[analysis_server] Sort types in LSP Unions consistently

This simplifies an upcoming change switching from parsing LSP TypeScript definitions to using a new JSON definition (where items are not all in the same order).

Change-Id: I773ce9ab174288ef5226b5f82f8ad7b8fb5f3693
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/244245
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analysis_server/lib/lsp_protocol/protocol_generated.dart

@@ -6788,12 +6788,12 @@ class CompletionItem implements ToJsonable {
     final documentationJson = json['documentation'];
     final documentation = documentationJson == null
         ? null
-        : (documentationJson is String
-            ? Either2<String, MarkupContent>.t1(documentationJson)
-            : (MarkupContent.canParse(documentationJson, nullLspJsonReporter)
-                ? Either2<String, MarkupContent>.t2(MarkupContent.fromJson(
-                    documentationJson as Map<String, Object?>))
-                : (throw '''$documentationJson was not one of (String, MarkupContent)''')));
+        : (MarkupContent.canParse(documentationJson, nullLspJsonReporter)
+            ? Either2<MarkupContent, String>.t1(MarkupContent.fromJson(
+                documentationJson as Map<String, Object?>))
+            : (documentationJson is String
+                ? Either2<MarkupContent, String>.t2(documentationJson)
+                : (throw '''$documentationJson was not one of (MarkupContent, String)''')));
     final deprecatedJson = json['deprecated'];
     final deprecated = deprecatedJson as bool?;
     final preselectJson = json['preselect'];
@@ -6815,14 +6815,14 @@ class CompletionItem implements ToJsonable {
     final textEditJson = json['textEdit'];
     final textEdit = textEditJson == null
         ? null
-        : (TextEdit.canParse(textEditJson, nullLspJsonReporter)
-            ? Either2<TextEdit, InsertReplaceEdit>.t1(
-                TextEdit.fromJson(textEditJson as Map<String, Object?>))
-            : (InsertReplaceEdit.canParse(textEditJson, nullLspJsonReporter)
-                ? Either2<TextEdit, InsertReplaceEdit>.t2(
-                    InsertReplaceEdit.fromJson(
-                        textEditJson as Map<String, Object?>))
-                : (throw '''$textEditJson was not one of (TextEdit, InsertReplaceEdit)''')));
+        : (InsertReplaceEdit.canParse(textEditJson, nullLspJsonReporter)
+            ? Either2<InsertReplaceEdit, TextEdit>.t1(
+                InsertReplaceEdit.fromJson(
+                    textEditJson as Map<String, Object?>))
+            : (TextEdit.canParse(textEditJson, nullLspJsonReporter)
+                ? Either2<InsertReplaceEdit, TextEdit>.t2(
+                    TextEdit.fromJson(textEditJson as Map<String, Object?>))
+                : (throw '''$textEditJson was not one of (InsertReplaceEdit, TextEdit)''')));
     final textEditTextJson = json['textEditText'];
     final textEditText = textEditTextJson as String?;
     final additionalTextEditsJson = json['additionalTextEdits'];
@@ -6898,7 +6898,7 @@ class CompletionItem implements ToJsonable {
   final String? detail;
 
   /// A human-readable string that represents a doc-comment.
-  final Either2<String, MarkupContent>? documentation;
+  final Either2<MarkupContent, String>? documentation;
 
   /// A string that should be used when filtering a set of completion items.
   /// When `falsy` the label is used as the filter text for this item.
@@ -6985,7 +6985,7 @@ class CompletionItem implements ToJsonable {
   /// must be a prefix of the edit's replace range, that means it must be
   /// contained and starting at the same position.
   ///  @since 3.16.0 additional type `InsertReplaceEdit`
-  final Either2<TextEdit, InsertReplaceEdit>? textEdit;
+  final Either2<InsertReplaceEdit, TextEdit>? textEdit;
 
   /// The edit text used if the completion item is part of a CompletionList and
   /// CompletionList defines an item default for the text edit range.
@@ -7127,10 +7127,10 @@ class CompletionItem implements ToJsonable {
       try {
         final documentation = obj['documentation'];
         if (documentation != null &&
-            !((documentation is String ||
-                MarkupContent.canParse(documentation, reporter)))) {
+            !((MarkupContent.canParse(documentation, reporter) ||
+                documentation is String))) {
           reporter
-              .reportError('must be of type Either2<String, MarkupContent>');
+              .reportError('must be of type Either2<MarkupContent, String>');
           return false;
         }
       } finally {
@@ -7212,10 +7212,10 @@ class CompletionItem implements ToJsonable {
       try {
         final textEdit = obj['textEdit'];
         if (textEdit != null &&
-            !((TextEdit.canParse(textEdit, reporter) ||
-                InsertReplaceEdit.canParse(textEdit, reporter)))) {
+            !((InsertReplaceEdit.canParse(textEdit, reporter) ||
+                TextEdit.canParse(textEdit, reporter)))) {
           reporter.reportError(
-              'must be of type Either2<TextEdit, InsertReplaceEdit>');
+              'must be of type Either2<InsertReplaceEdit, TextEdit>');
           return false;
         }
       } finally {
@@ -7769,15 +7769,14 @@ class CompletionListItemDefaults implements ToJsonable {
     final editRangeJson = json['editRange'];
     final editRange = editRangeJson == null
         ? null
-        : (Range.canParse(editRangeJson, nullLspJsonReporter)
-            ? Either2<Range, CompletionListEditRange>.t1(
-                Range.fromJson(editRangeJson as Map<String, Object?>))
-            : (CompletionListEditRange.canParse(
-                    editRangeJson, nullLspJsonReporter)
-                ? Either2<Range, CompletionListEditRange>.t2(
-                    CompletionListEditRange.fromJson(
-                        editRangeJson as Map<String, Object?>))
-                : (throw '''$editRangeJson was not one of (Range, CompletionListEditRange)''')));
+        : (CompletionListEditRange.canParse(editRangeJson, nullLspJsonReporter)
+            ? Either2<CompletionListEditRange, Range>.t1(
+                CompletionListEditRange.fromJson(
+                    editRangeJson as Map<String, Object?>))
+            : (Range.canParse(editRangeJson, nullLspJsonReporter)
+                ? Either2<CompletionListEditRange, Range>.t2(
+                    Range.fromJson(editRangeJson as Map<String, Object?>))
+                : (throw '''$editRangeJson was not one of (CompletionListEditRange, Range)''')));
     final insertTextFormatJson = json['insertTextFormat'];
     final insertTextFormat = insertTextFormatJson != null
         ? InsertTextFormat.fromJson(insertTextFormatJson as int)
@@ -7800,7 +7799,7 @@ class CompletionListItemDefaults implements ToJsonable {
 
   /// A default edit range
   ///  @since 3.17.0
-  final Either2<Range, CompletionListEditRange>? editRange;
+  final Either2<CompletionListEditRange, Range>? editRange;
 
   /// A default insert text format
   ///  @since 3.17.0
@@ -7845,10 +7844,10 @@ class CompletionListItemDefaults implements ToJsonable {
       try {
         final editRange = obj['editRange'];
         if (editRange != null &&
-            !((Range.canParse(editRange, reporter) ||
-                CompletionListEditRange.canParse(editRange, reporter)))) {
+            !((CompletionListEditRange.canParse(editRange, reporter) ||
+                Range.canParse(editRange, reporter)))) {
           reporter.reportError(
-              'must be of type Either2<Range, CompletionListEditRange>');
+              'must be of type Either2<CompletionListEditRange, Range>');
           return false;
         }
       } finally {
@@ -19269,12 +19268,12 @@ class Hover implements ToJsonable {
   });
   static Hover fromJson(Map<String, Object?> json) {
     final contentsJson = json['contents'];
-    final contents = contentsJson is String
-        ? Either2<String, MarkupContent>.t1(contentsJson)
-        : (MarkupContent.canParse(contentsJson, nullLspJsonReporter)
-            ? Either2<String, MarkupContent>.t2(
-                MarkupContent.fromJson(contentsJson as Map<String, Object?>))
-            : (throw '''$contentsJson was not one of (String, MarkupContent)'''));
+    final contents = MarkupContent.canParse(contentsJson, nullLspJsonReporter)
+        ? Either2<MarkupContent, String>.t1(
+            MarkupContent.fromJson(contentsJson as Map<String, Object?>))
+        : (contentsJson is String
+            ? Either2<MarkupContent, String>.t2(contentsJson)
+            : (throw '''$contentsJson was not one of (MarkupContent, String)'''));
     final rangeJson = json['range'];
     final range = rangeJson != null
         ? Range.fromJson(rangeJson as Map<String, Object?>)
@@ -19286,7 +19285,7 @@ class Hover implements ToJsonable {
   }
 
   /// The hover's content
-  final Either2<String, MarkupContent> contents;
+  final Either2<MarkupContent, String> contents;
 
