object.cc: 16408: error: unreachable code when calling _typeOf<Provider<S>>() #32942

kgberry83 · 2018-04-22T13:39:15Z

This code does not fail on startup, but during hot reload.

Flutter version
Flutter 0.3.0 • channel dev • https://github.com/flutter/flutter.git
Framework • revision c73b8a7cf6 (7 days ago) • 2018-04-12 16:17:26 -0700
Engine • revision 8a6e64a8ef
Tools • Dart 2.0.0-dev.47.0.flutter-4126459025

Repro code

//-------------------------------------------------------------------
import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  final String title;

  MyApp({Key key, this.title}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "Flutter Redux Demo",
      theme: ThemeData(
        primarySwatch: Colors.red,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class AppState {

}

class Provider<T> {

}

abstract class PageState<W extends StatefulWidget, S> extends State<W> {
  // Workaround to capture generics
  static Type _typeOf<T>() => T;

  void init() {
    final type1 = _typeOf<Provider<AppState>>(); // works
    final type2 = _typeOf<Provider<S>>(); // DOES NOT WORK - object.cc: 16408: error: unreachable code
  }
}

class MyHomePage extends StatefulWidget {
  final String title;
  MyHomePage({Key key, this.title}) : super(key: key);

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends PageState<MyHomePage, AppState> {
  @override
  Widget build(BuildContext context) {
    super.init(); // calls into method that causes failure

    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(

        ),
      ),
    );
  }
}

Log Failure:
Initializing hot reload...
E/DartVM ( 3758): ../../third_party/dart/runtime/vm/object.cc: 16408: error: unreachable code
E/DartVM ( 3758): Dumping native stack trace for thread ec6
E/DartVM ( 3758): [0x0000736d9c49df67] Unknown symbol
E/DartVM ( 3758): [0x0000736d9c49df67] Unknown symbol
E/DartVM ( 3758): [0x0000736d9c739786] Unknown symbol
E/DartVM ( 3758): -- End of DumpStackTrace
F/libc ( 3758): Fatal signal 6 (SIGABRT), code -6 in tid 3782 (Thread-2)

