chore: update dependency dart to v3.8.0

[renovate]

This PR contains the following updates:

Package	Update	Change
dart (source)	minor	3.4.4 -> 3.8.0

---

Release Notes

dart-lang/sdk (dart)

v3.8.0

Compare Source

Released on: 2025-05-20

Language

Dart 3.8 adds null-aware elements to the language. To use them, set
your package's [SDK constraint][language version] lower bound to 3.8
or greater (sdk: '^3.8.0').

Null-Aware Elements

Null-aware elements make it easier to omit a value from a collection literal if
it's null. The syntax works in list literals, set literals, and map literals.
For map literals, both null-aware keys and values are supported. Here is an
example a list literal written in both styles, without the null-aware elements
language feature and with it:

String? lunch = isTuesday ? 'tacos!' : null;

var withoutNullAwareElements = [
  if (lunch != null) lunch,
  if (lunch.length != null) lunch.length!,
  if (lunch.length case var length?) length,
];

var withNullAwareElements = [
  ?lunch,
  ?lunch.length,
  ?lunch.length,
];

Full details are in the feature specification.

Libraries

dart:core

• Added Iterable.withIterator constructor.

dart:io

• Added HttpClientBearerCredentials.
• Updated Stdout.supportsAnsiEscapes and Stdin.supportsAnsiEscapes to
  return true for TERM containing tmux values.

dart:html

• Breaking change: Native classes in dart:html, like HtmlElement, can no
  longer be extended. Long ago, to support custom elements, element classes
  exposed a .created constructor that adhered to the v0.5 spec of web
  components. On this release, those constructors have been removed and with
  that change, the classes can no longer be extended. In a future change, they
  may be marked as interface classes as well. This is a follow up from an
  earlier breaking change in 3.0.0 that removed the registerElement APIs. See
  #​53264 for details.

dart:ffi

• Added Array.elements which exposes an Iterable over the Array's content.

Tools

Analyzer

• The analyzer now supports "doc imports," a new comment-based syntax which
  enables external elements to be referenced in documentation comments without
  actually importing them. See the
  documentation
  for details.
• Code completion is improved to offer more valid suggestions. In particular,
  the suggestions are improved when completing text in a comment reference on a
  documentation comment for an extension, a typedef, or a directive (an import,
  an export, or a library). Additionally, instance members can now be suggested
  in a documentation comment reference.
• Offer additional assist to wrap a Flutter widget with a FutureBuilder widget.
• Add a quick assist to wrap with ValueListenableBuilder.
• Add a quick fix to convert an (illegal) extension field declaration into a
  getter declaration.
• Add a quick fix to help code comply with a few lint rules that encourage
  omitting types: omit_local_variable_types,
  omit_obvious_local_variable_types, and omit_obvious_property_types.
• Add a quick fix to create an extension method to resolve an "undefined method
  invocation" error.
• Renaming a closure parameter is now possible.
• Renaming a field now adjusts implicit this references in order to avoid
  name collisions.
• Renaming a field formal parameter now properly renames known super-parameters
  in subclasses in other libraries.
• Renaming a method parameter now properly renames across the type hierarchy.
• The "encapsulate field" quick assist now works on final fields.
• The "inline method" refactoring now properly handles inner closures.
• The quick fix that adds names to a show clause or removes names from a
  hide clause can now add or remove multiple names simultaneously, in order to
  resolve as many "undefined" errors as possible.
• The "remove const" quick fix now operates on more types of code.
• The "add missing required argument" quick fix can now add multiple missing
  required arguments.
• Add a new warning that reports an import or export directive with multiple
  show or hide clauses, which are never necessary.
• Add a quick fix for this warning.
• Add LSP document links for lint rules in analysis options files.
• Add LSP document links for dependency packages in pubspec files.
• Fix various issues around patterns, like highlighting, navigation, and
  autocompletion.
• Add the [use_null_aware_elements][use_null_aware_elements] lint rule.
• Add the experimental [unnecessary_ignore][unnecessary_ignore] lint rule.
• (Thanks @​FMorschel for many of the above
  enhancements!)