   /// An optional range is a range inside a text document that is used to
   /// visualize a hover, e.g. by changing the background color.
@@ -19314,10 +19313,10 @@ class Hover implements ToJsonable {
           reporter.reportError('must not be null');
           return false;
         }
-        if (!((contents is String ||
-            MarkupContent.canParse(contents, reporter)))) {
+        if (!((MarkupContent.canParse(contents, reporter) ||
+            contents is String))) {
           reporter
-              .reportError('must be of type Either2<String, MarkupContent>');
+              .reportError('must be of type Either2<MarkupContent, String>');
           return false;
         }
       } finally {
@@ -21019,16 +21018,16 @@ class InlayHint implements ToJsonable {
     final positionJson = json['position'];
     final position = Position.fromJson(positionJson as Map<String, Object?>);
     final labelJson = json['label'];
-    final label = labelJson is String
-        ? Either2<String, List<InlayHintLabelPart>>.t1(labelJson)
-        : ((labelJson is List<Object?> &&
-                (labelJson.every((item) =>
-                    InlayHintLabelPart.canParse(item, nullLspJsonReporter))))
-            ? Either2<String, List<InlayHintLabelPart>>.t2((labelJson)
-                .map((item) =>
-                    InlayHintLabelPart.fromJson(item as Map<String, Object?>))
-                .toList())
-            : (throw '''$labelJson was not one of (String, List<InlayHintLabelPart>)'''));
+    final label = (labelJson is List<Object?> &&
+            (labelJson.every((item) =>
+                InlayHintLabelPart.canParse(item, nullLspJsonReporter))))
+        ? Either2<List<InlayHintLabelPart>, String>.t1((labelJson)
+            .map((item) =>
+                InlayHintLabelPart.fromJson(item as Map<String, Object?>))
+            .toList())
+        : (labelJson is String
+            ? Either2<List<InlayHintLabelPart>, String>.t2(labelJson)
+            : (throw '''$labelJson was not one of (List<InlayHintLabelPart>, String)'''));
     final kindJson = json['kind'];
     final kind =
         kindJson != null ? InlayHintKind.fromJson(kindJson as int) : null;
@@ -21039,12 +21038,12 @@ class InlayHint implements ToJsonable {
     final tooltipJson = json['tooltip'];
     final tooltip = tooltipJson == null
         ? null
-        : (tooltipJson is String
-            ? Either2<String, MarkupContent>.t1(tooltipJson)
-            : (MarkupContent.canParse(tooltipJson, nullLspJsonReporter)
-                ? Either2<String, MarkupContent>.t2(
-                    MarkupContent.fromJson(tooltipJson as Map<String, Object?>))
-                : (throw '''$tooltipJson was not one of (String, MarkupContent)''')));
+        : (MarkupContent.canParse(tooltipJson, nullLspJsonReporter)
+            ? Either2<MarkupContent, String>.t1(
+                MarkupContent.fromJson(tooltipJson as Map<String, Object?>))
+            : (tooltipJson is String
+                ? Either2<MarkupContent, String>.t2(tooltipJson)
+                : (throw '''$tooltipJson was not one of (MarkupContent, String)''')));
     final paddingLeftJson = json['paddingLeft'];
     final paddingLeft = paddingLeftJson as bool?;
     final paddingRightJson = json['paddingRight'];
@@ -21075,7 +21074,7 @@ class InlayHint implements ToJsonable {
   /// InlayHintLabelPart label parts.
   ///
   /// *Note* that neither the string nor the label part can be empty.
-  final Either2<String, List<InlayHintLabelPart>> label;
+  final Either2<List<InlayHintLabelPart>, String> label;
 
   /// Render padding before the hint.
   ///
@@ -21108,7 +21107,7 @@ class InlayHint implements ToJsonable {
   ///
   /// Depending on the client capability `inlayHint.resolveSupport` clients
   /// might resolve this property late using the resolve request.
-  final Either2<String, MarkupContent>? tooltip;
+  final Either2<MarkupContent, String>? tooltip;
 
   Map<String, Object?> toJson() {
     var __result = <String, Object?>{};
@@ -21166,12 +21165,12 @@ class InlayHint implements ToJsonable {
           reporter.reportError('must not be null');
           return false;
         }
-        if (!((label is String ||
-            (label is List<Object?> &&
-                (label.every((item) =>
-                    InlayHintLabelPart.canParse(item, reporter))))))) {
+        if (!(((label is List<Object?> &&
+                (label.every(
+                    (item) => InlayHintLabelPart.canParse(item, reporter)))) ||
+            label is String))) {
           reporter.reportError(
-              'must be of type Either2<String, List<InlayHintLabelPart>>');
+              'must be of type Either2<List<InlayHintLabelPart>, String>');
           return false;
         }
       } finally {
@@ -21204,10 +21203,10 @@ class InlayHint implements ToJsonable {
       try {
         final tooltip = obj['tooltip'];
         if (tooltip != null &&
-            !((tooltip is String ||
-                MarkupContent.canParse(tooltip, reporter)))) {
+            !((MarkupContent.canParse(tooltip, reporter) ||
+                tooltip is String))) {
           reporter
-              .reportError('must be of type Either2<String, MarkupContent>');
+              .reportError('must be of type Either2<MarkupContent, String>');
           return false;
         }
       } finally {
@@ -21495,12 +21494,12 @@ class InlayHintLabelPart implements ToJsonable {
     final tooltipJson = json['tooltip'];
     final tooltip = tooltipJson == null
         ? null
-        : (tooltipJson is String
-            ? Either2<String, MarkupContent>.t1(tooltipJson)
-            : (MarkupContent.canParse(tooltipJson, nullLspJsonReporter)
-                ? Either2<String, MarkupContent>.t2(
-                    MarkupContent.fromJson(tooltipJson as Map<String, Object?>))
-                : (throw '''$tooltipJson was not one of (String, MarkupContent)''')));
+        : (MarkupContent.canParse(tooltipJson, nullLspJsonReporter)
+            ? Either2<MarkupContent, String>.t1(
+                MarkupContent.fromJson(tooltipJson as Map<String, Object?>))
+            : (tooltipJson is String
+                ? Either2<MarkupContent, String>.t2(tooltipJson)
+                : (throw '''$tooltipJson was not one of (MarkupContent, String)''')));
     final locationJson = json['location'];
     final location = locationJson != null
         ? Location.fromJson(locationJson as Map<String, Object?>)
@@ -21538,7 +21537,7 @@ class InlayHintLabelPart implements ToJsonable {
   /// The tooltip text when you hover over this label part. Depending on the
   /// client capability `inlayHint.resolveSupport` clients might resolve this
   /// property late using the resolve request.
-  final Either2<String, MarkupContent>? tooltip;
+  final Either2<MarkupContent, String>? tooltip;
 
   /// The value of this label part.
   final String value;
@@ -21582,10 +21581,10 @@ class InlayHintLabelPart implements ToJsonable {
       try {
         final tooltip = obj['tooltip'];
         if (tooltip != null &&
-            !((tooltip is String ||
-                MarkupContent.canParse(tooltip, reporter)))) {
+            !((MarkupContent.canParse(tooltip, reporter) ||
+                tooltip is String))) {
           reporter
-              .reportError('must be of type Either2<String, MarkupContent>');
+              .reportError('must be of type Either2<MarkupContent, String>');
           return false;
         }
       } finally {
@@ -25808,24 +25807,21 @@ class NotebookCellTextDocumentFilter implements ToJsonable {
   });
   static NotebookCellTextDocumentFilter fromJson(Map<String, Object?> json) {
     final notebookJson = json['notebook'];
-    final notebook = notebookJson is String
-        ? Either2<String, Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>>.t1(
-            notebookJson)
-        : ((NotebookDocumentFilter1.canParse(notebookJson, nullLspJsonReporter) ||
-                NotebookDocumentFilter2.canParse(
-                    notebookJson, nullLspJsonReporter) ||
-                NotebookDocumentFilter3.canParse(
-                    notebookJson, nullLspJsonReporter))
-            ? Either2<String, Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>>.t2(
-                NotebookDocumentFilter1.canParse(notebookJson, nullLspJsonReporter)
-                    ? Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>.t1(
-                        NotebookDocumentFilter1.fromJson(
-                            notebookJson as Map<String, Object?>))
-                    : (NotebookDocumentFilter2.canParse(notebookJson, nullLspJsonReporter)
-                        ? Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>.t2(
-                            NotebookDocumentFilter2.fromJson(notebookJson as Map<String, Object?>))
-                        : (NotebookDocumentFilter3.canParse(notebookJson, nullLspJsonReporter) ? Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>.t3(NotebookDocumentFilter3.fromJson(notebookJson as Map<String, Object?>)) : (throw '''$notebookJson was not one of (NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3)'''))))
-            : (throw '''$notebookJson was not one of (String, Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>)'''));
+    final notebook = (NotebookDocumentFilter1.canParse(notebookJson, nullLspJsonReporter) ||
+            NotebookDocumentFilter2.canParse(
+                notebookJson, nullLspJsonReporter) ||
+            NotebookDocumentFilter3.canParse(notebookJson, nullLspJsonReporter))
+        ? Either2<Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>, String>.t1(
+            NotebookDocumentFilter1.canParse(notebookJson, nullLspJsonReporter)
+                ? Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>.t1(NotebookDocumentFilter1.fromJson(
+                    notebookJson as Map<String, Object?>))
+                : (NotebookDocumentFilter2.canParse(notebookJson, nullLspJsonReporter)
+                    ? Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>.t2(NotebookDocumentFilter2.fromJson(
+                        notebookJson as Map<String, Object?>))
+                    : (NotebookDocumentFilter3.canParse(notebookJson, nullLspJsonReporter)
+                        ? Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>.t3(NotebookDocumentFilter3.fromJson(notebookJson as Map<String, Object?>))
+                        : (throw '''$notebookJson was not one of (NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3)'''))))
+        : (notebookJson is String ? Either2<Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>, String>.t2(notebookJson) : (throw '''$notebookJson was not one of (Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>, String)'''));
     final languageJson = json['language'];
     final language = languageJson as String?;
     return NotebookCellTextDocumentFilter(
@@ -25844,9 +25840,9 @@ class NotebookCellTextDocumentFilter implements ToJsonable {
   /// If a string value is provided it matches against the notebook type. '*'
   /// matches every notebook.
   final Either2<
-      String,
       Either3<NotebookDocumentFilter1, NotebookDocumentFilter2,
-          NotebookDocumentFilter3>> notebook;
+          NotebookDocumentFilter3>,
+      String> notebook;
 