Build fingerprint: 'Android/sdk_google_phone_x86_64/generic_x86_64:7.0/NYC/4662066:userdebug/dev-keys'
Revision: '0'
ABI: 'x86_64'
pid: 3758, tid: 3782, name: Thread-2 >>> com.example.helloworld <<<
signal 6 (SIGABRT), code -6 (SI_TKILL), fault addr --------
rax 0000000000000000 rbx 0000736d9b5654f8 rcx ffffffffffffffff rdx 0000000000000006
rsi 0000000000000ec6 rdi 0000000000000eae
r8 0000000000000000 r9 000000000000001f r10 0000000000000008 r11 0000000000000202
r12 0000000000000ec6 r13 0000000000000006 r14 0000736d9c7a2837 r15 0000736d9b55dbd0
cs 0000000000000033 ss 000000000000002b
rip 0000736db7c93b67 rbp 0000000000000000 rsp 0000736d9b55da38 eflags 0000000000000202
backtrace:
#00 pc 000000000008db67 /system/lib64/libc.so (tgkill+7)
#1 pc 000000000008a601 /system/lib64/libc.so (pthread_kill+65)
#2 pc 0000000000030241 /system/lib64/libc.so (raise+17)
#3 pc 000000000002877d /system/lib64/libc.so (abort+77)
#4 pc 000000000078c695 /data/app/com.example.helloworld-1/lib/x86_64/libflutter.so
#5 pc 0000000000a8078a /data/app/com.example.helloworld-1/lib/x86_64/libflutter.so
#6 pc 0000000000750ed2 /data/app/com.example.helloworld-1/lib/x86_64/libflutter.so
#7 pc 0000000000704cf6 /data/app/com.example.helloworld-1/lib/x86_64/libflutter.so
#8 pc 000000000071e48f /data/app/com.example.helloworld-1/lib/x86_64/libflutter.so
#9 pc 000000000082ea2c /data/app/com.example.helloworld-1/lib/x86_64/libflutter.so
#10 pc 000000000000063a anonymous:0000736d98940000
#11 pc 0000000000020fa0 anonymous:0000736d8f580000
#12 pc 0000000000020840 anonymous:0000736d8f580000
#13 pc 0000000000002233 anonymous:0000736d8de00000
#14 pc 0000000000008523 anonymous:0000736d8e100000
#15 pc 000000000000768c anonymous:0000736d8e100000
#16 pc 0000000000006f98 anonymous:0000736d8e100000
#17 pc 000000000003f2c6 anonymous:0000736d8e100000
#18 pc 000000000000687f anonymous:0000736d8e100000
#19 pc 00000000000054b2 anonymous:0000736d8e100000
#20 pc 00000000000046af anonymous:0000736d8e100000
#21 pc 000000000000887b anonymous:0000736d8e100000
#22 pc 000000000000768c anonymous:0000736d8e100000
#23 pc 0000000000006f98 anonymous:0000736d8e100000
#24 pc 000000000000687f anonymous:0000736d8e100000
#25 pc 00000000000054b2 anonymous:0000736d8e100000
#26 pc 00000000000046af anonymous:0000736d8e100000
#27 pc 0000000000031077 anonymous:0000736d8db80000
#28 pc 00000000000054b2 anonymous:0000736d8e100000
#29 pc 00000000000046af anonymous:0000736d8e100000
#30 pc 0000000000031077 anonymous:0000736d8db80000
#31 pc 00000000000054b2 anonymous:0000736d8e100000
#32 pc 00000000000046af anonymous:0000736d8e100000
#33 pc 0000000000031077 anonymous:0000736d8db80000
#34 pc 00000000000054b2 anonymous:0000736d8e100000
#35 pc 00000000000046af anonymous:0000736d8e100000
#36 pc 0000000000031077 anonymous:0000736d8db80000
#37 pc 00000000000054b2 anonymous:0000736d8e100000
#38 pc 00000000000046af anonymous:0000736d8e100000
#39 pc 000000000000887b anonymous:0000736d8e100000
#40 pc 000000000000768c anonymous:0000736d8e100000
#41 pc 0000000000006f98 anonymous:0000736d8e100000
#42 pc 000000000003f2c6 anonymous:0000736d8e100000
#43 pc 000000000000687f anonymous:0000736d8e100000
#44 pc 00000000000054b2 anonymous:0000736d8e100000
#45 pc 00000000000046af anonymous:0000736d8e100000
#46 pc 000000000000887b anonymous:0000736d8e100000
#47 pc 000000000000768c anonymous:0000736d8e100000
#48 pc 0000000000006f98 anonymous:0000736d8e100000
#49 pc 000000000000687f anonymous:0000736d8e100000
#50 pc 00000000000054b2 anonymous:0000736d8e100000
#51 pc 00000000000046af anonymous:0000736d8e100000
#52 pc 000000000000887b anonymous:0000736d8e100000
#53 pc 000000000000768c anonymous:0000736d8e100000
#54 pc 0000000000006f98 anonymous:0000736d8e100000
#55 pc 000000000003f2c6 anonymous:0000736d8e100000
#56 pc 000000000000687f anonymous:0000736d8e100000
#57 pc 00000000000054b2 anonymous:0000736d8e100000
#58 pc 00000000000046af anonymous:0000736d8e100000
#59 pc 0000000000031077 anonymous:0000736d8db80000
#60 pc 00000000000054b2 anonymous:0000736d8e100000
#61 pc 00000000000046af anonymous:0000736d8e100000
#62 pc 000000000000887b anonymous:0000736d8e100000
#63 pc 000000000000768c anonymous:0000736d8e100000
Lost connection to device.

The text was updated successfully, but these errors were encountered:

dgrove · 2018-04-22T16:13:59Z

Tentatively targeting beta4

aam · 2018-05-07T17:19:43Z

I am not able to reproduce this right away - hot reload seems to be working fine as I am making changes to 'Flutter Redux Demo' and 'Flutter Demo Home Page' string literals in the code sample above.

 $FH/flutter/bin/flutter doctor
[✓] Flutter (Channel master, v0.3.6-pre.113, on Linux, locale en_US.UTF-8)
    • Flutter version 0.3.6-pre.113 at $FH/flutter
    • Framework revision d820e5f3b1 (4 days ago), 2018-05-03 22:27:29 -0700
    • Engine revision e976be13c5
    • Dart version 2.0.0-dev.53.0.flutter-e6d7d67f4b

@affinnen can you share more details what you change when the hot reload fails for you?

kgberry83 · 2018-05-07T21:19:14Z

Try changing the theme color.

aam · 2018-05-07T21:24:36Z

Hot reloading while changing primarySwatch: Colors.red to primarySwatch: Colors.blue also works.
What device did you run this on? I'm running on Android Nexus4, with flutter dev running on Linux host.

kgberry83 · 2018-05-08T00:53:23Z

@aam, here are the exact repro steps.

