dart fix is failing

[bh-oussama]

When running dart fix . --apply it fails and throws the following exception

Exception while getting bulk fixes: Exception generating fix for specify_nonobvious_local_variable_types in **/project/lib/src/data/async_reference.dart
Stack Overflow
#0      DartEditBuilderImpl._getVisibleType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#1      DartEditBuilderImpl._getVisibleType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#2      DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#3      DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#4      ListBase.every (dart:collection/list.dart)
#5      DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#6      DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#7      ListBase.every (dart:collection/list.dart)
#8      DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#9      DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#10     ListBase.every (dart:collection/list.dart)
#11     DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#12     DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#13     ListBase.every (dart:collection/list.dart)
#14     DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#15     DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#16     ListBase.every (dart:collection/list.dart)
#17     DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#18     DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#19     ListBase.every (dart:collection/list.dart)
#20     DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#21     DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#22     ListBase.every (dart:collection/list.dart)
#23     DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#24     DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#25     ListBase.every (dart:collection/list.dart)
#26     DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#27     DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#28     ListBase.every (dart:collection/list.dart)
#29     DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#30     DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#31     ListBase.every (dart:collection/list.dart)
#32     DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#33     DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#34     ListBase.every (dart:collection/list.dart)
#35     DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#36     DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#37     ListBase.every (dart:collection/list.dart)
#38     DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#39     DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#40     ListBase.every (dart:collection/list.dart)
#41     DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#42     DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#43     ListBase.every (dart:collection/list.dart)
...
...
#19255  ListBase.every (dart:collection/list.dart)
#19256  DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#19257  DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#19258  ListBase.every (dart:collection/list.dart)
#19259  DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#19260  DartEditBuilderImpl._canWriteType.<anonymous closure> (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#19261  ListBase.every (dart:collection/list.dart)
#19262  DartEditBuilderImpl._canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#19263  DartEditBuilderImpl.canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#19264  DartFileEditBuilderImpl.canWriteType (package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart)
#19265  AddTypeAnnotation._applyChange.<anonymous closure> (package:analysis_server/src/services/correction/dart/add_type_annotation.dart)
#19266  ChangeBuilderImpl.addDartFileEdit (package:analyzer_plugin/src/utilities/change_builder/change_builder_core.dart)
#19267  _SuspendState._createAsyncStarCallback.<anonymous closure> (dart:async-patch/async_patch.dart)
#19268  _rootRunUnary (dart:async/zone.dart)
#19269  Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart)
#19270  Future._propagateToListeners (dart:async/future_impl.dart)
#19271  Future._completeWithValue (dart:async/future_impl.dart)
#19272  _SuspendState._createAsyncStarCallback.<anonymous closure> (dart:async-patch/async_patch.dart)
#19273  _rootRunUnary (dart:async/zone.dart)
#19274  Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart)
#19275  Future._propagateToListeners (dart:async/future_impl.dart)
#19276  Future._completeWithValue (dart:async/future_impl.dart)
#19277  _SuspendState._createAsyncStarCallback.<anonymous closure> (dart:async-patch/async_patch.dart)
#19278  _rootRunUnary (dart:async/zone.dart)
#19279  _rootRun (dart:async/zone.dart)
#19280  _CustomZone.run (dart:async/zone.dart)
#19281  _CustomZone.runGuarded (dart:async/zone.dart)
#19282  _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart)
#19283  _microtaskLoop (dart:async/schedule_microtask.dart)
#19284  _startMicrotaskLoop (dart:async/schedule_microtask.dart)
#19285  _Timer._runTimers (dart:isolate-patch/timer_impl.dart)
#19286  _Timer._handleMessage (dart:isolate-patch/timer_impl.dart)
#19287  _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart)


#0      BulkFixProcessor._fixSingleDiagnostic (package:analysis_server/src/services/correction/bulk_fix_processor.dart:786)
<asynchronous suspension>
#1      BulkFixProcessor._fixErrorsInLibraryUnit (package:analysis_server/src/services/correction/bulk_fix_processor.dart:628)
<asynchronous suspension>
#2      BulkFixProcessor._fixErrorsInLibraryAt (package:analysis_server/src/services/correction/bulk_fix_processor.dart:577)
<asynchronous suspension>
#3      BulkFixProcessor._computeFixes (package:analysis_server/src/services/correction/bulk_fix_processor.dart:510)
<asynchronous suspension>
#4      EditBulkFixes.handle (package:analysis_server/src/handler/legacy/edit_bulk_fixes.dart:58)
<asynchronous suspension>
#5      LegacyAnalysisServer.handleRequest.<anonymous closure>.<anonymous closure> (package:analysis_server/src/legacy_analysis_server.dart:646)
<asynchronous suspension>
#6      OperationPerformanceImpl.runAsync (package:analyzer/src/util/performance/operation_performance.dart:199)
<asynchronous suspension>
#7      LegacyAnalysisServer.handleRequest.<anonymous closure> (package:analysis_server/src/legacy_analysis_server.dart:626)
<asynchronous suspension>