   Map<String, Object?> toJson() {
     var __result = <String, Object?>{};
@@ -25870,12 +25866,12 @@ class NotebookCellTextDocumentFilter implements ToJsonable {
           reporter.reportError('must not be null');
           return false;
         }
-        if (!((notebook is String ||
-            (NotebookDocumentFilter1.canParse(notebook, reporter) ||
+        if (!(((NotebookDocumentFilter1.canParse(notebook, reporter) ||
                 NotebookDocumentFilter2.canParse(notebook, reporter) ||
-                NotebookDocumentFilter3.canParse(notebook, reporter))))) {
+                NotebookDocumentFilter3.canParse(notebook, reporter)) ||
+            notebook is String))) {
           reporter.reportError(
-              'must be of type Either2<String, Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>>');
+              'must be of type Either2<Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>, String>');
           return false;
         }
       } finally {
@@ -27340,24 +27336,21 @@ class NotebookDocumentSyncOptionsNotebookSelector implements ToJsonable {
     final notebookDocumentJson = json['notebookDocument'];
     final notebookDocument = notebookDocumentJson == null
         ? null
-        : (notebookDocumentJson is String
-            ? Either2<String, Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>>.t1(
-                notebookDocumentJson)
-            : ((NotebookDocumentFilter1.canParse(notebookDocumentJson, nullLspJsonReporter) ||
-                    NotebookDocumentFilter2.canParse(
-                        notebookDocumentJson, nullLspJsonReporter) ||
-                    NotebookDocumentFilter3.canParse(
-                        notebookDocumentJson, nullLspJsonReporter))
-                ? Either2<String, Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>>.t2(
-                    NotebookDocumentFilter1.canParse(notebookDocumentJson, nullLspJsonReporter)
-                        ? Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>.t1(
-                            NotebookDocumentFilter1.fromJson(
-                                notebookDocumentJson as Map<String, Object?>))
-                        : (NotebookDocumentFilter2.canParse(
-                                notebookDocumentJson, nullLspJsonReporter)
-                            ? Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>.t2(NotebookDocumentFilter2.fromJson(notebookDocumentJson as Map<String, Object?>))
-                            : (NotebookDocumentFilter3.canParse(notebookDocumentJson, nullLspJsonReporter) ? Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>.t3(NotebookDocumentFilter3.fromJson(notebookDocumentJson as Map<String, Object?>)) : (throw '''$notebookDocumentJson was not one of (NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3)'''))))
-                : (throw '''$notebookDocumentJson was not one of (String, Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>)''')));
+        : ((NotebookDocumentFilter1.canParse(notebookDocumentJson, nullLspJsonReporter) ||
+                NotebookDocumentFilter2.canParse(
+                    notebookDocumentJson, nullLspJsonReporter) ||
+                NotebookDocumentFilter3.canParse(
+                    notebookDocumentJson, nullLspJsonReporter))
+            ? Either2<Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>, String>.t1(
+                NotebookDocumentFilter1.canParse(notebookDocumentJson, nullLspJsonReporter)
+                    ? Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>.t1(
+                        NotebookDocumentFilter1.fromJson(
+                            notebookDocumentJson as Map<String, Object?>))
+                    : (NotebookDocumentFilter2.canParse(notebookDocumentJson, nullLspJsonReporter)
+                        ? Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>.t2(
+                            NotebookDocumentFilter2.fromJson(notebookDocumentJson as Map<String, Object?>))
+                        : (NotebookDocumentFilter3.canParse(notebookDocumentJson, nullLspJsonReporter) ? Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>.t3(NotebookDocumentFilter3.fromJson(notebookDocumentJson as Map<String, Object?>)) : (throw '''$notebookDocumentJson was not one of (NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3)'''))))
+            : (notebookDocumentJson is String ? Either2<Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>, String>.t2(notebookDocumentJson) : (throw '''$notebookDocumentJson was not one of (Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>, String)''')));
     final cellsJson = json['cells'];
     final cells = (cellsJson as List<Object?>)
         .map((item) => NotebookDocumentSyncOptionsCells.fromJson(
@@ -27375,9 +27368,9 @@ class NotebookDocumentSyncOptionsNotebookSelector implements ToJsonable {
   /// The notebook to be synced If a string value is provided it matches against
   /// the notebook type. '*' matches every notebook.
   final Either2<
-      String,
       Either3<NotebookDocumentFilter1, NotebookDocumentFilter2,
-          NotebookDocumentFilter3>>? notebookDocument;
+          NotebookDocumentFilter3>,
+      String>? notebookDocument;
 
   Map<String, Object?> toJson() {
     var __result = <String, Object?>{};
@@ -27394,14 +27387,14 @@ class NotebookDocumentSyncOptionsNotebookSelector implements ToJsonable {
       try {
         final notebookDocument = obj['notebookDocument'];
         if (notebookDocument != null &&
-            !((notebookDocument is String ||
-                (NotebookDocumentFilter1.canParse(notebookDocument, reporter) ||
+            !(((NotebookDocumentFilter1.canParse(notebookDocument, reporter) ||
                     NotebookDocumentFilter2.canParse(
                         notebookDocument, reporter) ||
                     NotebookDocumentFilter3.canParse(
-                        notebookDocument, reporter))))) {
+                        notebookDocument, reporter)) ||
+                notebookDocument is String))) {
           reporter.reportError(
-              'must be of type Either2<String, Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>>');
+              'must be of type Either2<Either3<NotebookDocumentFilter1, NotebookDocumentFilter2, NotebookDocumentFilter3>, String>');
           return false;
         }
       } finally {
@@ -27855,12 +27848,12 @@ class ParameterInformation implements ToJsonable {
     final documentationJson = json['documentation'];
     final documentation = documentationJson == null
         ? null
-        : (documentationJson is String
-            ? Either2<String, MarkupContent>.t1(documentationJson)
-            : (MarkupContent.canParse(documentationJson, nullLspJsonReporter)
-                ? Either2<String, MarkupContent>.t2(MarkupContent.fromJson(
-                    documentationJson as Map<String, Object?>))
-                : (throw '''$documentationJson was not one of (String, MarkupContent)''')));
+        : (MarkupContent.canParse(documentationJson, nullLspJsonReporter)
+            ? Either2<MarkupContent, String>.t1(MarkupContent.fromJson(
+                documentationJson as Map<String, Object?>))
+            : (documentationJson is String
+                ? Either2<MarkupContent, String>.t2(documentationJson)
+                : (throw '''$documentationJson was not one of (MarkupContent, String)''')));
     return ParameterInformation(
       label: label,
       documentation: documentation,
@@ -27869,7 +27862,7 @@ class ParameterInformation implements ToJsonable {
 
   /// The human-readable doc-comment of this parameter. Will be shown in the UI
   /// but can be omitted.
-  final Either2<String, MarkupContent>? documentation;
+  final Either2<MarkupContent, String>? documentation;
 
