Analyzer doesn't prompt quick fix to import for extension in null-aware access

[ChaserVasya]

extension.dart

extension MapT<T extends Object> on T {
  Output map<Output>(Output Function(T) mapper) => mapper(this);
}

main.dart

void main(){
    String? str = null;
    str?.map(print);
}

Analyzer doesn't find quick-fix for extension importing:

But quick-fix is exists: import adding.
main.dart

import 'extension.dart';

void main() {
  String? str = null;
  str?.map(print);
}

#Desired behavior:
Quick-fix shows import extension.dart

fvm dart info

General info

• Dart 3.2.3 (stable) (Tue Dec 5 17:58:33 2023 +0000) on "macos_arm64"
• on macos / Version 14.5 (Build 23F79)
• locale is ru-RU

Process info

Memory	CPU	Elapsed time	Command line
3 MB	0.0%	32-00:43:27	dart devtools --no-launch-browser
11 MB	0.0%	01-21:24:48	dart devtools --no-launch-browser
3 MB	0.0%	37-00:34:47	dart devtools --no-launch-browser
3 MB	0.0%	52-23:03:27	dart devtools --no-launch-browser
4 MB	0.0%	33-11:34:33	dart devtools --no-launch-browser
3 MB	0.0%	53-21:23:57	dart devtools --no-launch-browser
1656 MB	0.0%	01:55:10	dart language-server --client-id=Android-Studio --client-version=AI-233.14808.21 --protocol=analyzer
137 MB	0.0%	01:55:12	flutter_tools.snapshot daemon
90 MB	59.8%	00:01	main.dart-3.4.0.snapshot dart info

[dart-github-bot]

Summary: The Dart analyzer fails to suggest importing an extension file when a user attempts to use an extension method defined in that file. The expected behavior is for the analyzer to provide a quick-fix that adds the necessary import statement.

[srawlins]

This appears to be related directly to the null-aware component. See this example:

void f(String str1, String? str2){
    str1.map(print);
    str2?.map(print);
}

On both lines I get an error that map is unknown. For the second line, I do not get suggestions to import the library containing map. But for the first line, I do.

[FMorschel]

This is because when inside NotInstantiatedExtensionsExtensions<R>.applicableTo it tests isSubtypeOf testing if String? is a subtype of String which it is not. It doesn't consider the possibility of using ?.. I'll take a look and see if I can fix it later.

https://github.com/dart-lang/sdk/blob/main/pkg/analyzer/lib/src/dart/resolver/applicable_extensions.dart#L245

[srawlins]

I have a fix that instead changes SimpleIdentifier.targetType in import_library.dart.