@@ -352,7 +352,7 @@ class TransformSetParser {
     if (firstEntry == null) {
       if (required) {
         var validKeysList =
-            translators.keys.flattenedToList.quotedAndCommaSeparatedWithOr;
+            translators.keys.flattenedToList2.quotedAndCommaSeparatedWithOr;
         _reportError(TransformSetErrorCode.missingOneOfMultipleKeys, errorNode,
             [validKeysList]);
       }
diff --git a/pkg/analysis_server/lib/src/utilities/import_analyzer.dart b/pkg/analysis_server/lib/src/utilities/import_analyzer.dart
index 90ecb647af13..84acdc36c052 100644
--- a/pkg/analysis_server/lib/src/utilities/import_analyzer.dart
+++ b/pkg/analysis_server/lib/src/utilities/import_analyzer.dart
@@ -299,7 +299,7 @@ class _ReferenceFinder extends RecursiveAstVisitor<void> {
     // Extensions can be used without a prefix, so we can use any import that
     // brings in the extension.
     if (import == null && prefix == null && element is ExtensionElement) {
-      import = _importsByPrefix.values.flattenedToList
+      import = _importsByPrefix.values.flattenedToList2
           .where((import) =>
               // Because we don't know what prefix we're looking for (any is
               // allowed), use the imports own prefix when checking for the
diff --git a/pkg/analyzer/lib/src/dart/analysis/driver.dart b/pkg/analyzer/lib/src/dart/analysis/driver.dart
index f22ea8b9b4bb..d010d37e757b 100644
--- a/pkg/analyzer/lib/src/dart/analysis/driver.dart
+++ b/pkg/analyzer/lib/src/dart/analysis/driver.dart
@@ -2526,7 +2526,7 @@ class _DiscoverAvailableFilesTask {
       // Discover files in package/lib folders.
       var packageMap = driver._sourceFactory.packageMap;
       if (packageMap != null) {
-        folderIterator = packageMap.values.flattenedToList.iterator;
+        folderIterator = packageMap.values.flattenedToList2.iterator;
       } else {
         folderIterator = <Folder>[].iterator;
       }
diff --git a/pkg/analyzer/lib/src/dart/analysis/library_graph.dart b/pkg/analyzer/lib/src/dart/analysis/library_graph.dart
index c1113f8fc68d..8ac71dd177a1 100644
--- a/pkg/analyzer/lib/src/dart/analysis/library_graph.dart
+++ b/pkg/analyzer/lib/src/dart/analysis/library_graph.dart
@@ -149,7 +149,7 @@ class _LibraryNode extends graph.Node<_LibraryNode> {
                   .whereType<LibraryExportWithFile>()
                   .map((export) => export.exportedLibrary),
             ])
-        .flattenedToList
+        .flattenedToList2
         .whereNotNull()
         .toSet();
 
diff --git a/pkg/analyzer/lib/src/dart/element/generic_inferrer.dart b/pkg/analyzer/lib/src/dart/element/generic_inferrer.dart
index 414f0113cc1d..143eb7465b7d 100644
--- a/pkg/analyzer/lib/src/dart/element/generic_inferrer.dart
+++ b/pkg/analyzer/lib/src/dart/element/generic_inferrer.dart
@@ -497,7 +497,7 @@ class GenericInferrer {
         .values
         .where((l) =>
             l.every((c) => c.isSatisfiedBy(_typeSystem, inferred)) == expected)
-        .flattenedToList;
+        .flattenedToList2;
 
     String unsatisfied = _formatConstraints(isSatisfied(false));
     String satisfied = _formatConstraints(isSatisfied(true));
diff --git a/pkg/analyzer/lib/src/fasta/ast_builder.dart b/pkg/analyzer/lib/src/fasta/ast_builder.dart
index e5bffb313f84..73ffec2ae051 100644
--- a/pkg/analyzer/lib/src/fasta/ast_builder.dart
+++ b/pkg/analyzer/lib/src/fasta/ast_builder.dart
@@ -3080,7 +3080,7 @@ class AstBuilder extends StackListener {
     debugEvent("SwitchBlock");
 
     var membersList = popTypedList2<List<SwitchMemberImpl>>(caseCount);
-    var members = membersList.flattenedToList;
+    var members = membersList.flattenedToList2;
 
     Set<String> labels = <String>{};
     for (var member in members) {
diff --git a/pkg/analyzer/lib/src/summary2/library_builder.dart b/pkg/analyzer/lib/src/summary2/library_builder.dart
index 9783e88ccad5..8ef11d1f78d2 100644
--- a/pkg/analyzer/lib/src/summary2/library_builder.dart
+++ b/pkg/analyzer/lib/src/summary2/library_builder.dart
@@ -460,7 +460,7 @@ class LibraryBuilder {
     }
 
     final augmentationCode = macroApplier.buildAugmentationLibraryCode(
-      _macroResults.flattenedToList,
+      _macroResults.flattenedToList2,
     );
     if (augmentationCode == null) {
       return;
diff --git a/pkg/analyzer/lib/src/utilities/extensions/collection.dart b/pkg/analyzer/lib/src/utilities/extensions/collection.dart
index 256834a29933..81c29b907e20 100644
--- a/pkg/analyzer/lib/src/utilities/extensions/collection.dart
+++ b/pkg/analyzer/lib/src/utilities/extensions/collection.dart
@@ -27,14 +27,14 @@ extension IterableIterableExtension<T> on Iterable<Iterable<T>> {
   /// At the moment of writing, this method is `2.75` times faster than
   /// `expand((e) => e)`, and `3.5` faster than `flattened` from
   /// `package:collection`.
-  List<T> get flattenedToList {
+  List<T> get flattenedToList2 {
     return [
       for (final elements in this) ...elements,
     ];
   }
 
   /// Elements of each iterable in this iterable.
-  Set<T> get flattenedToSet {
+  Set<T> get flattenedToSet2 {
     return {
       for (final elements in this) ...elements,
     };
diff --git a/pkg/analyzer/test/src/dart/element/inheritance_manager3_test.dart b/pkg/analyzer/test/src/dart/element/inheritance_manager3_test.dart
index d6f7cc4d9584..4e4333bd95a3 100644
--- a/pkg/analyzer/test/src/dart/element/inheritance_manager3_test.dart
+++ b/pkg/analyzer/test/src/dart/element/inheritance_manager3_test.dart
@@ -3023,7 +3023,7 @@ class _InterfacePrinter {
     String name,
     Map<Name, List<ExecutableElement>> map,
   ) {
-    final isEmpty = map.values.flattenedToList.where((element) {
+    final isEmpty = map.values.flattenedToList2.where((element) {
       if (_configuration.withObjectMembers) return true;
       return !element.isObjectMember;
     }).isEmpty;
diff --git a/pkg/analyzer/test/src/utilities/extensions/collection_test.dart b/pkg/analyzer/test/src/utilities/extensions/collection_test.dart
index 9d824a36454a..ff867230e3c3 100644
--- a/pkg/analyzer/test/src/utilities/extensions/collection_test.dart
+++ b/pkg/analyzer/test/src/utilities/extensions/collection_test.dart
@@ -30,7 +30,7 @@ class IterableIterableExtensionTest {
         [0],
         [1, 2],
         [3, 3]
-      ].flattenedToList,
+      ].flattenedToList2,
       [0, 1, 2, 3, 3],
     );
   }
@@ -41,7 +41,7 @@ class IterableIterableExtensionTest {
         [0, 0],
         [1, 2, 1],
         [3, 3]
-      ].flattenedToSet,
+      ].flattenedToSet2,
       {0, 1, 2, 3},
     );
   }