   /// The label of this parameter information.
   ///
@@ -27916,10 +27909,10 @@ class ParameterInformation implements ToJsonable {
       try {
         final documentation = obj['documentation'];
         if (documentation != null &&
-            !((documentation is String ||
-                MarkupContent.canParse(documentation, reporter)))) {
+            !((MarkupContent.canParse(documentation, reporter) ||
+                documentation is String))) {
           reporter
-              .reportError('must be of type Either2<String, MarkupContent>');
+              .reportError('must be of type Either2<MarkupContent, String>');
           return false;
         }
       } finally {
@@ -30268,12 +30261,12 @@ class RelativePattern implements ToJsonable {
   });
   static RelativePattern fromJson(Map<String, Object?> json) {
     final baseUriJson = json['baseUri'];
-    final baseUri = WorkspaceFolder.canParse(baseUriJson, nullLspJsonReporter)
-        ? Either2<WorkspaceFolder, String>.t1(
-            WorkspaceFolder.fromJson(baseUriJson as Map<String, Object?>))
-        : (baseUriJson is String
-            ? Either2<WorkspaceFolder, String>.t2(baseUriJson)
-            : (throw '''$baseUriJson was not one of (WorkspaceFolder, String)'''));
+    final baseUri = baseUriJson is String
+        ? Either2<String, WorkspaceFolder>.t1(baseUriJson)
+        : (WorkspaceFolder.canParse(baseUriJson, nullLspJsonReporter)
+            ? Either2<String, WorkspaceFolder>.t2(
+                WorkspaceFolder.fromJson(baseUriJson as Map<String, Object?>))
+            : (throw '''$baseUriJson was not one of (String, WorkspaceFolder)'''));
     final patternJson = json['pattern'];
     final pattern = patternJson as String;
     return RelativePattern(
@@ -30284,7 +30277,7 @@ class RelativePattern implements ToJsonable {
 
   /// A workspace folder or a base URI to which this pattern will be matched
   /// against relatively.
-  final Either2<WorkspaceFolder, String> baseUri;
+  final Either2<String, WorkspaceFolder> baseUri;
 
   /// The actual glob pattern;
   final String pattern;
@@ -30309,10 +30302,10 @@ class RelativePattern implements ToJsonable {
           reporter.reportError('must not be null');
           return false;
         }
-        if (!((WorkspaceFolder.canParse(baseUri, reporter) ||
-            baseUri is String))) {
+        if (!((baseUri is String ||
+            WorkspaceFolder.canParse(baseUri, reporter)))) {
           reporter
-              .reportError('must be of type Either2<WorkspaceFolder, String>');
+              .reportError('must be of type Either2<String, WorkspaceFolder>');
           return false;
         }
       } finally {
@@ -34519,16 +34512,16 @@ class ServerCapabilities implements ToJsonable {
     final textDocumentSyncJson = json['textDocumentSync'];
     final textDocumentSync = textDocumentSyncJson == null
         ? null
-        : (TextDocumentSyncOptions.canParse(
+        : (TextDocumentSyncKind.canParse(
                 textDocumentSyncJson, nullLspJsonReporter)
-            ? Either2<TextDocumentSyncOptions, TextDocumentSyncKind>.t1(
-                TextDocumentSyncOptions.fromJson(
-                    textDocumentSyncJson as Map<String, Object?>))
-            : (TextDocumentSyncKind.canParse(
+            ? Either2<TextDocumentSyncKind, TextDocumentSyncOptions>.t1(
+                TextDocumentSyncKind.fromJson(textDocumentSyncJson as int))
+            : (TextDocumentSyncOptions.canParse(
                     textDocumentSyncJson, nullLspJsonReporter)
-                ? Either2<TextDocumentSyncOptions, TextDocumentSyncKind>.t2(
-                    TextDocumentSyncKind.fromJson(textDocumentSyncJson as int))
-                : (throw '''$textDocumentSyncJson was not one of (TextDocumentSyncOptions, TextDocumentSyncKind)''')));
+                ? Either2<TextDocumentSyncKind, TextDocumentSyncOptions>.t2(
+                    TextDocumentSyncOptions.fromJson(
+                        textDocumentSyncJson as Map<String, Object?>))
+                : (throw '''$textDocumentSyncJson was not one of (TextDocumentSyncKind, TextDocumentSyncOptions)''')));
     final notebookDocumentSyncJson = json['notebookDocumentSync'];
     final notebookDocumentSync = notebookDocumentSyncJson == null
         ? null
@@ -35096,7 +35089,7 @@ class ServerCapabilities implements ToJsonable {
   /// defining each notification or for backwards compatibility the
   /// TextDocumentSyncKind number. If omitted it defaults to
   /// `TextDocumentSyncKind.None`.
-  final Either2<TextDocumentSyncOptions, TextDocumentSyncKind>?
+  final Either2<TextDocumentSyncKind, TextDocumentSyncOptions>?
       textDocumentSync;
 
   /// The server provides goto type definition support.
@@ -35244,10 +35237,11 @@ class ServerCapabilities implements ToJsonable {
       try {
         final textDocumentSync = obj['textDocumentSync'];
         if (textDocumentSync != null &&
-            !((TextDocumentSyncOptions.canParse(textDocumentSync, reporter) ||
-                TextDocumentSyncKind.canParse(textDocumentSync, reporter)))) {
+            !((TextDocumentSyncKind.canParse(textDocumentSync, reporter) ||
+                TextDocumentSyncOptions.canParse(
+                    textDocumentSync, reporter)))) {
           reporter.reportError(
-              'must be of type Either2<TextDocumentSyncOptions, TextDocumentSyncKind>');
+              'must be of type Either2<TextDocumentSyncKind, TextDocumentSyncOptions>');
           return false;
         }
       } finally {
@@ -37953,12 +37947,12 @@ class SignatureInformation implements ToJsonable {
     final documentationJson = json['documentation'];
     final documentation = documentationJson == null
         ? null
-        : (documentationJson is String
-            ? Either2<String, MarkupContent>.t1(documentationJson)
-            : (MarkupContent.canParse(documentationJson, nullLspJsonReporter)
-                ? Either2<String, MarkupContent>.t2(MarkupContent.fromJson(
-                    documentationJson as Map<String, Object?>))
-                : (throw '''$documentationJson was not one of (String, MarkupContent)''')));
+        : (MarkupContent.canParse(documentationJson, nullLspJsonReporter)
+            ? Either2<MarkupContent, String>.t1(MarkupContent.fromJson(
+                documentationJson as Map<String, Object?>))
+            : (documentationJson is String
+                ? Either2<MarkupContent, String>.t2(documentationJson)
+                : (throw '''$documentationJson was not one of (MarkupContent, String)''')));
     final parametersJson = json['parameters'];
     final parameters = (parametersJson as List<Object?>?)
         ?.map((item) =>
@@ -37982,7 +37976,7 @@ class SignatureInformation implements ToJsonable {
 
   /// The human-readable doc-comment of this signature. Will be shown in the UI
   /// but can be omitted.
-  final Either2<String, MarkupContent>? documentation;
+  final Either2<MarkupContent, String>? documentation;
 
   /// The label of this signature. Will be shown in the UI.
   final String label;
@@ -38030,10 +38024,10 @@ class SignatureInformation implements ToJsonable {
       try {
         final documentation = obj['documentation'];
         if (documentation != null &&
-            !((documentation is String ||
-                MarkupContent.canParse(documentation, reporter)))) {
+            !((MarkupContent.canParse(documentation, reporter) ||
+                documentation is String))) {
           reporter
-              .reportError('must be of type Either2<String, MarkupContent>');
+              .reportError('must be of type Either2<MarkupContent, String>');
           return false;
         }
       } finally {
@@ -39683,16 +39677,16 @@ class TextDocumentEdit implements ToJsonable {
         textDocumentJson as Map<String, Object?>);
     final editsJson = json['edits'];
     final edits = (editsJson as List<Object?>)
-        .map((item) => SnippetTextEdit.canParse(item, nullLspJsonReporter)
-            ? Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>.t1(
-                SnippetTextEdit.fromJson(item as Map<String, Object?>))
-            : (AnnotatedTextEdit.canParse(item, nullLspJsonReporter)
-                ? Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>.t2(
-                    AnnotatedTextEdit.fromJson(item as Map<String, Object?>))
+        .map((item) => AnnotatedTextEdit.canParse(item, nullLspJsonReporter)
+            ? Either3<AnnotatedTextEdit, SnippetTextEdit, TextEdit>.t1(
+                AnnotatedTextEdit.fromJson(item as Map<String, Object?>))
+            : (SnippetTextEdit.canParse(item, nullLspJsonReporter)
+                ? Either3<AnnotatedTextEdit, SnippetTextEdit, TextEdit>.t2(
+                    SnippetTextEdit.fromJson(item as Map<String, Object?>))
                 : (TextEdit.canParse(item, nullLspJsonReporter)
-                    ? Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>.t3(
+                    ? Either3<AnnotatedTextEdit, SnippetTextEdit, TextEdit>.t3(
                         TextEdit.fromJson(item as Map<String, Object?>))
-                    : (throw '''$item was not one of (SnippetTextEdit, AnnotatedTextEdit, TextEdit)'''))))
+                    : (throw '''$item was not one of (AnnotatedTextEdit, SnippetTextEdit, TextEdit)'''))))
         .toList();
     return TextDocumentEdit(
       textDocument: textDocument,
@@ -39703,7 +39697,7 @@ class TextDocumentEdit implements ToJsonable {
   /// The edits to be applied.
   ///  @since 3.16.0 - support for AnnotatedTextEdit. This is guarded by the
   /// client capability `workspace.workspaceEdit.changeAnnotationSupport`
-  final List<Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>> edits;
+  final List<Either3<AnnotatedTextEdit, SnippetTextEdit, TextEdit>> edits;
 
