[analysis_server] Fix hover on enum constant declaration

Fixes https://github.com/dart-lang/sdk/issues/63223

Change-Id: I42c75520ce11932bd1c894783cbfc27ac3c8ebd2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/504260
Reviewed-by: Keerti Parthasarathy <keertip@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Keerti Parthasarathy <keertip@google.com>

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

@@ -47,6 +47,7 @@ class DartUnitHoverComputer {
 
     if (node is CompilationUnitMember ||
         node is CatchClauseParameter ||
+        node is EnumConstantDeclaration ||
         node is Expression ||
         node is FormalParameter ||
         node is MethodDeclaration ||
@@ -232,6 +233,7 @@ class DartUnitHoverComputer {
       ConstructorDeclaration() =>
         node.name ?? node.typeName ?? node.newKeyword ?? node.factoryKeyword,
       DeclaredIdentifier() => node.name,
+      EnumConstantDeclaration() => node.name,
       EnumDeclaration() => node.namePart.typeName,
       Expression() => node,
       ExtensionDeclaration() => node.name,

pkg/analysis_server/test/lsp/hover_test.dart

@@ -450,6 +450,26 @@ Declared in `MyEnum` in *package:test/main.dart*.''';
     await assertStringContents(content, equals(expected));
   }
 
+  Future<void> test_enum_member_declaration() async {
+    var content = '''
+enum E {
+  /// Docs
+  [!on^e!]
+}
+''';
+    var expected = '''
+```dart
+E one
+```
+Type: `E`
+
+Declared in `E` in *package:test/main.dart*.
+
+---
+Docs''';
+    await assertStringContents(content, equals(expected));
+  }
+
   Future<void> test_enum_values() async {
     var content = '''
 enum MyEnum { one }