Test that the target node is a SimpleIdentifier.

pkg/analysis_server/lib/src/services/correction/fix_internal.dart

Index: pkg/analysis_server/lib/src/services/correction/fix_internal.dart
diff --git a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
index 0ff70e6780fa60b6437482d7759b815884533100..64fb1d6d92e4f0ae02c78c61ad5a4f7454740fc4 100644
--- a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
+++ b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
@@ -675,6 +675,9 @@ class FixProcessor {
   }
 
   void _addFix_createField() {
+    if (node is! SimpleIdentifier) {
+      return;
+    }
     SimpleIdentifier nameNode = node;
     String name = nameNode.name;
     // prepare target Expression
@@ -802,6 +805,9 @@ class FixProcessor {
   }
 
   void _addFix_createGetter() {
+    if (node is! SimpleIdentifier) {
+      return;
+    }
     SimpleIdentifier nameNode = node;
     String name = nameNode.name;
     if (!nameNode.inGetterContext()) {
@@ -902,6 +908,9 @@ class FixProcessor {
   }
 
   void _addFix_createLocalVariable() {
+    if (node is! SimpleIdentifier) {
+      return;
+    }
     SimpleIdentifier nameNode = node;
     String name = nameNode.name;
     // if variable is assigned, convert assignment into declaration