   /// The text document to change.
   final OptionalVersionedTextDocumentIdentifier textDocument;
@@ -39749,11 +39743,12 @@ class TextDocumentEdit implements ToJsonable {
           return false;
         }
         if (!((edits is List<Object?> &&
-            (edits.every((item) => (SnippetTextEdit.canParse(item, reporter) ||
-                AnnotatedTextEdit.canParse(item, reporter) ||
-                TextEdit.canParse(item, reporter))))))) {
+            (edits.every((item) =>
+                (AnnotatedTextEdit.canParse(item, reporter) ||
+                    SnippetTextEdit.canParse(item, reporter) ||
+                    TextEdit.canParse(item, reporter))))))) {
           reporter.reportError(
-              'must be of type List<Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>>');
+              'must be of type List<Either3<AnnotatedTextEdit, SnippetTextEdit, TextEdit>>');
           return false;
         }
       } finally {
@@ -39773,8 +39768,8 @@ class TextDocumentEdit implements ToJsonable {
           listEqual(
               edits,
               other.edits,
-              (Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit> a,
-                      Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>
+              (Either3<AnnotatedTextEdit, SnippetTextEdit, TextEdit> a,
+                      Either3<AnnotatedTextEdit, SnippetTextEdit, TextEdit>
                           b) =>
                   a == b) &&
           true;
@@ -44246,20 +44241,22 @@ class WorkspaceEdit implements ToJsonable {
         ? null
         : ((documentChangesJson is List<Object?> &&
                 (documentChangesJson.every((item) =>
-                    TextDocumentEdit.canParse(item, nullLspJsonReporter))))
-            ? Either2<List<TextDocumentEdit>, List<Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>>>.t1((documentChangesJson)
-                .map((item) =>
-                    TextDocumentEdit.fromJson(item as Map<String, Object?>))
+                    (CreateFile.canParse(item, nullLspJsonReporter) ||
+                        DeleteFile.canParse(item, nullLspJsonReporter) ||
+                        RenameFile.canParse(item, nullLspJsonReporter) ||
+                        TextDocumentEdit.canParse(item, nullLspJsonReporter)))))
+            ? Either2<List<Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>>, List<TextDocumentEdit>>.t1((documentChangesJson)
+                .map((item) => CreateFile.canParse(item, nullLspJsonReporter)
+                    ? Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>.t1(
+                        CreateFile.fromJson(item as Map<String, Object?>))
+                    : (DeleteFile.canParse(item, nullLspJsonReporter)
+                        ? Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>.t2(
+                            DeleteFile.fromJson(item as Map<String, Object?>))
+                        : (RenameFile.canParse(item, nullLspJsonReporter)
+                            ? Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>.t3(RenameFile.fromJson(item as Map<String, Object?>))
+                            : (TextDocumentEdit.canParse(item, nullLspJsonReporter) ? Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>.t4(TextDocumentEdit.fromJson(item as Map<String, Object?>)) : (throw '''$item was not one of (CreateFile, DeleteFile, RenameFile, TextDocumentEdit)''')))))
                 .toList())
-            : ((documentChangesJson is List<Object?> &&
-                    (documentChangesJson.every((item) =>
-                        (TextDocumentEdit.canParse(item, nullLspJsonReporter) ||
-                            CreateFile.canParse(item, nullLspJsonReporter) ||
-                            RenameFile.canParse(item, nullLspJsonReporter) ||
-                            DeleteFile.canParse(item, nullLspJsonReporter)))))
-                ? Either2<List<TextDocumentEdit>, List<Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>>>.t2(
-                    (documentChangesJson).map((item) => TextDocumentEdit.canParse(item, nullLspJsonReporter) ? Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>.t1(TextDocumentEdit.fromJson(item as Map<String, Object?>)) : (CreateFile.canParse(item, nullLspJsonReporter) ? Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>.t2(CreateFile.fromJson(item as Map<String, Object?>)) : (RenameFile.canParse(item, nullLspJsonReporter) ? Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>.t3(RenameFile.fromJson(item as Map<String, Object?>)) : (DeleteFile.canParse(item, nullLspJsonReporter) ? Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>.t4(DeleteFile.fromJson(item as Map<String, Object?>)) : (throw '''$item was not one of (TextDocumentEdit, CreateFile, RenameFile, DeleteFile)'''))))).toList())
-                : (throw '''$documentChangesJson was not one of (List<TextDocumentEdit>, List<Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>>)''')));
+            : ((documentChangesJson is List<Object?> && (documentChangesJson.every((item) => TextDocumentEdit.canParse(item, nullLspJsonReporter)))) ? Either2<List<Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>>, List<TextDocumentEdit>>.t2((documentChangesJson).map((item) => TextDocumentEdit.fromJson(item as Map<String, Object?>)).toList()) : (throw '''$documentChangesJson was not one of (List<Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>>, List<TextDocumentEdit>)''')));
     final changeAnnotationsJson = json['changeAnnotations'];
     final changeAnnotations = (changeAnnotationsJson as Map<Object, Object?>?)
         ?.map((key, value) => MapEntry(key as String,
@@ -44295,9 +44292,9 @@ class WorkspaceEdit implements ToJsonable {
   /// If a client neither supports `documentChanges` nor
   /// `workspace.workspaceEdit.resourceOperations` then only plain `TextEdit`s
   /// using the `changes` property are supported.
-  final Either2<List<TextDocumentEdit>,
-          List<Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>>>?
-      documentChanges;
+  final Either2<
+      List<Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>>,
+      List<TextDocumentEdit>>? documentChanges;
 
   Map<String, Object?> toJson() {
     var __result = <String, Object?>{};
@@ -44337,15 +44334,15 @@ class WorkspaceEdit implements ToJsonable {
         if (documentChanges != null &&
             !(((documentChanges is List<Object?> &&
                     (documentChanges.every((item) =>
-                        TextDocumentEdit.canParse(item, reporter)))) ||
+                        (CreateFile.canParse(item, reporter) ||
+                            DeleteFile.canParse(item, reporter) ||
+                            RenameFile.canParse(item, reporter) ||
+                            TextDocumentEdit.canParse(item, reporter))))) ||
                 (documentChanges is List<Object?> &&
                     (documentChanges.every((item) =>
-                        (TextDocumentEdit.canParse(item, reporter) ||
-                            CreateFile.canParse(item, reporter) ||
-                            RenameFile.canParse(item, reporter) ||
-                            DeleteFile.canParse(item, reporter)))))))) {
+                        TextDocumentEdit.canParse(item, reporter))))))) {
           reporter.reportError(
-              'must be of type Either2<List<TextDocumentEdit>, List<Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>>>');
+              'must be of type Either2<List<Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>>, List<TextDocumentEdit>>');
           return false;
         }
       } finally {
@@ -44875,11 +44872,11 @@ class WorkspaceFoldersServerCapabilities implements ToJsonable {
     final changeNotificationsJson = json['changeNotifications'];
     final changeNotifications = changeNotificationsJson == null
         ? null
-        : (changeNotificationsJson is String
-            ? Either2<String, bool>.t1(changeNotificationsJson)
-            : (changeNotificationsJson is bool
-                ? Either2<String, bool>.t2(changeNotificationsJson)
-                : (throw '''$changeNotificationsJson was not one of (String, bool)''')));
+        : (changeNotificationsJson is bool
+            ? Either2<bool, String>.t1(changeNotificationsJson)
+            : (changeNotificationsJson is String
+                ? Either2<bool, String>.t2(changeNotificationsJson)
+                : (throw '''$changeNotificationsJson was not one of (bool, String)''')));
     return WorkspaceFoldersServerCapabilities(
       supported: supported,
       changeNotifications: changeNotifications,
@@ -44892,7 +44889,7 @@ class WorkspaceFoldersServerCapabilities implements ToJsonable {
   /// notification is registered on the client side. The ID can be used to
   /// unregister for these events using the `client/unregisterCapability`
   /// request.
-  final Either2<String, bool>? changeNotifications;
+  final Either2<bool, String>? changeNotifications;
 