#0      BulkFixProcessor._fixSingleDiagnostic (package:analysis_server/src/services/correction/bulk_fix_processor.dart:786)
<asynchronous suspension>
#1      BulkFixProcessor._fixErrorsInLibraryUnit (package:analysis_server/src/services/correction/bulk_fix_processor.dart:628)
<asynchronous suspension>
#2      BulkFixProcessor._fixErrorsInLibraryAt (package:analysis_server/src/services/correction/bulk_fix_processor.dart:577)
<asynchronous suspension>
#3      BulkFixProcessor._computeFixes (package:analysis_server/src/services/correction/bulk_fix_processor.dart:510)
<asynchronous suspension>
#4      EditBulkFixes.handle (package:analysis_server/src/handler/legacy/edit_bulk_fixes.dart:58)
<asynchronous suspension>
#5      LegacyAnalysisServer.handleRequest.<anonymous closure>.<anonymous closure> (package:analysis_server/src/legacy_analysis_server.dart:646)
<asynchronous suspension>
#6      OperationPerformanceImpl.runAsync (package:analyzer/src/util/performance/operation_performance.dart:199)
<asynchronous suspension>
#7      LegacyAnalysisServer.handleRequest.<anonymous closure> (package:analysis_server/src/legacy_analysis_server.dart:626)
<asynchronous suspension>

When trying to apply a quick fix in Intellij where the warning is related to specify_nonobvious_local_variable_types, it doesn't do anything.

When checking where this happens, it always happens where a generic type is being used. I can not share file's content but I can share some obscured snippets if needed.

In all cases, here are some samples:
Example 1:

                final List<void Function(T model)> _onAdded = [];
                for (var element in _onAdded) {
                  final T model = event.modelsNow.firstWhere((T element) => element.id == change.doc.id);
                  element(model);
                }

the fix is

                final List<void Function(T model)> _onAdded = [];
                for (void Function(T model) element in _onAdded) {
                  final T model = event.modelsNow.firstWhere((T element) => element.id == change.doc.id);
                  element(model);
                }

Example 2:

  void addAll(Iterable<DocumentReference<T>> elements) {
    final newElements = elements.where((e) => state.allElements.contains(e) == false).toList();
    if (newElements.isEmpty) return;

    final updatedBatches = _addToBatches(state.batches, newElements);
    state = state.copyWith(batches: updatedBatches, allElements: {...state.allElements, ...newElements});
  }

the fix is

  void addAll(Iterable<DocumentReference<T>> elements) {
    final List<DocumentReference<T>> newElements = elements
        .where((e) => state.allElements.contains(e) == false)
        .toList();
    if (newElements.isEmpty) return;

    final List<WhereInBatch<DocumentReference<T>>> updatedBatches = _addToBatches(state.batches, newElements);
    state = state.copyWith(batches: updatedBatches, allElements: {...state.allElements, ...newElements});
  }

dart --version
Dart SDK version: 3.10.0 (stable) (Thu Nov 6 05:24:55 2025 -0800) on "macos_arm64"

*Edit: Moved final List<void Function(T model)> _onAdded = []; from example 2 to example 1 as it was a mistake.

[eernstg]

I implemented the lint specify_nonobvious_local_variable_types. However, this looks like it could be associated with the fix 'add type annotation' rather than the lint, or it could be associated with DartEditBuilderImpl._canWriteType which is entering the infinite loop in the first place (but that could of course be caused by ill-formed object graphs created somewhere else). Does it happen if you perform the refactoring 'add type annotation' directly?

@srawlins, WDYT?

[FMorschel]

I made the _canWriteType call itself recently. I'll help identify the problem and fix this.

Can you say where T is declared, @bh-oussama? Is it on a class/extension or directly on a method?

I've tested with:

void f<T>(List<void Function(T model)> list) {
  for (var element in list) {}
}

class C<T> {
  void m(List<void Function(T model)> list) {
    for (var element in list) {}
  }
}

And both work as expected in 3.10.0 and the latest master. I think there may be something here about where this type parameter is defined. It is trying to "Get a visible type" here, and it can't find anything. It should be smart enough to fall back to Object(?), but we may have missed this case.

One thing to note here is that from the reproduction I had above, I could not trigger specify_nonobvious_local_variable_types, only always_specify_types. Any ideas on how I can change my code to make the specified lint trigger instead, @eernstg?

Edit: The Add type annotation quick-fix does work without problem too. I suspect that it would fail (not show on the list) when we find the correct reproduction.

