Pattern destructuring could enable calling FunctionTypes

[FMorschel]

Today we have patterns that allow us to deconstruct a variable:

class Class {
  int myField = 0;
}

void foo() {
  var instance = Class();
  if (instance case Class(myField: var myFieldValue)) {}
}

I think of this structure like:

//    getter assigns to variable
Class(myField: var myFieldValue)

Basically the = operator but swapped:

var myFieldValue = instance.myField;

---

We also can get a method as a FunctionType:

class Class {
  int foo() => 0;
}

void foo() {
  var instance = Class();
  if (instance case Class(foo: var fooFn)) {
    fooFn(3);
  }
}

---

I'd like to request a change in that we could:

if (instance case Class(foo(3): var fooValue)) {

And for Future we could add await before var like:

class Class {
  Future<int> foo() async => 0;
}

void foo() async {
  var instance = Class();
  if (instance case Class(foo(3): await var fooValue)) {
    print(fooValue);
  }
}

[FMorschel]

I don't expect this to be used on methods that contain many arguments since that would become harder to read, but I feel like this could help with small ones avoing another line.

[lrhn]

We also can get a method as a FunctionType:

Not absolutely sure that's intended, but will have to check the future specification to be sure whether it's allowed by that.

Edit: I checked, it's intended to work.
Don't know why, but it's there.

I'd like to request a change in that we could:

if (instance case Class(foo(3): var fooValue)) {

So would I: #2433

For allowing await, combine that with #25

[munificent]

If I understand the proposal here correctly, I think it's pretty much a duplicate of #2433, so I'm going to go ahead and close this one. If I'm wrong, let me know and we can reopen it.