   /// The server has support for workspace folders
   final bool? supported;
@@ -44924,8 +44921,8 @@ class WorkspaceFoldersServerCapabilities implements ToJsonable {
       try {
         final changeNotifications = obj['changeNotifications'];
         if (changeNotifications != null &&
-            !((changeNotifications is String || changeNotifications is bool))) {
-          reporter.reportError('must be of type Either2<String, bool>');
+            !((changeNotifications is bool || changeNotifications is String))) {
+          reporter.reportError('must be of type Either2<bool, String>');
           return false;
         }
       } finally {

pkg/analysis_server/lib/src/computer/computer_type_arguments_signature.dart

@@ -98,7 +98,7 @@ class DartTypeArgumentsSignatureComputer {
       lsp.SignatureInformation(
         label: label,
         documentation: documentation != null
-            ? asStringOrMarkupContent(preferredFormats, documentation)
+            ? asMarkupContentOrString(preferredFormats, documentation)
             : null,
         parameters: parameters,
       ),

pkg/analysis_server/lib/src/lsp/handlers/handler_completion_resolve.dart

@@ -120,7 +120,7 @@ class CompletionResolveHandler
         final dartDoc =
             analyzer.getDartDocPlainText(element.documentationComment);
         final documentation =
-            dartDoc != null ? asStringOrMarkupContent(formats, dartDoc) : null;
+            dartDoc != null ? asMarkupContentOrString(formats, dartDoc) : null;
         final supportsInsertReplace =
             clientCapabilities.insertReplaceCompletionRanges;
 
@@ -152,14 +152,14 @@ class CompletionResolveHandler
           insertText: newInsertText,
           insertTextFormat: item.insertTextFormat,
           textEdit: supportsInsertReplace && insertionRange != replacementRange
-              ? Either2<TextEdit, InsertReplaceEdit>.t2(
+              ? Either2<InsertReplaceEdit, TextEdit>.t1(
                   InsertReplaceEdit(
                     insert: insertionRange,
                     replace: replacementRange,
                     newText: newInsertText,
                   ),
                 )
-              : Either2<TextEdit, InsertReplaceEdit>.t1(
+              : Either2<InsertReplaceEdit, TextEdit>.t2(
                   TextEdit(
                     range: replacementRange,
                     newText: newInsertText,
@@ -253,7 +253,7 @@ class CompletionResolveHandler
       tags: item.tags,
       detail: item.detail,
       documentation: description != null
-          ? Either2<String, MarkupContent>.t1(description)
+          ? Either2<MarkupContent, String>.t2(description)
           : null,
       deprecated: item.deprecated,
       preselect: item.preselect,

pkg/analysis_server/lib/src/lsp/handlers/handler_hover.dart

@@ -84,7 +84,7 @@ class HoverHandler extends MessageHandler<TextDocumentPositionParams, Hover?> {
     final formats = server.clientCapabilities?.hoverContentFormats;
     return Hover(
       contents:
-          asStringOrMarkupContent(formats, content.toString().trimRight()),
+          asMarkupContentOrString(formats, content.toString().trimRight()),
       range: toRange(lineInfo, hover.offset, hover.length),
     );
   }

pkg/analysis_server/lib/src/lsp/mapping.dart

@@ -57,12 +57,12 @@ final diagnosticTagsForErrorCode = <String, List<lsp.DiagnosticTag>>{
 /// field.
 final _upgradableDocCompletePattern = RegExp(r'^_([\w ]{0,20})_$');
 
-lsp.Either2<String, lsp.MarkupContent> asStringOrMarkupContent(
+lsp.Either2<lsp.MarkupContent, String> asMarkupContentOrString(
     Set<lsp.MarkupKind>? preferredFormats, String content) {
-  return preferredFormats == null
-      ? lsp.Either2<String, lsp.MarkupContent>.t1(content)
-      : lsp.Either2<String, lsp.MarkupContent>.t2(
-          _asMarkup(preferredFormats, content));
+  return preferredFormats != null
+      ? lsp.Either2<lsp.MarkupContent, String>.t1(
+          _asMarkup(preferredFormats, content))
+      : lsp.Either2<lsp.MarkupContent, String>.t2(content);
 }
 
 /// Creates a [lsp.WorkspaceEdit] from simple [server.SourceFileEdit]s.
@@ -93,7 +93,7 @@ lsp.WorkspaceEdit createPlainWorkspaceEdit(
 /// Create a [WorkspaceEdit] that renames [oldPath] to [newPath].
 WorkspaceEdit createRenameEdit(String oldPath, String newPath) {
   final changes =
-      <Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>>[];
+      <Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>>[];
 
   final rename = RenameFile(
     oldUri: Uri.file(oldPath).toString(),
@@ -101,16 +101,14 @@ WorkspaceEdit createRenameEdit(String oldPath, String newPath) {
   );
 
   final renameUnion =
-      Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>.t3(rename);
+      Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>.t3(rename);
 
   changes.add(renameUnion);
 
   final edit = WorkspaceEdit(
       documentChanges: Either2<
-          List<TextDocumentEdit>,
-          List<
-              Either4<TextDocumentEdit, CreateFile, RenameFile,
-                  DeleteFile>>>.t2(changes));
+          List<Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>>,
+          List<TextDocumentEdit>>.t1(changes));
   return edit;
 }
 
@@ -164,21 +162,21 @@ lsp.WorkspaceEdit createWorkspaceEdit(
   final textDocumentEdit = lsp.TextDocumentEdit(
     textDocument: server.getVersionedDocumentIdentifier(fileEdit.file),
     edits: snippetEdits
-        .map((e) => Either3<lsp.SnippetTextEdit, lsp.AnnotatedTextEdit,
-            lsp.TextEdit>.t1(e))
+        .map((e) => Either3<lsp.AnnotatedTextEdit, lsp.SnippetTextEdit,
+            lsp.TextEdit>.t2(e))
         .toList(),
   );
 
   // Convert to the union that documentChanges require.
-  final textDocumentEditsAsUnion = Either4<lsp.TextDocumentEdit, lsp.CreateFile,
-      lsp.RenameFile, lsp.DeleteFile>.t1(textDocumentEdit);
+  final textDocumentEditsAsUnion = Either4<lsp.CreateFile, lsp.DeleteFile,
+      lsp.RenameFile, lsp.TextDocumentEdit>.t4(textDocumentEdit);
 
   // Convert to the union that documentChanges is.
   final documentChanges = Either2<
-      List<lsp.TextDocumentEdit>,
       List<
-          Either4<lsp.TextDocumentEdit, lsp.CreateFile, lsp.RenameFile,
-              lsp.DeleteFile>>>.t2([textDocumentEditsAsUnion]);
+          Either4<lsp.CreateFile, lsp.DeleteFile, lsp.RenameFile,
+              lsp.TextDocumentEdit>>,
+      List<lsp.TextDocumentEdit>>.t1([textDocumentEditsAsUnion]);
 
   /// Add the textDocumentEdit to a WorkspaceEdit.
   return lsp.WorkspaceEdit(documentChanges: documentChanges);
@@ -695,24 +693,22 @@ WorkspaceEdit mergeWorkspaceEdits(List<WorkspaceEdit> edits) {
   // TODO(dantup): This method (and much other code here) should be
   // significantly tidied up when nonfunction-type-aliases is available here.
   final changes =
-      <Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>>[];
+      <Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>>[];
 
   for (final edit in edits) {
     // Flatten the Either into just the Union side to get a flat list.
     final flatResourceChanges = edit.documentChanges!.map(
-      (edits) => edits.map((e) =>
-          Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>.t1(e)),
       (resources) => resources,
+      (edits) => edits.map((e) =>
+          Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>.t4(e)),
     );
     changes.addAll(flatResourceChanges);
   }
 
   return WorkspaceEdit(
       documentChanges: Either2<
-          List<TextDocumentEdit>,
-          List<
-              Either4<TextDocumentEdit, CreateFile, RenameFile,
-                  DeleteFile>>>.t2(changes));
+          List<Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>>,
+          List<TextDocumentEdit>>.t1(changes));
 }
 
 lsp.Location navigationTargetToLocation(
@@ -1022,7 +1018,7 @@ lsp.CompletionItem snippetToCompletionItem(
     kind: lsp.CompletionItemKind.Snippet,
     command: command,
     documentation: documentation != null
-        ? asStringOrMarkupContent(formats, documentation)
+        ? asMarkupContentOrString(formats, documentation)
         : null,
     // Force snippets to be sorted at the bottom of the list.
     // TODO(dantup): Consider if we can rank these better. Client-side
@@ -1031,7 +1027,7 @@ lsp.CompletionItem snippetToCompletionItem(
     sortText: 'zzz${snippet.prefix}',
     insertTextFormat: lsp.InsertTextFormat.Snippet,
     insertTextMode: supportsAsIsInsertMode ? InsertTextMode.asIs : null,
-    textEdit: Either2<TextEdit, InsertReplaceEdit>.t1(mainEdit),
+    textEdit: Either2<InsertReplaceEdit, TextEdit>.t2(mainEdit),
     additionalTextEdits: nonMainEdits,
   );
 }
@@ -1222,7 +1218,7 @@ lsp.CompletionItem toCompletionItem(
     data: resolutionData,
     detail: detail,
     documentation: cleanedDoc != null
-        ? asStringOrMarkupContent(formats, cleanedDoc)
+        ? asMarkupContentOrString(formats, cleanedDoc)
         : null,
     deprecated: supportsCompletionDeprecatedFlag && suggestion.isDeprecated
         ? true
@@ -1243,14 +1239,14 @@ lsp.CompletionItem toCompletionItem(
     textEdit: (insertionRange == null || replacementRange == null)
         ? null
         : supportsInsertReplace && insertionRange != replacementRange
-            ? Either2<TextEdit, InsertReplaceEdit>.t2(
+            ? Either2<InsertReplaceEdit, TextEdit>.t1(
                 InsertReplaceEdit(
                   insert: insertionRange,
                   replace: replacementRange,
                   newText: insertText,
                 ),
               )
-            : Either2<TextEdit, InsertReplaceEdit>.t1(
+            : Either2<InsertReplaceEdit, TextEdit>.t2(
                 TextEdit(
                   range: replacementRange,
                   newText: insertText,
@@ -1476,7 +1472,7 @@ lsp.SignatureHelp toSignatureHelp(Set<lsp.MarkupKind>? preferredFormats,
       lsp.SignatureInformation(
         label: getSignatureLabel(signature),
         documentation: cleanedDoc != null
-            ? asStringOrMarkupContent(preferredFormats, cleanedDoc)
+            ? asMarkupContentOrString(preferredFormats, cleanedDoc)
             : null,
         parameters: signature.parameters.map(toParameterInfo).toList(),
       ),
@@ -1562,7 +1558,7 @@ lsp.TextDocumentEdit toTextDocumentEdit(
           .toList());
 }
 