Dart Development Compiler (dartdevc)

In order to align with dart2js semantics, DDC will now throw a runtime error
when a redirecting factory is torn off and one of its optional non-nullable
parameters is provided no value. The implicit null passed to the factory will
not match the non-nullable type and this will now throw.

In the future this will likely be a compile-time error and will be entirely
disallowed.

Dart to Javascript Compiler (dart2js)

Removed the --experiment-new-rti and --use-old-rti flags.

Dart Native Compiler

Added cross-compilation for the Linux x64 and Linux ARM64 target platforms.

Dart format

In 3.7.0, we released a largely rewritten formatter supporting a new
"tall" style. Since then, we've gotten a lot of feedback and bug
reports and made a number of fixes in response to that.

Features

Some users strongly prefer the old behavior where a trailing comma will be
preserved by the formatter and force the surrounding construct to split. That
behavior is supported again (but off by default) and can enabled by adding this
to a surrounding analysis_options.yaml file:

formatter:
  trailing_commas: preserve

This is similar to how trailing commas work in the old short style formatter
applied to code before language version 3.7.

Bug fixes

• Don't add a trailing comma in lists that don't allow it, even when there is
  a trailing comment (#​1639).

Style changes

The following style changes are language versioned and only affect code whose
language version is 3.8 or later. Dart code at 3.7 or earlier is formatted the
same as it was before.

• Allow more code on the same line as a named argument or =>.

  // Before:
  function(
    name:
        (param) => another(
          argument1,
          argument2,
        ),
  );
  
  // After:
  function(
    name: (param) => another(
      argument1,
      argument3,
    ),
  );

• Allow the target or property chain part of a split method chain on the RHS of
  =, :, and =>.

  // Before:
  variable =
      target.property
          .method()
          .another();
  
  // After:
  variable = target.property
      .method()
      .another();

• Allow the condition part of a split conditional expression on the RHS of =,
  :, and =>.

  // Before:
  variable =
      condition
      ? longThenBranch
      : longElseBranch;
  
  // After:
  variable = condition
      ? longThenBranch
      : longElseBranch;

• Don't indent conditional branches redundantly after =, :, and =>.

  // Before:
  function(
    argument:
        condition
            ? thenBranch
            : elseBranch,
  )
  
  // After:
  function(
    argument:
        condition
        ? thenBranch
        : elseBranch,
  )

• Indent conditional branches past the operators.

  // Before:
  condition
      ? thenBranch +
          anotherOperand
      : elseBranch(
        argument,
      );
  
  // After:
  condition
      ? thenBranch +
            anotherOperand
      : elseBranch(
          argument,
        );

• Block format record types in typedefs:

  // Before:
  typedef ExampleRecordTypedef =
      (
        String firstParameter,
        int secondParameter,
        String thirdParameter,
        String fourthParameter,
      );
  
  // After:
  typedef ExampleRecordTypedef = (
    String firstParameter,
    int secondParameter,
    String thirdParameter,
    String fourthParameter,
  );

• Eagerly split argument lists whose contents are complex enough to be easier
  to read spread across multiple lines even if they would otherwise fit on a
  single line.

  The heuristic is that the argument list must contain at least three named
  arguments, some of which are nested and some of which are not.

  // Before:
  TabBar(tabs: [Tab(text: 'A'), Tab(text: 'B')], labelColor: Colors.white70);
  
  // After:
  TabBar(
    tabs: [
      Tab(text: 'A'),
      Tab(text: 'B'),
    ],
    labelColor: Colors.white70,
  );

v3.7.3

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Released on: 2025-04-16

This is a patch release that:

• Fixes a performance regression in the analysis server (issue #​60335).

v3.7.2

Compare Source

Released on: 2025-03-12

This is a patch release that:

• Fixes a bug in dart2wasm that imports a js-string builtin function with a
  non-nullable parameter type where it must use a nullable one (issue #​59899).

v3.7.1

Compare Source

Released on: 2025-02-26

This is a patch release that:

• Fixes a bug in the DevTools network profiler that was causing network
  traffic to be dropped (issue #​8888).
• Fixes a bug in DDC that prevents code from compiling when it includes
  factory constructors containing generic local functions (issue #​160338).
• Fixes a bug in the CFE that didn't correctly mark wildcard variables
  in formal parameters, causing the wildcard variables to appear in
  variable lists while debugging (issue #​60121).

v3.7.0

Compare Source

Released on: 2025-02-12

Language

Dart 3.7 adds wildcard variables and inference using
bounds to the language. To use
them, set your package's [SDK constraint][language version] lower
bound to 3.7 or greater (sdk: '^3.7.0').

