Enforce @escaping for for all but the most trivial uses of captured variables.

error: nested function with an implicitly captured inout parameter can only be used as a non-escaping argument

Applied argument must be @noescape function type: %21 = argument of bb3 : $@callee_guaranteed () -> ()
A partial_apply with @inout_aliasable may only be used as a @noescape function type argument.
UNREACHABLE executed at /s/s/swift/lib/SILOptimizer/Mandatory/DiagnoseStaticExclusivity.cpp:1085!

func doit(_ f: @escaping ()->()) { f() }

public func outerFoo1(x: inout Int) {
 func innerFoo1() {
  x = 1
 }
 func innerFoo2() {
  x = 2
 }
 doit(x == 0 ? innerFoo1 : innerFoo2)
}