[test] Substring: remove unnecessary expected arguments

The previous commit made these redundant.

Author: lorentey

Diff for: test/stdlib/subString.swift

@@ -12,22 +12,17 @@ func checkMatch<S: Collection, T: Collection>(_ x: S, _ y: T, _ i: S.Index)
   expectEqual(x[i], y[i])
 }
 
-func checkMatchContiguousStorage<S: Collection, T: Collection>(_ x: S, _ y: T, expected: Bool)
+func checkMatchContiguousStorage<S: Collection, T: Collection>(_ x: S, _ y: T)
   where S.Element == T.Element, S.Element: Equatable
 {
   let xElement = x.withContiguousStorageIfAvailable { $0.first }
   let yElement = y.withContiguousStorageIfAvailable { $0.first }
 
-  if expected {
-    expectEqual(xElement, yElement)
-  } else {
-    expectNotEqual(xElement, yElement)
-  }
+  expectEqual(xElement, yElement)
 }
 
-func checkHasContiguousStorage<S: Collection>(_ x: S, expected: Bool) {
-  let hasStorage = x.withContiguousStorageIfAvailable { _ in true } ?? false
-  expectEqual(hasStorage, expected)
+func checkHasContiguousStorage<S: Collection>(_ x: S) {
+  expectTrue(x.withContiguousStorageIfAvailable { _ in true } ?? false)
 }
 
 func checkHasContiguousStorageSubstring(_ x: Substring.UTF8View) {
@@ -252,21 +247,21 @@ SubstringTests.test("UTF8View") {
     expectEqual("", String(u.dropFirst(100))!)
     expectEqual("", String(u.dropLast(100))!)
 
-    checkHasContiguousStorage(s.utf8, expected: true) // Strings always do
+
+    checkHasContiguousStorage(s.utf8) // Strings always do
     checkHasContiguousStorageSubstring(t)
     checkHasContiguousStorageSubstring(u)
-    checkMatchContiguousStorage(Array(s.utf8), s.utf8, expected: true)
+    checkMatchContiguousStorage(Array(s.utf8), s.utf8)
 
     // The specialization for Substring.withContiguousStorageIfAvailable was
     // added in https://github.com/apple/swift/pull/29146.
     guard #available(macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, *) else {
       return
     }
-
-    checkHasContiguousStorage(t, expected: true)
-    checkHasContiguousStorage(u, expected: true)
-    checkMatchContiguousStorage(Array(t), t, expected: true)
-    checkMatchContiguousStorage(Array(u), u, expected: true)
+    checkHasContiguousStorage(t)
+    checkHasContiguousStorage(u)
+    checkMatchContiguousStorage(Array(t), t)
+    checkMatchContiguousStorage(Array(u), u)
   }
 }