Wildcard Variables

Local variables and parameters named _ are now non-binding and they can
be declared multiple times without collisions. You will no longer be able to use
these variables nor access their values. All wildcard variable declaration types
that have this behavior are described in the
wildcard variables specification.

Top-level variables, top-level function names, type names, member names, etc.
are unchanged. They can be named _ and used as they are today.

These are a few examples of where wildcard variables can be used:

Foo(_, this._, super._, void _()) {}

main() {
  var _ = 1;
  int _ = 2;

  list.where((_) => true);
}

Inference Using Bounds

With the inference using bounds feature, Dart's type inference
algorithm generates constraints by combining existing constraints with
the declared type bounds, not just best-effort approximations.

This is especially important for F-bounded types, where inference
using bounds correctly infers that, in the example below, X can be
bound to B. Without the feature, the type argument must be specified
explicitly: f<B>(C()):

class A<X extends A<X>> {}

class B extends A<B> {}

class C extends B {}

void f<X extends A<X>>(X x) {}

void main() {
  f(B()); // OK.

  // OK with this feature. Without it, inference fails after detecting
  // that C is not a subtype of A<C>.
  f(C());

  f<B>(C()); // OK.
}

The feature is described in more details in the
inference using bounds specification.

Other Language Changes

• Breaking Change #​56893: If a field is promoted to the type Null
  using is or as, this type promotion is now properly accounted for in
  reachability analysis. This makes the type system more self-consistent,
  because it mirrors the behavior of promoted local variables. This change is
  not expected to make any difference in practice.

Tools

Analyzer

• Add a new 'Go to imports' command to find the import directives that export a
  declaration.
• Assists and quick fixes that add an import now consider the
  prefer_relative_imports and always_use_package_imports lint rules.
• Add a new fix that converts a ~/ operation into /, when the ~/
  operation is not available.
• Add a fix that wraps an expression in await if the expression is currently
  not assignable, but awaiting it would make it assignable.
• Assists and quick fixes that convert a forEach call into a for-loop now
  consider the prefer_final_in_for_each and always_specify_types lint
  rules.
• Add an additional fix to correct a cascade_invocations lint rule violation.
• Offer additional assists to wrap a Flutter widget with an Expanded widget,
  and with a Flexible widget.
• Offer an assist to "inline" an else-block's inner if-statement with the
  else-block to read else if.
• Add a fix to use_decorated_box by swapping the Container with
  ColoredBox as suggested by the lint.
• Add an additional fix to import an unknown prefixed identifier by updating
  the show combinator on an existing import.
• Add a fix to import an unknown prefixed identifier by adding an
  import directive with the given prefix.
• Add a fix to import an unknown prefixed identifier by removing a hide
  combinator.
• Add a fix to import an unknown identifier by adding an import directive with a
  show combinator, and optionally a prefix.
• Code completion now suggests instance variables when completing inside the
  initializer of a late field.
• Assists and quick fixes that add a const keyword now consider the
  prefer_const_declarations lint rule, preferring to add const to a variable
  declaration rather than the initial value.
• Add a fix to add a missing on keyword in an extension declaration.
• Add a fix to wrap an ambiguous property access or method call in an extension
  override.
  (Thanks @​FMorschel for the above enhancements!
• The 'sort members' command now considers the sort_constructors_first lint
  rule.
• The 'extract method' refactoring now uses generic method syntax for
  function-typed parameters.
• Add quick fixes for more than 30 diagnostics.
• Add the [strict_top_level_inference][strict_top_level_inference] lint rule.
• Add the [unnecessary_underscores][unnecessary_underscores] lint rule.
• Add the experimental [specify_nonobvious_property_types][specify_nonobvious_property_types] lint rule.
• Add the experimental [omit_obvious_property_types][omit_obvious_property_types] lint rule.
• Add the experimental [unnecessary_async][unnecessary_async] lint rule.
• Add the experimental [unsafe_variance][unsafe_variance] lint rule.
• Remove the [package_api_docs][package_api_docs] lint rule.
• Remove the [unsafe_html][unsafe_html] lint rule.

