[Tests] NFC: Add more test-cases that were previously solved due to old hacks behavior

test/Constraints/old_hack_related_ambiguities.swift

@@ -61,3 +61,120 @@ do {
   }
 }
 
+// ambiguities related to ~=
+protocol _Error: Error {}
+
+extension _Error {
+  public static func ~=(lhs: Self, rhs: Self) -> Bool {
+    false
+  }
+
+  public static func ~=(lhs: Error, rhs: Self) -> Bool {
+    false
+  }
+
+  public static func ~=(lhs: Self, rhs: Error) -> Bool {
+    false
+  }
+}
+
+enum CustomError {
+  case A
+}
+
+extension CustomError: _Error {}
+
+func f(e: CustomError) {
+  if e ~= CustomError.A {}
+}
+
+// Generic overload should be preferred over concrete one because the latter is non-default literal
+struct Pattern {}
+
+func ~= (pattern: Pattern, value: String) -> Bool {
+  return false
+}
+
+extension Pattern: ExpressibleByStringLiteral {
+  init(stringLiteral value: String) {}
+}
+
+func test_default_tilda(v: String) {
+  _ = "hi" ~= v // Ok
+}
+
+struct UUID {}
+
+struct LogKey {
+  init(base: some CustomStringConvertible, foo: Int = 0) {
+  }
+
+  init(base: UUID, foo: Int = 0) {
+  }
+}
+
+@available(swift 99)
+extension LogKey {
+  init(base: String?) {
+  }
+
+  init(base: UUID?) {
+  }
+}
+
+func test_that_unavailable_init_is_not_used(x: String?) {
+  _ = LogKey(base: x ?? "??")
+}
+
+// error: value of optional type 'UID?' must be unwrapped to a value of type 'UID'
+struct S: Comparable {
+  static func <(lhs: Self, rhs: Self) -> Bool {
+    false
+  }
+}
+
+func max(_ a: S?, _ b: S?) -> S? {
+  nil
+}
+
+func test_stdlib_max_selection(s: S) -> S {
+  let new = max(s, s)
+  return new // Ok
+}
+
+// error: initializer for conditional binding must have Optional type, not 'UnsafeMutablePointer<Double>'
+do {
+  struct TestPointerConversions {
+    var p: UnsafeMutableRawPointer { get { fatalError() } }
+
+    func f(_ p: UnsafeMutableRawPointer) {
+      guard let x = UnsafeMutablePointer<Double>(OpaquePointer(self.p)) else {
+        return
+      }
+      _ = x
+
+      guard let x = UnsafeMutablePointer<Double>(OpaquePointer(p)) else {
+        return
+      }
+      _ = x
+    }
+  }
+}
+
+// error: initializer 'init(_:)' requires that 'T' conform to 'BinaryInteger'
+do {
+  struct Config {
+    subscript<T>(_ key: String) -> T? { nil }
+    subscript(_ key: String) -> Any? { nil }
+  }
+
+  struct S {
+	  init(maxQueueDepth: UInt) {}
+  }
+
+  func f(config: Config) {
+    let maxQueueDepth = config["hi"] ?? 256
+    _ = S(maxQueueDepth: UInt(maxQueueDepth))
+  }
+}
+