Make the `value` fields of `BoxedInt`, `BoxedDouble` and `BoxedBool`
`final`, to generate immutable Wasm fields for them.
Immutable fields can potentially generate better code, as loads from the
same object will always generate the same value.
To allow making the `value` fields `final`, add a constructor.
To allow adding a constructor, "implement` base classes instead of
extending them. With `extends` the front-end wants us to call the
superclass constructors, even though they don't have any constructors.
Implementing `bool` (instead of extending) causes issues in TFA as it
currently assumes bool literals are compiled as the `bool` class. Update
TFA to treat bool literals the same way as `int` and `double` literals.
Tested: existing tests
Change-Id: I3282e188d784fa7a22421edc79ed47f9d85faf19
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/393320
Commit-Queue: Ömer Ağacan <omersa@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
Ömer Sinan Ağacan
af2bea8162