The compiler crashed: NoSuchMethodError: The getter 'boxedVariables' was called on null.

[long1eu]

Target dart2js failed: Exception: .dart_tool/flutter_build/1d8a7e17755c385f5f018965fb9ccbf2/app.dill:
Internal Error: The compiler crashed when compiling this element.
The compiler is broken.

When compiling the above element, the compiler crashed. It is not
possible to tell if this is caused by a problem in your program or
not. Regardless, the compiler should not crash.

The Dart team would greatly appreciate if you would take a moment to
report this problem at http://dartbug.com/new.

Please include the following information:

• the name and version of your operating system,

• the Dart SDK build number (2.16.1), and

• the entire message you see here (including the full stack trace
  below as well as the source location above).

The compiler crashed: NoSuchMethodError: The getter 'boxedVariables' was called on null.
Receiver: null
Tried calling: boxedVariables
#0      JsKernelToElementMap.makeRecordContainer (package:compiler/src/js_model/element_map_impl.dart:1769:14)
#1      ClosureDataBuilder.createClosureEntities.<anonymous closure> (package:compiler/src/js_model/closure.dart:328:23)
#2      _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:539:8)
#3      ClosureDataBuilder.createClosureEntities (package:compiler/src/js_model/closure.dart:326:19)
#4      JsClosedWorldBuilder.convertClosedWorld (package:compiler/src/js_model/js_world_builder.dart:161:41)
#5      JsBackendStrategy.createJClosedWorld (package:compiler/src/js_model/js_strategy.dart:175:52)
#6      Compiler.closeResolution (package:compiler/src/compiler.dart:594:25)
#7      Compiler.computeClosedWorld (package:compiler/src/compiler.dart:464:9)
#8      Compiler.compileFromKernel.<anonymous closure>.<anonymous closure> (package:compiler/src/compiler.dart:561:17)
#9      CompilerTask.measureSubtask (package:compiler/src/common/tasks.dart:181:35)
#10     Compiler.compileFromKernel.<anonymous closure> (package:compiler/src/compiler.dart:560:44)
#11     CompilerTask.measureSubtask (package:compiler/src/common/tasks.dart:181:35)
#12     Compiler.compileFromKernel (package:compiler/src/compiler.dart:559:14)
#13     Compiler.runInternal (package:compiler/src/compiler.dart:363:17)
<asynchronous suspension>
#14     main (package:compiler/src/dart2js.dart:1373:3)
<asynchronous suspension>

[sigmundch]

Thanks for the bug report! I believe this is a duplicate of #47916, especially if your project is using package:freezed. That issue has been fixed in our main branch, but hasn't yet been released. There is an ongoing hotfix to get this out in the current beta and stable channels.