Start Simulator iPhone 6 - 11.2
Create a new app from Visual Studio Code - hello_world
Start Debugging (you may have to set your debug configuration)
Finally, paste the code example I provided above and Save.
Hot reload should trigger and you will get the exception.

Visual Studio Code: Version 1.22.2
Mac OS: 10.13.4
Flutter 0.3.5 • channel dev • https://github.com/flutter/flutter.git
Framework • revision 7ffcd3d22d (13 days ago) • 2018-04-24 14:03:41 -0700
Engine • revision ec611470b5
Tools • Dart 2.0.0-dev.48.0.flutter-fe606f890b

../../third_party/dart/runtime/vm/object.cc: 16463: error: unreachable code
Dumping native stack trace for thread 5507
[0x000000010b18cc67] dart::Profiler::DumpStackTrace(bool)
[0x000000010b18cc67] dart::Profiler::DumpStackTrace(bool)
[0x000000010b44d6e0] dart::DynamicAssertionHelper::Fail(char const*, ...)
[0x000000010b0f6b64] dart::AbstractType::Canonicalize(dart::ZoneGrowableHandlePtrArray<dart::AbstractType const>*) const
[0x000000010b0a86fa] dart::TypeArguments::Canonicalize(dart::ZoneGrowableHandlePtrArray<dart::AbstractType const>*) const
[0x000000010b0fb6f0] dart::Type::Canonicalize(dart::ZoneGrowableHandlePtrArray<dart::AbstractType const>*) const
[0x000000010b0a86fa] dart::TypeArguments::Canonicalize(dart::ZoneGrowableHandlePtrArray<dart::AbstractType const>*) const
[0x000000010b0c2136] dart::TypeArguments::InstantiateAndCanonicalizeFrom(dart::TypeArguments const&, dart::TypeArguments const&, dart::Error*) const
[0x000000010b1dfdc0] dart::DRT_InstantiateTypeArguments(dart::NativeArguments)
[0x000000011e84063b] [Stub] CallToRuntime
[0x000000012557985c] PageState.init
[0x00000001255795f8] _MyHomePageState.build
[0x0000000124cf04b4] StatefulElement.build
[0x0000000124ab7e64] ComponentElement.performRebuild
[0x0000000124ab700d] Element.rebuild
[0x0000000125542369] StatefulElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000125544e65] SingleChildRenderObjectElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000124ab81bc] ComponentElement.performRebuild
[0x0000000124ab700d] Element.rebuild
[0x0000000125544b57] StatelessElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000125544e65] SingleChildRenderObjectElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000125544e65] SingleChildRenderObjectElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x000000012555513b] RenderObjectElement.updateChildren
[0x0000000125552bdc] MultiChildRenderObjectElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000124ab81bc] ComponentElement.performRebuild
[0x0000000124ab700d] Element.rebuild
[0x0000000125542369] StatefulElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000125544e65] SingleChildRenderObjectElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000124ab81bc] ComponentElement.performRebuild
[0x0000000124ab700d] Element.rebuild
[0x0000000125542369] StatefulElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000125544e65] SingleChildRenderObjectElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000124ab81bc] ComponentElement.performRebuild
[0x0000000124ab700d] Element.rebuild
[0x0000000125542369] StatefulElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000125544e65] SingleChildRenderObjectElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000124ab81bc] ComponentElement.performRebuild
[0x0000000124ab700d] Element.rebuild
[0x0000000125542369] StatefulElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000124ab81bc] ComponentElement.performRebuild
[0x0000000124ab700d] Element.rebuild
[0x0000000125544b57] StatelessElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000124ab81bc] ComponentElement.performRebuild
[0x0000000124ab700d] Element.rebuild