Dart format

The formatter implements a new style better suited for the kind of
declarative code that many Dart users are writing today. The new style looks
similar to the style you get when you add trailing commas to argument lists,
except that now the formatter will add and remove those commas for you.

The dart format command uses the language version of
each input file to determine which style it gets. If the language version is 3.6
or lower, the code is formatted with the old style. If 3.7 or later, it gets the
new tall style.

You typically control the language version by setting a min SDK constraint in
your package's pubspec. This means that when you update the SDK
constraint in your pubspec to move to 3.7, you are also opting in to the new
style.

In order to correctly determine the language version of each file it formats,
dart format (like other dart commands) looks for a package_config.json
file surrounding the files being formatted. This means that you need to run
dart pub get before formatting code in your package. If you have format
checks in your continuous integration server, you'll want to make sure it runs
dart pub get too.

We don't intend to support both styles indefinitely. At some point in the
future when most of the ecosystem is on 3.7 or later, support for the old style
will be removed.

In addition to the new formatting style, a number of other changes are included,
some of them breaking:

• Project-wide page width configuration. By long request, you can now
  configure your preferred formatting page width on a project-wide basis. When
  formatting a file, the formatter will look in the file's directory and any
  surrounding directories for an analysis_options.yaml file. If it finds one,
  it looks for YAML like so:

  formatter:
    page_width: 123

  If it finds a page width matching that schema, then the file is formatted
  using that width. Since the formatter will walk the surrounding directories
  until it finds an analysis_options.yaml file, this can be used to globally
  set the page width for an entire directory, package, or even collection of
  packages. Since analysis_options.yaml files already support an include
  key to reference other analysis_options.yaml files, you can define a single
  configuration and share it across a number of packages.

• Opting out a region of code from formatting. In code formatted using the
  new style, you can use a pair of special marker comments to opt a region of
  code out of automated formatting:

  main() {
    this.isFormatted();
    // dart format off
    no   +   formatting
      +
        here;
    // dart format on
    formatting.isBackOnHere();
  }

  The comments must be exactly // dart format off and // dart format on.
  A file may have multiple regions, but they can't overlap or nest.

  This can be useful for highly structured data where custom layout helps the
  reader understand the data, like large lists of numbers.

• Overriding the page width for a single file. In code formatted
  using the new tall style, you can use a special marker comment to control the
  page width that it's formatted using:

  // dart format width=30
  main() {
    someExpression +
        thatSplitsAt30;
  }

  This comment must appear before any code in the file and must match that
  format exactly. The width set by the comment overrides the width set by any
  surrounding analysis_options.yaml file.

  This feature is mainly for code generators that generate and immediately
  format code but don't know about any surrounding analysis_options.yaml
  that might be configuring the page width. By inserting this comment in the
  generated code before formatting, it ensures that the code generator's
  behavior matches the behavior of dart format.

  End users should mostly use analysis_options.yaml for configuring their
  preferred page width (or do nothing and continue to use the default page width
  of 80).

• Breaking change: Remove support for dart format --fix. Instead, use
  dart fix. It supports all of the fixes that dart format --fix could apply
  and many more.

• Treat the --stdin-name name as a path when inferring language version.
  When reading input on stdin, the formatter still needs to know its language
  version to know what style to apply. If the --stdin-name option is set, then
  that is treated as a file path and the formatter looks for a package config
  surrounding that file path to infer the language version from.

  If you don't want that behavior, pass in an explicit language version using
  --language-version=, or use --language-version=latest to parse the input
  using the latest language version supported by the formatter.

  If --stdin-name and --language-version are both omitted, then the
  formatter parses stdin using the latest supported language version.

• Rename the --line-length option to --page-width. This is consistent
  with the public API, internal implementation, and docs, which all use "page
  width" to refer to the limit that the formatter tries to fit code into.

