Const typed data (Int8List, et al.)

[a-siva]

e.g:

const Int8Array int8 = const [10, 100];

does not work, instead we need to write code as follows:
Int8Array initInt8Array() {
  var list = new Int8Array(2);
  list[0] = 10;
  list[1] = 100;
  return list;
}
Int8Array int8 = initInt8Array();

We should try and make it possible to initialize constant scalar lists
similar to how we initialize all lists.

[sethladd]

Siva,

Running in production mode, that code is:

const var int8 = const [10, 100];

Looks like you're asking for a new literal for scalar lists?

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Added Triaged label.

[lrhn]

It could be handled by a const constructor on Uint8List that takes a const List<int> as argument. It will require compiler magic to actually become a real Uint8List, and I don't see it happening any time soon.
I'd recommend just using
  new Int8List.from(const [10, 100]);
or just use:
  const [10, 100]
directly (it won't be a Int8List, but it will be a list, and the system could decide to have an efficient implementation of a constant list of small integers).

[lrhn]

Removed Type-Defect label.
Added Type-Enhancement, Library-TypedData labels.

[floitschG]

Set owner to @lrhn.

[lrhn]

Creating a const typed-data list is not a library issue - it needs language support.

For one thing, all type-data lists are currently mutable. Maybe if we had an immutable ByteBuffer, it would make more sense.

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Removed the owner.
Removed Area-Library, Library-TypedData labels.
Added Area-Language label.

[munificent]

Not unreasonable, but not planned either. The set of classes and operations that could be usefully made const is potentially unbounded and it's hard to decide what makes the cut and what doesn't. At least for now, we don't have any intention of including typed_data's types in it.

[truongsinh]

any update for const typed data, is it still unplanned for the time being?

[lrhn]

There are still no current plans.

[truongsinh]

So const a = [4,3,5] and final b = Uint8List.fromList([4,3,5]) which one is more preferred, or does it depend on scenarios? I understand that the reason we have typed data in the first place is for performance (time and space), but I assume having a compile-time const also has it's advantages.

[truongsinh]

@munificent @lrhn any recommendation for performance junkies?

[lrhn]

For performance, I'd definitely go with:

final b = Uint8List(3)..[0] = 4..[1] = 3..[2] = 5;

If I could trust the compiler to optimize Uint8List.from(listLiteral), then that would be nice. Until then I'd avoid the extra allocation and iteration.

Creating and populating a Uint8List increases code-size.
A const list may or may not increase code size or memory pressure, depending on how it's implemented.

Also consider:

final b = "\x04\x03\x05".codeUnits; 

👿