[0x0000000125542369] StatefulElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000125544e65] SingleChildRenderObjectElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000124ab81bc] ComponentElement.performRebuild
[0x0000000124ab700d] Element.rebuild
[0x0000000125540468] ProxyElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000125544e65] SingleChildRenderObjectElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000124ab81bc] ComponentElement.performRebuild
[0x0000000124ab700d] Element.rebuild
[0x0000000125542369] StatefulElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000124ab81bc] ComponentElement.performRebuild
[0x0000000124ab700d] Element.rebuild
[0x0000000125544b57] StatelessElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000125544e65] SingleChildRenderObjectElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000124ab81bc] ComponentElement.performRebuild
[0x0000000124ab700d] Element.rebuild
[0x0000000125540468] ProxyElement.update
[0x0000000124ab3ce5] Element.updateChild
[0x0000000124ab81bc] ComponentElement.performRebuild
[0x0000000124ab700d] Element.rebuild
[0x0000000124aaa7dc] BuildOwner.buildScope
[0x0000000125ae7db6] _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&RendererBinding&WidgetsBinding.drawFrame
[0x000000012539dd45] _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&RendererBinding._handlePersistentFrameCallback
[0x000000012539e4df] _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&RendererBinding._handlePersistentFrameCallback
[0x00000001211a6955] _Closure.call
[0x0000000125ae7596] _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback
[0x0000000125ae6708] _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame
[0x00000001253ac12b] _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.scheduleWarmUpFrame.<anonymous closure>
[0x0000000121180772] _Closure.call
[0x0000000125ae3bea] Timer._createTimer.<anonymous closure>
[0x00000001211a6955] _Closure.call
[0x0000000125ae2cf5] _Timer._runTimers
[0x0000000125ae0f6f] _Timer._handleMessage
[0x0000000125ae0a7b] _Timer._handleMessage
[0x00000001211a6955] _Closure.call
[0x00000001211a685c] _RawReceivePortImpl._handleMessage
[0x000000011e840a83] [Stub] InvokeDartCode
[0x000000010b03df66] dart::DartEntry::InvokeFunction(dart::Function const&, dart::Array const&, dart::Array const&, unsigned long)
[0x000000010b04167e] dart::DartLibraryCalls::HandleMessage(dart::Object const&, dart::Instance const&)
[0x000000010b06c4bd] dart::IsolateMessageHandler::HandleMessage(dart::Message*)
[0x000000010b09590e] dart::MessageHandler::HandleMessages(dart::MonitorLocker*, bool, bool)
[0x000000010b095a10] dart::MessageHandler::HandleNextMessage()
[0x000000010b38669d] Dart_HandleMessage
[0x000000010aec6509] tonic::DartMessageHandler::OnHandleMessage(tonic::DartState*)
[0x000000010ab0fdd6] fml::MessageLoopImpl::RunExpiredTasks()
[0x000000010ab12abc] fml::MessageLoopDarwin::OnTimerFire(__CFRunLoopTimer*, fml::MessageLoopDarwin*)
[0x000000010a521174] __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__
[0x000000010a520e32] __CFRunLoopDoTimer
[0x000000010a5209ea] __CFRunLoopDoTimers
[0x000000010a518404] __CFRunLoopRun
[0x000000010a517889] CFRunLoopRunSpecific
[0x000000010ab12c0d] fml::MessageLoopDarwin::Run()
[0x000000010ab0ff0d] fml::MessageLoopImpl::DoRun()
[0x000000010ab12612] std::__1::__thread_proxy<std::__1::tuple<std::__1::unique_ptr<std::__1::__thread_struct, std::__1::default_delete<std::__1::__thread_struct> >, fml::Thread::Thread(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)::$_0> >(void*, void*)
[0x00000001122aa661] _pthread_body
[0x00000001122aa50d] _pthread_body
[0x00000001122a9bf9] thread_start
-- End of DumpStackTrace
Lost connection to device.
Exited (sigterm)

