Required params message fix.

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 4234 matching lines @@
       DartType type, ArgumentList argumentList, AstNode node) {
     if (type is FunctionType) {
       List<ParameterElement> parameters = type.parameters;
       for (ParameterElement param in parameters) {
         if (param.parameterKind == ParameterKind.NAMED) {
           ElementAnnotationImpl annotation = _getRequiredAnnotation(param);
           if (annotation != null) {
             String paramName = param.name;
             if (!_containsNamedExpression(argumentList, paramName)) {
               DartObject constantValue = annotation.constantValue;
-              String reason =
-                  constantValue.getField('reason')?.toStringValue() ?? '';
-              _errorReporter.reportErrorForNode(
-                  HintCode.MISSING_REQUIRED_PARAM, node, [paramName, reason]);
+              String reason = constantValue.getField('reason')?.toStringValue();
+              if (reason != null) {
+                _errorReporter.reportErrorForNode(
+                    HintCode.MISSING_REQUIRED_PARAM_WITH_DETAILS,
+                    node,
+                    [paramName, reason]);
+              } else {
+                _errorReporter.reportErrorForNode(
+                    HintCode.MISSING_REQUIRED_PARAM, node, [paramName]);
+              }
             }
           }
         }
       }
     }
   }
 
   /**
    * Verify that the given function [body] does not contain return statements
    * that both have and do not have return values.
@@ skipping 1888 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);
     }
   }
 }