Sync up tuple_arguments and tuple_arguments_4 tests

Author: slavapestov

test/Compatibility/tuple_arguments_4.swift

@@ -1,7 +1,5 @@
 // RUN: %target-typecheck-verify-swift -swift-version 4
 
-// See test/Compatibility/tuple_arguments_3.swift for the Swift 3 behavior.
-
 func concrete(_ x: Int) {}
 func concreteLabeled(x: Int) {}
 func concreteTwo(_ x: Int, _ y: Int) {} // expected-note 5 {{'concreteTwo' declared here}}
@@ -1671,7 +1669,6 @@ do {
   h() // expected-error {{missing argument for parameter #1 in call}}
 }
 
-
 // https://bugs.swift.org/browse/SR-7191
 class Mappable<T> {
   init(_: T) { }

test/Constraints/tuple_arguments.swift

@@ -1671,3 +1671,12 @@ do {
   func h(_: ()) {} // expected-note {{'h' declared here}}
   h() // expected-error {{missing argument for parameter #1 in call}}
 }
+
+// https://bugs.swift.org/browse/SR-7191
+class Mappable<T> {
+  init(_: T) { }
+  func map<U>(_ body: (T) -> U) -> U { fatalError() }
+}
+
+let x = Mappable(())
+_ = x.map { (_: Void) in return () }