a-siva · 2018-05-08T01:06:10Z

/cc @crelier

aam · 2018-05-08T16:26:42Z

Can't repro this on iOS simulator on mac neither.
Can you try flutter master channel?
Can you try running your app from command line(flutter run -v, then 'r' to hot reload)?

aam · 2018-05-08T16:46:07Z

@affinnen wrote:

Create a new app from Visual Studio Code - hello_world

Start Debugging (you may have to set your debug configuration)

Finally, paste the code example I provided above and Save.

Can you please clarify whether it crashes for you only when you replace complete hello_world app with your sample and do hot reload, while hot reload works fine if you start from your sample and hot reload incremental change(like changing primarySwatch color)

aam · 2018-05-08T17:53:03Z

Here is the stacktrace with line numbers

E/DartVM  (27829): ../../third_party/dart/runtime/vm/object.cc: 16493: error: unreachable code
E/DartVM  (27829): Dumping native stack trace for thread 6cce
E/DartVM  (27829):   [0xa3af498d] Unknown symbol
E/DartVM  (27829):   [0xa3af498d] Unknown symbol
E/DartVM  (27829):   [0xa3db4341] Unknown symbol
E/DartVM  (27829):   [0xa3a850e5] Unknown symbol
E/DartVM  (27829):   [0xa3a41835] Unknown symbol
E/DartVM  (27829):   [0xa3a89271] Unknown symbol
E/DartVM  (27829):   [0xa3a41835] Unknown symbol
E/DartVM  (27829):   [0xa3a574c3] Unknown symbol
E/DartVM  (27829):   [0xa3b32b45] Unknown symbol
E/DartVM  (27829): -- End of DumpStackTrace
F/libc    (27829): Fatal signal 6 (SIGABRT), code -6 in tid 27854 (Thread-579)
I/DEBUG   (  188): *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
I/DEBUG   (  188): Build fingerprint: 'google/occam/mako:5.1.1/LMP/2348323:userdebug/dev-keys'
I/DEBUG   (  188): Revision: '11'
I/DEBUG   (  188): ABI: 'arm'
I/DEBUG   (  188): pid: 27829, tid: 27854, name: Thread-579  >>> com.yourcompany.sample <<<
I/DEBUG   (  188): signal 6 (SIGABRT), code -6 (SI_TKILL), fault addr --------
I/DEBUG   (  188):     r0 00000000  r1 00006cce  r2 00000006  r3 00000000
I/DEBUG   (  188):     r4 afa29dd8  r5 00000006  r6 0000000b  r7 0000010c
I/DEBUG   (  188):     r8 afa27fb8  r9 afa27fb4  sl 00000002  fp 00000000
I/DEBUG   (  188):     ip 00006cce  sp afa277b8  lr b6dbe989  pc b6de3fe4  cpsr 600f0010
I/DEBUG   (  188): 
I/DEBUG   (  188): backtrace:
I/DEBUG   (  188):     #00 pc 0003bfe4  /system/lib/libc.so (tgkill+12)
I/DEBUG   (  188):     #01 pc 00016985  /system/lib/libc.so (pthread_kill+52)
I/DEBUG   (  188):     #02 pc 00017597  /system/lib/libc.so (raise+10)
I/DEBUG   (  188):     #03 pc 00013d3d  /system/lib/libc.so (__libc_android_abort+36)
I/DEBUG   (  188):     #04 pc 000124ec  /system/lib/libc.so (abort+4)
I/DEBUG   (  188):     #05 pc 003e5567  /data/app/com.yourcompany.sample-2/lib/arm/libflutter.so
I/DEBUG   (  188):     #06 pc 01007343  /data/app/com.yourcompany.sample-2/lib/arm/libflutter.so
I/DEBUG   (  188):     #07 pc 00cd80e1  /data/app/com.yourcompany.sample-2/lib/arm/libflutter.so
I/DEBUG   (  188):     #08 pc 00c94833  /data/app/com.yourcompany.sample-2/lib/arm/libflutter.so
I/DEBUG   (  188):     #09 pc 00cdc26d  /data/app/com.yourcompany.sample-2/lib/arm/libflutter.so
I/DEBUG   (  188):     #10 pc 00c94833  /data/app/com.yourcompany.sample-2/lib/arm/libflutter.so
I/DEBUG   (  188):     #11 pc 00caa4bf  /data/app/com.yourcompany.sample-2/lib/arm/libflutter.so
I/DEBUG   (  188):     #12 pc 00d85b41  /data/app/com.yourcompany.sample-2/lib/arm/libflutter.so
I/DEBUG   (  188):     #13 pc 0000031c  <unknown>
I/DEBUG   (  188):

../../third_party/skia/src/ports/SkMemory_malloc.cpp:41
../../third_party/dart/runtime/platform/assert.cc:43
../../third_party/dart/runtime/vm/object.cc:16493
../../third_party/dart/runtime/vm/object.cc:5425
../../third_party/dart/runtime/vm/object.cc:17809
../../third_party/dart/runtime/vm/object.cc:5425
../../third_party/dart/runtime/vm/object.cc:5301
../../third_party/dart/runtime/vm/runtime_entry.cc:376

crelier · 2018-05-08T17:59:49Z

Since we are having trouble reproducing this, I could add some defensive code to prevent this from happening. Hot reload is brittle anyway, so more robust coding cannot hurt. I cannot guarantee it would not crash later, though.

