[breaking change] Null safety changes

[mit-mit]

This is a meta-issue summarizing breaking changes made as part of realizing the null safety feature.

We are planning on landing these breaking changes fairly soon, and this in advance of the full null safety feature to ensure that we have sufficient time to uncover any unanticipated consequences.

Language

• type system
  • Breaking Change Request: normalize types and use mutual subtyping for type parameter bounds #40633: Types objects will now be normalized
  • Breaking Change Request: normalize types and use mutual subtyping for type parameter bounds #40633: Subtyping of type bounds in function types will switch from using structural subtyping to use mutual subtyping.
  • Breaking Change Request: Don't infer promoted types on local variables #40675: Type inference for local variables will not use promoted type variables.

Core libraries

• dart:core

  • [Breaking change request] RuneIterator.current and .rawIndex no longer returns null. #40674: The RuneIterator class has some members which return null in the state where the iterator has no "current" element; they will now return -1 or an empty string
  • [Breaking change request] String.fromEnvironment and int.fromEnvironment const constructors will have a non-null defaultValue default value. #40678: The String.fromEnvironment and int.fromEnvironment const constructors will have a non-null defaultValue default value.
  • [Breaking change request] Make TypeError not extend AssertionError #40317: We will make the platform TypeError class not extend/implement the AssertionError class.
    That will also make it not inherit the message getter.

• dart:async:

  • [Breaking change request] The runZoned method will now not catch synchronously thrown errors even when given an error handler. #40681: The runZoned method will now not catch synchronously thrown errors even when given an error handler.
  • [Breaking change request] StreamSubscription.cancel can no longer return null #40676: The StreamSubscription.cancel method's return type is changed to Future<void>.
  • [Breaking change request] Errors cannot be null. #40683: We disallow throwing nullable values entirely, and methods which accept thrown objects requires non-null arguments. This includes methods accepting async errors.
  • [Breaking change request] Make stack traces not be null. #40130: We will replace a null stack trace supplied by users with a default stack trace.

• dart:io:

  • [Breaking Change Request] Throw StateError in meaningless getters on detached processes #40483: Detached processes now throws StateError on meaningless getters
  • [Breaking Change Request] Destroyed/Upgraded Sockets now throw when accessing socket options #40702: Destroyed/Upgraded Sockets now throw when accessing socket options
  • [Breaking Change Request] Provide epoch timestamps in the FileStat notFound object #40706: Provide epoch timestamps in the FileStat notFound object
  • [Breaking Change Request] Fix HeaderValue parsing, toString(), and support null values #40709: HeaderValue parses invalid parameters as empty string instead of null

[franklinyow]

Announced : https://groups.google.com/a/dartlang.org/g/announce/c/JwPWiC0jTiU

[ghost]

Announced : https://groups.google.com/a/dartlang.org/g/announce/c/JwPWiC0jTiU

This link is broken (404).

[franklinyow]

Ok, let's try this:

https://groups.google.com/a/dartlang.org/d/msg/announce/JwPWiC0jTiU/diljrydDCQAJ

[franklinyow]

All issues landed

[mit-mit]

@franklinyow looks like some of these might be missing from https://github.com/dart-lang/sdk/blob/master/CHANGELOG.md?