PictureStream();

../../.pub-cache/hosted/pub.flutter-io.cn/flutter_svg-0.14.4/lib/src/picture_stream.dart:92:3: Error: The superclass, 'Diagnosticable', has no unnamed constructor that takes no arguments.
PictureStream();
^^^^^^^^^^^^^
../../.pub-cache/hosted/pub.flutter-io.cn/flutter_svg-0.14.4/lib/src/picture_stream.dart:192:16: Error: The superclass, 'Diagnosticable', has no unnamed constructor that takes no arguments.
abstract class PictureStreamCompleter extends Diagnosticable {
^

FAILURE: Build failed with an exception.

• Where:
  Script '**flutter/packages/flutter_tools/gradle/flutter.gradle' line: 896

• What went wrong:
  Execution failed for task ':app:compileFlutterBuildDebug'.

Process 'command '**/flutter/bin/flutter'' finished with non-zero exit value 1

• Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

• Get more help at https://help.gradle.org

解决办法

flutter pub upgrade