From the stack trace above, I see that a type argument vector is being canonicalized, and a type argument in the vector is null. This can happen for recursive types, when they are not yet finalized. But this should not happen at runtime. This is probably an issue with hot reload, but until we can reproduce it, I do not know why this is happening.

The fix would be to guard these lines in object.cc against a null type argument:

RawTypeArguments* TypeArguments::Canonicalize(TrailPtr trail) const {
  [...]
  if (result.IsNull()) {
    // Canonicalize each type argument.
    AbstractType& type_arg = AbstractType::Handle(zone);
    for (intptr_t i = 0; i < num_types; i++) {
      type_arg = TypeAt(i);
      if (!type_arg.IsNull()) {   // <<<<<< ADD THIS LINE
        type_arg = type_arg.Canonicalize(trail);
        if (IsCanonical()) {
          // Canonicalizing this type_arg canonicalized this type.
          ASSERT(IsRecursive());
          return this->raw();
        }
        SetTypeAt(i, type_arg);
      }  // <<<<<< ADD THIS LINE
    }
  [...]

What do you think?

aam · 2018-05-08T18:10:52Z

Starting from the app below, then changing three lines marked with //HR will crash VM with the same error.

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  final String title;

  MyApp({Key key, this.title}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "Flutter Redux Demo",
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class AppState {

}

class Provider<T> {

}

abstract class PageState<W extends StatefulWidget, S> extends State<W> {
  // Workaround to capture generics
  static Type _typeOf<T>() => T;

  void init() {
    final type1 = _typeOf<Provider<AppState>>(); // works
    final type2 = _typeOf<Provider<S>>(); // DOES NOT WORK - object.cc: 16408: error: unreachable code
  }
}

class MyHomePage extends StatefulWidget {
  final String title;
  MyHomePage({Key key, this.title}) : super(key: key);

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> { //HR: comment this line
//HR class _MyHomePageState extends PageState<MyHomePage, AppState> {
  @override
  Widget build(BuildContext context) {
    //HR super.init(); // calls into method that causes failure

    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(

        ),
      ),
    );
  }
}

crelier · 2018-05-08T18:39:00Z

Changing the super type of class _MyHomePageState should invalidate all code from this class, including the code for _MyHomePageState.build and its call to super.init().

aam · 2018-05-08T19:31:57Z

Current theory is that hot-reload request should have been rejected because _MyHomePageState class got different number of type parameters(used to be 1, now it is 2). Since it was not rejected, that leads to the crash further down the pipeline.

cc @rmacnak-google

… change. Bug: #32942 Change-Id: I7f10a327a82ddf23a946b1ba98c63c2e7947d99f Reviewed-on: https://dart-review.googlesource.com/54313 Commit-Queue: Alexander Aprelev <aam@google.com> Reviewed-by: Régis Crelier <regis@google.com>

There might be better fix with using canonical types for comparison, we just need to make sure we canonicalize class's type when finalizing it. Bug:#32942 Change-Id: I2301a7cb91146d587893f91f2d6ee7b731ea3c62 Reviewed-on: https://dart-review.googlesource.com/54314 Commit-Queue: Alexander Aprelev <aam@google.com> Reviewed-by: Régis Crelier <regis@google.com>

aam · 2018-05-09T16:37:39Z

Fixed via 2ad715e

kgberry83 mentioned this issue Apr 22, 2018

Dart 2 class generics bug? #32425

Closed

dgrove added this to the Dart2Beta4 milestone Apr 22, 2018

dgrove added the area-vm Use area-vm for VM related issues, including code coverage, FFI, and the AOT and JIT backends. label Apr 22, 2018

dgrove assigned a-siva Apr 22, 2018

dgrove added the crash Process exits with SIGSEGV, SIGABRT, etc. An unhandled exception is not a crash. label Apr 22, 2018

a-siva assigned aam and unassigned a-siva May 3, 2018

a-siva added the P1 A high priority bug; for example, a single project is unusable or has many test failures label May 3, 2018

aam closed this as completed May 9, 2018

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object.cc: 16408: error: unreachable code when calling _typeOf<Provider<S>>() #32942

object.cc: 16408: error: unreachable code when calling _typeOf<Provider<S>>() #32942

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aam commented May 9, 2018

object.cc: 16408: error: unreachable code when calling _typeOf<Provider<S>>() #32942

object.cc: 16408: error: unreachable code when calling _typeOf<Provider<S>>() #32942

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