[analysis_server] Exclude the enum body semicolon from format-on-type

`EnumBody.semicolon` is the semicolon between the constants and other members. Since the formatter removes this semicolon if there's nothing after it, we can't have it trigger formatting or it will just immediately delete the semicolon you typed.

Fixes #61909
Fixes dart-lang/dart_style#1782
Fixes Dart-Code/Dart-Code#5602

Change-Id: I52bf113b832446da1b672d949d0fc3c2f6d018bf
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/466101
Commit-Queue: Samuel Rawlins <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: DanTup

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

@@ -128,7 +128,6 @@ class FormatOnTypeHandler
         // Bodies
         EmptyClassBody(:var semicolon) ||
         EmptyFunctionBody(:var semicolon) ||
-        EnumBody(:var semicolon?) ||
         ExpressionFunctionBody(:var semicolon?) ||
         NativeFunctionBody(:var semicolon) ||
         // Declarations

pkg/analysis_server/test/lsp/format_test.dart

@@ -253,6 +253,16 @@ void f  ()
     ''', isNull);
   }
 
+  /// Ensure the semicolon after enum constants does not trigger formatting
+  /// because the formatter removes it if there is nothing after it.
+  ///
+  /// https://github.com/dart-lang/sdk/issues/61909
+  Future<void> test_formatOnType_bad_semiColon_enumBodySeparator() async {
+    await expectFormatOnTypeResult('''
+enum E { a, b[!;!] }
+    ''', isNull);
+  }
+
   Future<void> test_formatOnType_bad_semicolon_inComment() async {
     await expectFormatOnTypeResult('''
 void f  ()
@@ -318,6 +328,17 @@ void f  ()
     ''', isNotNull);
   }
 
+  Future<void> test_formatOnType_good_semiColon_enumConstructor() async {
+    await expectFormatOnTypeResult('''
+enum X {
+  a,
+  b;
+
+  const X()[!;!]
+}
+    ''', isNotNull);
+  }
+
   Future<void> test_formatOnType_good_semicolon_statementEnd() async {
     await expectFormatOnTypeResult('''
 void f  ()