I get this error if try to create new FirebaseAuth instance after creating GoogleSignIn()
But it works fine if created before GoogleSignIn()

Screenshot

pubspec dependencies

cupertino_icons: ^0.1.0
shared_preferences: ^0.4.1
charts_flutter: ^0.2.0
image_picker: 0.4.1
google_sign_in: 3.0.2
firebase_analytics: 0.3.3
firebase_auth: 0.5.5
firebase_database: 0.4.6
firebase_storage: 0.3.0

Run your application with flutter run and attach all the log output.

flutter analyze errors

error - The class 'FirebaseAuth' doesn't have a constructor named 'instance' at lib\main.dart:34:42 - new_with_undefined_constructor
error - Expected to find '(' at lib\main.dart:34:50 - expected_token

Flutter Doctor

[√] Flutter (Channel master, v0.3.6-pre.50, on Microsoft Windows [Version 10.0.16299.402], locale en-PK)
• Flutter version 0.3.6-pre.50 at C:\fluttersdk\flutter
• Framework revision c813eab (11 hours ago), 2018-04-27 22:55:51 -0700
• Engine revision 613aae0
• Dart version 2.0.0-dev.50.0.flutter-cd0c4e4fe1

[√] Android toolchain - develop for Android devices (Android SDK 27.0.3)
• Android SDK at C:\Users\Muhammad Zeeshan\AppData\Local\Android\sdk
• Android NDK location not configured (optional; useful for native profiling support)
• Platform android-27, build-tools 27.0.3
• Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1024-b02)
• All Android licenses accepted.

[√] Android Studio (version 3.1)
• Android Studio at C:\Program Files\Android\Android Studio
• Flutter plugin version 23.2.2
• Dart plugin version 173.4700
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1024-b02)

[√] VS Code, 64-bit edition (version 1.22.2)
• VS Code at C:\Program Files\Microsoft VS Code
• Dart Code extension version 2.12.0

[√] Connected devices (1 available)
• TRT L21A • VWD7N17706001493 • android-arm • Android 7.0 (API 24)

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