  The --line-length name is still supported for backwards compatibility, but
  may be removed at some point in the future. You're encouraged to move to
  --page-width. Use of this option (however it's named) is rare, and will
  likely be even rarer now that project-wide configuration is supported, so
  this shouldn't affect many users.

Dart to Javascript Compiler (dart2js)

The dart2js compiler which is invoked when the command 'dart compile js' is
used has been switched to use an AOT snapshot instead of a JIT snapshot.

Dart Development Compiler (dartdevc)

The dartdevc compiler and kernel_worker utility have been switched to use an
AOT snapshot instead of a JIT snapshot, the SDK build still includes a JIT
snapshot of these tools as package build/build_web_compiler depends on it. The
AOT snapshot can be used as follows to run DDC /bin/dartaotruntime /bin/snapshots/dartdevc_aot.dart.snapshot

Libraries

dart:html

• dart:html is marked deprecated and will be removed in an upcoming release.
  Users should migrate to using dart:js_interop and package:web. See
  #​59716.

dart:indexed_db

• dart:indexed_db is marked deprecated and will be removed in an upcoming
  release. Users should migrate to using dart:js_interop and package:web.
  See #​59716.

dart:io

• HttpException will be thrown by HttpClient and HttpServer if a NUL
  (0x00) appears in a received HTTP header value.

dart:svg

• dart:svg is marked deprecated and will be removed in an upcoming release.
  Users should migrate to using dart:js_interop and package:web. See
  #​59716.

dart:web_audio

• dart:web_audio is marked deprecated and will be removed in an upcoming
  release. Users should migrate to using dart:js_interop and package:web.
  See #​59716.

dart:web_gl

• dart:web_gl is marked deprecated and will be removed in an upcoming release.
  Users should migrate to using dart:js_interop and package:web. See
  #​59716.

dart:js

• dart:js is marked deprecated and will be removed in an upcoming release.
  Users should migrate to using dart:js_interop. See #​59716.

dart:js_util

• dart:js_util is marked deprecated and will be removed in an upcoming
  release. Users should migrate to using dart:js_interop. See #​59716.

v3.6.2

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Released on: 2025-01-30

• Fixes a bug where HttpServer responses were not correctly encoded
  if a "Content-Type" header was set (issue #​59719).
• Fix dart format to parse code at language version 3.6 so that digit
  separators can be parsed correctly (issue #​59815, dart_style issue
  #​1630).
• Fixes an issue where the DevTools analytics did not distinguish
  between new and legacy inspector events (issue #​59884).
• When running dart fix on a folder that contains a library with multiple
  files and more than one needs a fix, the fix will now be applied correctly
  only once to each file (issue #​59572).

v3.6.1

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Released on: 2025-01-08

• When inside a pub workspace, pub get will now delete stray
  .dart_tool/package_config.json files in directories between the
  workspace root and workspace directories. Preventing confusing behavior
  when migrating a repository to pub workspaces (issue pub#4445).
• Fixes crash during AOT and dart2wasm compilation which was caused by
  the incorrect generic covariant field in a constant object (issue
  #​57084).
• Fixes analysis options discovery in the presence of workspaces
  (issue #​56552).

v3.6.0

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Released on: 2024-12-11

Language

Dart 3.6 adds digit separators to the language. To use them, set your
package's [SDK constraint][language version] lower bound to 3.6 or greater
(sdk: '^3.6.0').

Digit separators

Digits in number literals (decimal integer literals, double literals,
scientific notation literals, and hexadecimal literals) can now include
underscores between digits, as "digit separators." The separators do not change
the value of a literal, but can serve to make the number more readable.

100__000_000__000_000__000_000  // one hundred million million millions!
0x4000_0000_0000_0000
0.000_000_000_01
0x00_14_22_01_23_45  // MAC address

Separators are not allowed at the start of a number (this would be parsed as an
identifier), at the end of a number, or adjacent to another character in a
number, like ., x, or the e in scientific notation.

• Breaking Change #​56065: The context used by the compiler and analyzer
  to perform type inference on the operand of a throw expression has been
  changed from the "unknown type" to Object. This makes the type system more
  self-consistent, because it reflects the fact that it's not legal to throw
  null. This change is not expected to make any difference in practice.