-Either3<lsp.SnippetTextEdit, lsp.AnnotatedTextEdit, lsp.TextEdit>
+Either3<lsp.AnnotatedTextEdit, lsp.SnippetTextEdit, lsp.TextEdit>
     toTextDocumentEditEdit(
   LspClientCapabilities capabilities,
   server.LineInfo lineInfo,
@@ -1572,10 +1568,10 @@ Either3<lsp.SnippetTextEdit, lsp.AnnotatedTextEdit, lsp.TextEdit>
 }) {
   if (!capabilities.experimentalSnippetTextEdit ||
       selectionOffsetRelative == null) {
-    return Either3<lsp.SnippetTextEdit, lsp.AnnotatedTextEdit, lsp.TextEdit>.t3(
+    return Either3<lsp.AnnotatedTextEdit, lsp.SnippetTextEdit, lsp.TextEdit>.t3(
         toTextEdit(lineInfo, edit));
   }
-  return Either3<lsp.SnippetTextEdit, lsp.AnnotatedTextEdit, lsp.TextEdit>.t1(
+  return Either3<lsp.AnnotatedTextEdit, lsp.SnippetTextEdit, lsp.TextEdit>.t2(
       snippetTextEditWithSelection(lineInfo, edit,
           selectionOffsetRelative: selectionOffsetRelative,
           selectionLength: selectionLength));
@@ -1596,8 +1592,8 @@ lsp.WorkspaceEdit toWorkspaceEdit(
   if (supportsDocumentChanges) {
     final supportsCreate = capabilities.createResourceOperations;
     final changes = <
-        Either4<lsp.TextDocumentEdit, lsp.CreateFile, lsp.RenameFile,
-            lsp.DeleteFile>>[];
+        Either4<lsp.CreateFile, lsp.DeleteFile, lsp.RenameFile,
+            lsp.TextDocumentEdit>>[];
 
     // Convert each SourceEdit to either a TextDocumentEdit or a
     // CreateFile + a TextDocumentEdit depending on whether it's a new
@@ -1605,23 +1601,23 @@ lsp.WorkspaceEdit toWorkspaceEdit(
     for (final edit in edits) {
       if (supportsCreate && edit.newFile) {
         final create = lsp.CreateFile(uri: edit.doc.uri);
-        final createUnion = Either4<lsp.TextDocumentEdit, lsp.CreateFile,
-            lsp.RenameFile, lsp.DeleteFile>.t2(create);
+        final createUnion = Either4<lsp.CreateFile, lsp.DeleteFile,
+            lsp.RenameFile, lsp.TextDocumentEdit>.t1(create);
         changes.add(createUnion);
       }
 
       final textDocEdit = toTextDocumentEdit(capabilities, edit);
-      final textDocEditUnion = Either4<lsp.TextDocumentEdit, lsp.CreateFile,
-          lsp.RenameFile, lsp.DeleteFile>.t1(textDocEdit);
+      final textDocEditUnion = Either4<lsp.CreateFile, lsp.DeleteFile,
+          lsp.RenameFile, lsp.TextDocumentEdit>.t4(textDocEdit);
       changes.add(textDocEditUnion);
     }
 
     return lsp.WorkspaceEdit(
         documentChanges: Either2<
-            List<lsp.TextDocumentEdit>,
             List<
-                Either4<lsp.TextDocumentEdit, lsp.CreateFile, lsp.RenameFile,
-                    lsp.DeleteFile>>>.t2(changes));
+                Either4<lsp.CreateFile, lsp.DeleteFile, lsp.RenameFile,
+                    lsp.TextDocumentEdit>>,
+            List<lsp.TextDocumentEdit>>.t1(changes));
   } else {
     return lsp.WorkspaceEdit(changes: toWorkspaceEditChanges(edits));
   }

pkg/analysis_server/lib/src/lsp/server_capabilities_computer.dart

@@ -167,7 +167,7 @@ class ServerCapabilitiesComputer {
     return ServerCapabilities(
       textDocumentSync: dynamicRegistrations.textSync
           ? null
-          : Either2<TextDocumentSyncOptions, TextDocumentSyncKind>.t1(
+          : Either2<TextDocumentSyncKind, TextDocumentSyncOptions>.t2(
               TextDocumentSyncOptions(
               // The open/close and sync kind flags are registered dynamically if the
               // client supports them, so these static registrations are based on whether
@@ -279,7 +279,7 @@ class ServerCapabilitiesComputer {
       workspace: ServerCapabilitiesWorkspace(
         workspaceFolders: WorkspaceFoldersServerCapabilities(
           supported: true,
-          changeNotifications: Either2<String, bool>.t2(true),
+          changeNotifications: Either2<bool, String>.t1(true),
         ),
         fileOperations: dynamicRegistrations.fileOperations
             ? null

pkg/analysis_server/test/lsp/code_actions_assists_test.dart

@@ -390,8 +390,8 @@ class AssistsCodeActionsTest extends AbstractCodeActionsTest {
     final textEdits = _extractTextDocumentEdits(edit.documentChanges!)
         .expand((tde) => tde.edits)
         .map((edit) => edit.map(
-              (e) => e,
               (e) => throw 'Expected SnippetTextEdit, got AnnotatedTextEdit',
+              (e) => e,
               (e) => throw 'Expected SnippetTextEdit, got TextEdit',
             ))
         .toList();
@@ -535,8 +535,8 @@ void f() {
     final textEdits = _extractTextDocumentEdits(edit.documentChanges!)
         .expand((tde) => tde.edits)
         .map((edit) => edit.map(
-              (e) => e,
               (e) => throw 'Expected SnippetTextEdit, got AnnotatedTextEdit',
+              (e) => e,
               (e) => throw 'Expected SnippetTextEdit, got TextEdit',
             ))
         .toList();
@@ -546,26 +546,26 @@ void f() {
 
   List<TextDocumentEdit> _extractTextDocumentEdits(
           Either2<
-                  List<TextDocumentEdit>,
                   List<
-                      Either4<TextDocumentEdit, CreateFile, RenameFile,
-                          DeleteFile>>>
+                      Either4<CreateFile, DeleteFile, RenameFile,
+                          TextDocumentEdit>>,
+                  List<TextDocumentEdit>>
               documentChanges) =>
       documentChanges.map(
-        // Already TextDocumentEdits
-        (edits) => edits,
         // Extract TextDocumentEdits from union of resource changes
         (changes) => changes
             .map(
               (change) => change.map(
-                (textDocEdit) => textDocEdit,
                 (create) => null,
-                (rename) => null,
                 (delete) => null,
+                (rename) => null,
+                (textDocEdit) => textDocEdit,
               ),
             )
             .whereNotNull()
             .toList(),
+        // Already TextDocumentEdits
+        (edits) => edits,
       );
 }
 

pkg/analysis_server/test/lsp/hover_test.dart

@@ -350,15 +350,15 @@ Type: `String`
 
   MarkupContent _getMarkupContents(Hover hover) {
     return hover.contents.map(
-      (t1) => throw 'Hover contents were String, not MarkupContent',
-      (t2) => t2,
+      (t1) => t1,
+      (t2) => throw 'Hover contents were String, not MarkupContent',
     );
   }
 
