我正在尝试新的 dart 3功能，但我的应用程序不会编译。

packages/charts_repository/lib/src/models/peak_mean.dart:35:14: Error: Expected ')' before this.
    if (json case {'DataSavedTime': final date, 'Value': final value}) {
             ^^^^
packages/charts_repository/lib/src/models/peak_mean.dart:36:38: Error: Undefined name 'date'.
      return PeakMean(DateTime.parse(date), num.parse(value));
                                     ^^^^
packages/charts_repository/lib/src/models/peak_mean.dart:36:55: Error: Undefined name 'value'.
      return PeakMean(DateTime.parse(date), num.parse(value));
                                                      ^^^^^
packages/charts_repository/lib/src/models/peak_mean.dart:35:9: Error: A value of type 'Map<String, dynamic>' can't be assigned to a variable of type 'bool'.
 - 'Map' is from 'dart:core'.
    if (json case {'DataSavedTime': final date, 'Value': final value}) {

这里是新的 dart 3功能造成的错误

class PeakMean {
  final DateTime x;
  final num y;

  PeakMean(this.x, this.y);

  factory PeakMean.fromJson(Map<String, dynamic> json) {
    if (json case {'DataSavedTime': final date, 'Value': final value}) {
      return PeakMean(DateTime.parse(date), num.parse(value));
    }
    throw const FormatException('Unexpected JSON format');
  }
}

flutter doctor -v的输出

• Flutter version 3.10.4 on channel stable at C:\Users\itsroom\Development\flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 682aa387cf (3 days ago), 2023-06-05 18:04:56 -0500
    • Engine revision 2a3401c9bb
    • Dart version 3.0.3
    • DevTools version 2.23.1

pubspec.yaml

environment:
  sdk: ">=3.0.0 <4.0.0"