Libraries

dart:io

• Breaking Change #​52444: Removed the Platform() constructor, which
  has been deprecated since Dart 3.1.

• Breaking Change #​53618: HttpClient now responds to a redirect
  that is missing a "Location" header by throwing RedirectException, instead
  of StateError.

dart:js_interop

• Added constructors for JSArrayBuffer, JSDataView, and concrete typed array
  types e.g. JSInt8Array.
• Added length and []/[]= operators to JSArray.
• Added toJSCaptureThis so this is passed in from JavaScript to the
  callback as the first parameter.
• Added a static from method on JSArray to create a JSArray from a given
  JavaScript iterable or array-like object.

Tools

CFE

• Breaking Change #​56466: The implementation of the UP and
  DOWN algorithms in the CFE are changed to match the specification
  and the corresponding implementations in the Analyzer. The upper and
  lower closures of type schemas are now computed just before they are
  passed into the subtype testing procedure instead of at the very
  beginning of the UP and DOWN algorithms.

Dart format

• Preserve type parameters on old-style function-typed formals that also use
  this. or super..
• Correctly format imports with both as and if clauses.

Wasm compiler (dart2wasm)

• The condition dart.library.js is now false on conditional imports in
  dart2wasm. Note that it was already a static error to import dart:js
  directly (see #​55266).

Pub

• Support for workspaces. This allows you to develop and resolve multiple
  packages from the same repo together. See https://dart.dev/go/pub-workspaces
  for more info.

• New command dart pub bump. Increments the version number of the current
  package.

  For example: dart pub bump minor will change the version from 1.2.3 to
  1.3.0.

• New validation: dart pub publish will warn if your git status is not
  clean.

• New flag dart pub upgrade --unlock-transitive.

• dart pub upgrade --unlock-transitive pkg, will unlock and upgrade all the
  dependencies of pkg instead of just pkg.

Analyzer

• Add the [use_truncating_division][use_truncating_division] lint rule.
• Add the experimental [omit_obvious_local_variable_types][omit_obvious_local_variable_types] lint rule.
• Add the experimental [specify_nonobvious_local_variable_types][specify_nonobvious_local_variable_types] lint rule.
• Add the experimental [avoid_futureor_void][avoid_futureor_void] lint rule.
• Add quick fixes for more than 14 diagnostics.
• Add new assists: "add digit separators", "remove digit separators", and
  "invert conditional expression".

v3.5.4

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v3.5.3

Compare Source

• Fixes an issue with the DevTools Memory tool causing OOMs. and an
  issue resulting in a missing tab bar when DevTools is embedded in
  IntelliJ and Android Studio (issue#​56607).
• Fixes an issue with the DevTools release notes showing each time
  DevTools is opened instead of only the first time (issue#​56607).
• Fixes an issue resulting in a missing tab bar when DevTools is
  embedded in IntelliJ and Android Studio (issue#​56607).

v3.5.2

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• Fixes a bug where ZLibDecoder would incorrectly attempt to decompress data
  past the end of the zlib footer (issue #​56481).
• Fixes issue where running dart from PATH could result in some commands not
  working as expected (issues #​56080, #​56306, #​56499).
• Fixes analysis server plugins not receiving setContextRoots requests or
  being provided incorrect context roots in multi-package workspaces (issue
  #​56475).

v3.5.1

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• Fixes resolving include: in analysis_options.yaml file in a nested
  folder in the workspace (issue#​56464).
• Fixes source maps generated by dart compile wasm when optimizations are
  enabled (issue #​56423).
• Fixes a bug in the dart2wasm compiler in unsound -O3 / -O4 modes where a
  implicit setter for a field of generic type will store null instead of the
  field value (issue #​56374).
• Fixes a bug in the dart2wasm compiler that can trigger in certain situations
  when using partial instantiations of generic tear-offs (constructors or static
  methods) in constant expressions (issue #​56440).
• The algorithm for computing the standard upper bound of two types,
  also known is UP, is provided the missing implementation for
  StructuralParameterType objects. In some corner cases cases the
  lacking implementation resulted in a crash of the compiler (issue #​56457).

v3.5.0

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Language

• Breaking Change #​55418: The context used by the compiler to perform
  type inference on the operand of an await expression has been changed to
  match the behavior of the analyzer. This change is not expected to make any
  difference in practice.