[bh-oussama]

@FMorschel
T is defined on class level but there's more. So the class is defined as follows class WhereInBatchingNotifier<T extends ModelBase<T>> extends _$WhereInBatchingNotifier<T> while ModelBase is defined as abstract class ModelBase<T extends ModelBase<T>>.

For me, I've set analysis_options.yaml to have specify_nonobvious_local_variable_types and not always_specify_types.

I don't think there is a value in sharing analysis_options.yaml but anyways, here it is:

include: package:flutter_lints/flutter.yaml

analyzer:
  exclude:
    - lib/generated/**
    - lib/**/*.g.dart

linter:
  rules:
    - avoid_print
    - prefer_single_quotes
    - prefer_const_declarations
    - prefer_const_constructors_in_immutables
    - prefer_const_constructors
    - prefer_relative_imports
    - specify_nonobvious_local_variable_types
    - specify_nonobvious_property_types

[eernstg]

The provided source code does not reveal many things. In particular, we can't see how _onAdded is declared in this snippet:

                for (var element in _onAdded) {
                  final T model = event.modelsNow.firstWhere((T element) => element.id == change.doc.id);
                  element(model);
                }

However, if _onAdded has a non-obvious type (e.g., if it is a non-local variable such as an instance variable) then the type of element will be requested by specify_nonobvious_local_variable_types.

[FMorschel]

For me, I've set analysis_options.yaml to have specify_nonobvious_local_variable_types and not always_specify_types.

I noticed. I only added always_specify_types to my testing to be sure this wasn't a problem specifically with the CLI for dart fix, since I could not reproduce the specify_nonobvious_local_variable_types diagnostic there yet.

I don't think there is a value in sharing analysis_options.yaml but anyways

It should not make a difference, but it doesn't hurt to share. Thanks!

T is defined on class level but there's more. So the class is defined as follows class WhereInBatchingNotifier<T extends ModelBase<T>> extends _$WhereInBatchingNotifier<T> while ModelBase is defined as abstract class ModelBase<T extends ModelBase<T>>.

Thank you for the information!

[I]f it is a non-local variable such as an instance variable

I'll give it a try, thanks!

[bh-oussama]

@eernstg Sorry for the confusion. By mistake, I've put _onAdded declaration under Example 2 instead of Example 1. I've edited the issue description.

[FMorschel]

This reproduces the problem. And as I suspected, there is no Add type annotation on the quick-fix list (since it fails internally too, it doesn't show up).

class Foo<T extends Foo<T>> {
  List<T> list = [];
  void m() {
    for (var element in list) {}
  }
}

I'll work on a fix. Thanks for filing this issue @bh-oussama!

[eernstg]

I've put _onAdded declaration under Example 2 instead of Example 1. I've edited the issue description.

OK! But in that case _onAdded is a local variable with a type annotation, which implies that it has an obvious type according to the lint (the reasoning is: "you can find the declaration of this variable a few lines away, and the declaration ought to document the type sufficiently for your own taste"). In that case the lint shouldn't flag the iteration variable.

In any case, I don't think this has much to do with the lint, it seems more likely that it is a situation that causes AddTypeAnnotation to loop.

[bh-oussama]

But in that case _onAdded is a local variable with a type annotation
_onAdded is a private member of the class.

This should be clear enough now:

abstract class Foo<T extends Foo<T>>{}

class ClassA<T extends Foo<T>> extends _$ClassA<T> {
  final List<void Function(T model)> _onAdded = [];

  foo(){
    // Some logic

    final event = ...;

    for (var element in _onAdded) {
      final T model = event.modelsNow.firstWhere((T element) => element.id == change.doc.id);
      element(model);
    }

    // Some logic
  }

}

Sorry for the confusion again. This is the first time I am filing an issue for a non-internal repo.

[eernstg]

OK, thanks! Now _onAdded is an instance variable, and their types are not considered obvious, even in the case where they have a type annotation, and are not many lines of code away from the use site.

[FMorschel]

Just on a temporary note. I found two problems:

1. The error in question (the stack overflow)
2. It getting to this point. It should be possible for it to detect that the type parameter definition is in the enclosing class, but for some reason, it doesn't detect the enclosing class, and that causes it to try and write the bound (so we get the first error).

I'll see if I can fix both, but the second one may be harder.

[FMorschel]

Here is the CL for the first problem:

https://dart-review.googlesource.com/c/sdk/+/469201

I'll try reproducing the second error in a test now.

[FMorschel]

Okay, I found out why my tests were not triggering the second problem.

The second problem happened because we had a canWriteType function that created an edit builder at offset 0 in the file. That led to our test suite always passing since we basically never have import statements or anything before the class declaration, really.

So when it is called, the canWriteType got the first class as the class scope for our tests, but no scope for most of the real-world code. I've fixed that as a patch for the same CL.