v3.6.0

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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".