• Breaking Change #​55436: The context used by the compiler to perform
  type inference on the right hand side of an "if-null" expression (e1 ?? e2)
  has been changed to match the behavior of the analyzer. change is expected to
  have low impact on real-world code. But in principle it could cause
  compile-time errors or changes in runtime behavior by changing inferred
  types. The old behavior can be restored by supplying explicit types.

Libraries

dart:core

• Breaking Change #​44876: DateTime on the web platform now stores
  microseconds. The web implementation is now practically compatible with the
  native implementation, where it is possible to round-trip a timestamp in
  microseconds through a DateTime value without rounding the lower
  digits. This change might be breaking for apps that rely in some way on the
  .microsecond component always being zero, for example, expecting only three
  fractional second digits in the toString() representation. Small
  discrepancies in arithmetic due to rounding of web integers may still occur
  for extreme values, (1) microsecondsSinceEpoch outside the safe range,
  corresponding to dates with a year outside of 1685..2255, and (2) arithmetic
  (add, subtract, difference) where the Duration argument or result
  exceeds 570 years.

dart:io

• Breaking Change #​55786: SecurityContext is now final. This means
  that SecurityContext can no longer be subclassed. SecurityContext
  subclasses were never able to interoperate with other parts of dart:io.

• A ConnectionTask can now be created using an existing Future<Socket>.
  Fixes #​55562.

dart:typed_data

• Breaking Change #​53785: The unmodifiable view classes for typed data
  have been removed. These classes were deprecated in Dart 3.4.

  To create an unmodifiable view of a typed-data object, use the
  asUnmodifiableView() methods added in Dart 3.3.

• Added superinterface TypedDataList to typed data lists, implementing both
  List and TypedData. Allows abstracting over all such lists without losing
  access to either the List or the TypedData members.
  A ByteData is still only a TypedData, not a list.

dart:js_interop

• Breaking Change #​55508: importModule now accepts a JSAny instead
  of a String to support other JS values as well, like TrustedScriptURLs.

• Breaking Change #​55267: isTruthy and not now return JSBoolean
  instead of bool to be consistent with the other operators.

• Breaking Change ExternalDartReference no longer implements Object.
  ExternalDartReference now accepts a type parameter T with a bound of
  Object? to capture the type of the Dart object that is externalized.
  ExternalDartReferenceToObject.toDartObject now returns a T.
  ExternalDartReferenceToObject and ObjectToExternalDartReference are now
  extensions on T and ExternalDartReference<T>, respectively, where T extends Object?. See #​55342 and #​55536 for more details.

• Fixed some consistency issues with Function.toJS across all compilers.
  Specifically, calling Function.toJS on the same function gives you a new JS
  function (see issue #​55515), the maximum number of arguments that are
  passed to the JS function is determined by the static type of the Dart
  function, and extra arguments are dropped when passed to the JS function in
  all compilers (see #​48186).

Tools

Analyzer

• Add the [unintended_html_in_doc_comment][unintended_html_in_doc_comment] lint rule.
• Add the [invalid_runtime_check_with_js_interop_types][invalid_runtime_check_with_js_interop_types] lint rule.
• Add the [document_ignores][document_ignores] lint rule.
• Add quick fixes for more than 70 diagnostics.
• The "Add missing switch cases" quick fix now adds multiple cases, such that
  the switch becomes exhaustive.
• The "Remove const" quick fix now adds const keywords to child nodes, where
  appropriate.

Pub

• New flag dart pub downgrade --tighten to restrict lower bounds of
  dependencies' constraints to the minimum that can be resolved.

Dart Runtime

• The Dart VM only executes sound null safe code, running of unsound null
  safe code using the option --no-sound-null-safety has been removed.

• Dart_NewListOf and Dart_IsLegacyType functions are
  removed from Dart C API.

• Dart_DefaultCanonicalizeUrl is removed from the Dart C API.

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