[CSSimplify] Attempt property wrapper fix after restrictions

[theblixguy]

The following code:

struct User {}

@propertyWrapper struct Wrapper<T> {
  var wrappedValue: T
}

class Test {
  @Wrapper var user: User?
}

func genericFunc<T>(_ argument: T?) -> T? {
  return argument
}

let test = Test()
genericFunc(test.user)

fails to compile with a very strange error - cannot convert value 'user' of type 'User?' to expected type 'Wrapper<User?>?', use wrapper instead.

This seems to be because we're attempting property wrapper fix (and creating subtype constraints) before we've given simplifyRestrictedConstraintImpl a chance to handle any restrictions. So, delay the attempt to create a fix so restrictions can be handled first.

Resolves SR-11654, SR-12233
Resolves rdar://problem/56543018

[xedin]

Thank you!

[theblixguy]

@swift-ci please smoke test

[theblixguy]

@xedin Is this worth cherry-picking to 5.2? :)

[xedin]

I think it might be too late already, but I'll double-check...

[xedin]

Yeah, unfortunately no more 5.2 changes are accepted at this point.

[theblixguy]

@xedin Okay, no worries :)