The following Dart core library APIs, which are all currently deprecated, are now being fully removed.

This is the continuation of previous discontinuation work tracked in #34233

Phase II, scheduled for Dart 3.0

The following APIs are planned to be removed in 3.0, as some breakage is to be expected.

API changes which we believe are minimally breaking

dart:core

• onError argument to int.parse, double.parse, num.parse:
  CL: https://dart-review.googlesource.com/c/sdk/+/259042
• proxy constant:
  CL: https://dart-review.googlesource.com/c/sdk/+/258004
• Provisional class and associated constant:
  CL: https://dart-review.googlesource.com/c/sdk/+/258004
• List constructor (use List.Filled):
  CL: https://dart-review.googlesource.com/c/sdk/+/258920
• BidirectionalIterator class:
  CL: https://dart-review.googlesource.com/c/sdk/+/276741
• Deprecated.expires getter on Deprecated. Use Deprecated.message instead.
• Errors:
  • AbstractClassInstantiationError class (no longer relevant in dart:core libraries. dart:mirrors may still throw it and now has it's own definition of it):
    CL: https://dart-review.googlesource.com/c/sdk/+/274383
  • CastError class (use TypeError):
    https://dart-review.googlesource.com/c/sdk/+/259041
  • FallThroughError class (Unused since Dart 2.0):
    https://dart-review.googlesource.com/c/sdk/+/261860,
    CL: https://dart-review.googlesource.com/c/sdk/+/259041
  • NoSuchMethodError default constructor (use the named constructor NoSuchMethod.withInvocation):
    CL: https://dart-review.googlesource.com/c/sdk/+/271082
  • CyclicInitializationError (will never be thrown from code with sound null safety):
    https://dart-review.git.corp.google.com/c/sdk/+/275120
  • NullThrownError (will never be thrown from code with sound null safety):
    https://dart-review.googlesource.com/c/sdk/+/275840

dart:async

• DeferredLibrary class (use the deferred as import syntax):
  CL: https://dart-review.git.corp.google.com/c/sdk/+/268460

dart:developer

• MAX_USER_TAGS in UserTag:
  CL: https://dart-review.git.corp.google.com/c/sdk/+/268340

dart:mirrors

None.

dart:html

• document.registerElement & registerElement2:
  [dart:html] Breaking change: delete registerElement* APIs in dart:html #49536,
  CL 📝: https://dart-review.git.corp.google.com/c/sdk/+/268461
  

API changes which may be more breaking

These are postponed, and not planned for inclusion in Dart 3.

### dart:core

• [ ] IntegerDivisionByZeroException exception (use UnsupportedError ):
  Remove IntegerDivisionByZeroException #30743
• [ ] Errors:

### dart:async

• [ ] runZoned arg on onError:
  CL: https://dart-review.googlesource.com/c/sdk/+/248002