[SR-8536] Warn on member assignments capturing self

[CodaFi]

Previous ID	SR-8536
Radar	None
Original Reporter	@CodaFi
Type	Improvement

Additional Detail from JIRA

Votes	2
Component/s	Compiler
Labels	Improvement, StarterBug, TypeChecker
Assignee	tt (JIRA)
Priority	Medium

md5: cb331d15432b248f57b7b7bce4d077f7

Issue Description:

class Foo {
  let bar: () -> ()

  func baz() {}

  init() {
    self.bar = baz // We oughta warn about capturing 'self' implicitly.
  }
}

In the example above, we should warn about capturing `self` implicitly and, rather than suggest the user make it explicit, probably offer a fixit that provides a closure with a weak or unowned capture.

[belkadan]

Resetting assignees on all Starter Bugs that haven't been touched since 2018.

[swift-ci]

Comment by Tapan Thaker (JIRA)

Implementing this in PR 35473