   String _getStringContents(Hover hover) {
     return hover.contents.map(
-      (t1) => t1,
-      (t2) => throw 'Hover contents were MarkupContent, not String',
+      (t1) => throw 'Hover contents were MarkupContent, not String',
+      (t2) => t2,
     );
   }
 }

pkg/analysis_server/test/lsp/initialization_test.dart

@@ -320,12 +320,12 @@ class InitializationTest extends AbstractLspAnalysisServerTest {
     // request text document open/close and incremental updates.
     expect(initResult.capabilities.textDocumentSync, isNotNull);
     initResult.capabilities.textDocumentSync!.map(
+      (_) =>
+          throw 'Expected textDocumentSync capabilities to be a TextDocumentSyncOptions',
       (options) {
         expect(options.openClose, isTrue);
         expect(options.change, equals(TextDocumentSyncKind.Incremental));
       },
-      (_) =>
-          throw 'Expected textDocumentSync capabilities to be a $TextDocumentSyncOptions',
     );
     expect(initResult.capabilities.completionProvider, isNotNull);
     expect(initResult.capabilities.hoverProvider, isNotNull);
@@ -696,13 +696,13 @@ class InitializationTest extends AbstractLspAnalysisServerTest {
     // Check some basic capabilities that are unlikely to change.
     expect(result.capabilities.textDocumentSync, isNotNull);
     result.capabilities.textDocumentSync!.map(
+      (_) =>
+          throw 'Expected textDocumentSync capabilities to be a TextDocumentSyncOptions',
       (options) {
         // We'll always request open/closed notifications and incremental updates.
         expect(options.openClose, isTrue);
         expect(options.change, equals(TextDocumentSyncKind.Incremental));
       },
-      (_) =>
-          throw 'Expected textDocumentSync capabilities to be a $TextDocumentSyncOptions',
     );
   }
 

pkg/analysis_server/test/lsp/server_abstract.dart

@@ -684,8 +684,8 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
 
   void applyDocumentChanges(
     Map<String, String> fileContents,
-    Either2<List<TextDocumentEdit>,
-            List<Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>>>
+    Either2<List<Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>>,
+            List<TextDocumentEdit>>
         documentChanges, {
     Map<String, int>? expectedVersions,
   }) {
@@ -695,21 +695,21 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
       expectDocumentVersions(documentChanges, expectedVersions);
     }
     documentChanges.map(
-      (edits) => applyTextDocumentEdits(fileContents, edits),
       (changes) => applyResourceChanges(fileContents, changes),
+      (edits) => applyTextDocumentEdits(fileContents, edits),
     );
   }
 
   void applyResourceChanges(
     Map<String, String> oldFileContent,
-    List<Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>> changes,
+    List<Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>> changes,
   ) {
     for (final change in changes) {
       change.map(
-        (textDocEdit) => applyTextDocumentEdits(oldFileContent, [textDocEdit]),
         (create) => applyResourceCreate(oldFileContent, create),
-        (rename) => applyResourceRename(oldFileContent, rename),
         (delete) => throw 'applyResourceChanges:Delete not currently supported',
+        (rename) => applyResourceRename(oldFileContent, rename),
+        (textDocEdit) => applyTextDocumentEdits(oldFileContent, [textDocEdit]),
       );
     }
   }
@@ -751,7 +751,7 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
   }
 
   String applyTextEdit(String content,
-      Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit> change) {
+      Either3<AnnotatedTextEdit, SnippetTextEdit, TextEdit> change) {
     // Both sites of the union can cast to TextEdit.
     final edit = change.map((e) => e, (e) => e, (e) => e);
     final startPos = edit.range.start;
@@ -815,7 +815,7 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
 
     for (final change in sortedChanges) {
       newContent = applyTextEdit(newContent,
-          Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>.t3(change));
+          Either3<AnnotatedTextEdit, SnippetTextEdit, TextEdit>.t3(change));
     }
 
     return newContent;
@@ -904,30 +904,30 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
   /// Validates the document versions for a set of edits match the versions in
   /// the supplied map.
   void expectDocumentVersions(
-    Either2<List<TextDocumentEdit>,
-            List<Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>>>
+    Either2<List<Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>>,
+            List<TextDocumentEdit>>
         documentChanges,
     Map<String, int> expectedVersions,
   ) {
     documentChanges.map(
-      // Validate versions on simple doc edits
-      (edits) {
-        for (var edit in edits) {
-          expectDocumentVersion(edit, expectedVersions);
-        }
-      },
       // For resource changes, we only need to validate changes since
       // creates/renames/deletes do not supply versions.
       (changes) {
         for (var change in changes) {
           change.map(
-            (edit) => expectDocumentVersion(edit, expectedVersions),
             (create) => {},
-            (rename) {},
             (delete) {},
+            (rename) {},
+            (edit) => expectDocumentVersion(edit, expectedVersions),
           );
         }
       },
+      // Validate versions on simple doc edits
+      (edits) {
+        for (var edit in edits) {
+          expectDocumentVersion(edit, expectedVersions);
+        }
+      },
     );
   }
 
@@ -1783,22 +1783,22 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
   }
 
   /// Creates a [TextEdit] using the `insert` range of a [InsertReplaceEdit].
-  TextEdit textEditForInsert(Either2<TextEdit, InsertReplaceEdit> edit) =>
+  TextEdit textEditForInsert(Either2<InsertReplaceEdit, TextEdit> edit) =>
       edit.map(
-        (_) => throw 'Expected InsertReplaceEdit, got TextEdit',
         (e) => TextEdit(range: e.insert, newText: e.newText),
+        (_) => throw 'Expected InsertReplaceEdit, got TextEdit',
       );
 
   /// Creates a [TextEdit] using the `replace` range of a [InsertReplaceEdit].
-  TextEdit textEditForReplace(Either2<TextEdit, InsertReplaceEdit> edit) =>
+  TextEdit textEditForReplace(Either2<InsertReplaceEdit, TextEdit> edit) =>
       edit.map(
-        (_) => throw 'Expected InsertReplaceEdit, got TextEdit',
         (e) => TextEdit(range: e.replace, newText: e.newText),
+        (_) => throw 'Expected InsertReplaceEdit, got TextEdit',
       );
 
-  TextEdit toTextEdit(Either2<TextEdit, InsertReplaceEdit> edit) => edit.map(
-        (e) => e,
+  TextEdit toTextEdit(Either2<InsertReplaceEdit, TextEdit> edit) => edit.map(
         (_) => throw 'Expected TextEdit, got InsertReplaceEdit',
+        (e) => e,
       );
 
   WorkspaceFolder toWorkspaceFolder(Uri uri) {

pkg/analysis_server/test/tool/lsp_spec/dart_test.dart

@@ -19,7 +19,7 @@ void main() {
 
     test('handles union types', () {
       expect(_union(['string', 'int']).dartTypeWithTypeArgs,
-          equals('Either2<String, int>'));
+          equals('Either2<int, String>'));
     });
 
     test('handles arrays', () {

pkg/analysis_server/test/tool/lsp_spec/generated_classes_test.dart

@@ -72,11 +72,11 @@ void main() {
     test('with union fields can be checked for equality', () {
       final a = SignatureInformation(
           label: 'a',
-          documentation: Either2<String, MarkupContent>.t1('a'),
+          documentation: Either2<MarkupContent, String>.t2('a'),
           parameters: []);
       final b = SignatureInformation(
           label: 'a',
-          documentation: Either2<String, MarkupContent>.t1('a'),
+          documentation: Either2<MarkupContent, String>.t2('a'),
           parameters: []);
 
       expect(a, equals(b));

pkg/analysis_server/test/tool/lsp_spec/json_test.dart

@@ -298,7 +298,7 @@ void main() {
       expect(
           reporter.errors.first,
           equals(
-              'params.documentChanges must be of type Either2<List<TextDocumentEdit>, List<Either4<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>>>'));
+              'params.documentChanges must be of type Either2<List<Either4<CreateFile, DeleteFile, RenameFile, TextDocumentEdit>>, List<TextDocumentEdit>>'));
     });
 
     test('ResponseMessage can include a null result', () {

pkg/analysis_server/test/tool/lsp_spec/typescript_test.dart

@@ -356,8 +356,8 @@ interface SomeInformation {
       expect(field.type, const TypeMatcher<UnionType>());
       final union = field.type as UnionType;
       expect(union.types, hasLength(2));
-      expect(union.types[0], isSimpleType('string'));
-      expect(union.types[1], isArrayOf(isSimpleType('number')));
+      expect(union.types[0], isArrayOf(isSimpleType('number')));
+      expect(union.types[1], isSimpleType('string'));
     });
 
     test('parses an union including Object into a single type', () {

pkg/analysis_server/tool/lsp_spec/typescript_parser.dart

@@ -5,6 +5,7 @@
 import 'dart:math';
 
 import 'package:analysis_server/src/utilities/strings.dart' show capitalize;
+import 'package:collection/collection.dart';
 
 import 'codegen_dart.dart';
 import 'typescript.dart';
@@ -1011,7 +1012,11 @@ abstract class TypeBase {
 class UnionType extends TypeBase {
   final List<TypeBase> types;
 
-  UnionType(this.types);
+  UnionType(this.types) {
+    // Ensure types are always sorted alphabetically to simplify sharing code
+    // because `Either2<A, B>` and `Either2<B, A>` are not the same.
+    types.sortBy((type) => type.dartTypeWithTypeArgs.toLowerCase());
+  }
 
   @override
   String get dartType {