Don't resolve FieldFormalParameter field if not in constructor.

pkg/analyzer/lib/src/generated/error_verifier.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library analyzer.src.generated.error_verifier;
 
 import 'dart:collection';
 import "dart:math" as math;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 5886 matching lines @@
     if (element is ExecutableElement && !element.isStatic) {
       return;
     }
     _errorReporter.reportErrorForNode(
         StaticTypeWarningCode.UNQUALIFIED_REFERENCE_TO_NON_LOCAL_STATIC_MEMBER,
         name,
         [enclosingElement.name]);
   }
 
   void _checkForValidField(FieldFormalParameter parameter) {
+    AstNode parent2 = parameter.parent?.parent;
+    if (parent2 is! ConstructorDeclaration &&
+        parent2?.parent is! ConstructorDeclaration) {
+      return;
+    }
     ParameterElement element = parameter.element;
     if (element is FieldFormalParameterElement) {
       FieldElement fieldElement = element.field;
       if (fieldElement == null || fieldElement.isSynthetic) {
         _errorReporter.reportErrorForNode(
             CompileTimeErrorCode.INITIALIZING_FORMAL_FOR_NON_EXISTENT_FIELD,
             parameter,
             [parameter.identifier.name]);
       } else {
         ParameterElement parameterElement = parameter.element;
@@ skipping 1156 matching lines @@
 class _InvocationCollector extends RecursiveAstVisitor {
   final List<String> superCalls = <String>[];
 
   @override
   visitMethodInvocation(MethodInvocation node) {
     if (node.target is SuperExpression) {
       superCalls.add(node.methodName.name);
     }
   }
 }