relates to:

• SR-9839 @convention function conversions unreliably fail when type variables are introduced

Issue Description:

Unsure if this is the same issue as [SR-9839] or not, but filing separately just in case it isn't.

The following doesn't compile:

func bar(_ x: @convention(block) () -> Void) {}

func id<T>(_ x: T) -> T {
  return x
}

var qux: () -> Void = {}

bar(qux)
bar(id(qux))
bar(id(id(qux))) // error: Converting non-escaping value to 'T' may allow it to escape

However it does compile if the @convention(block) is removed from bar's parameter.