Make result type of expectations optional for consistency with #780

Sources/Testing/ExitTests/ExitTest.swift

@@ -236,7 +236,7 @@ func callExitTest(
   isRequired: Bool,
   isolation: isolated (any Actor)? = #isolation,
   sourceLocation: SourceLocation
-) async -> Result<ExitTestArtifacts, any Error> {
+) async -> Result<ExitTestArtifacts?, any Error> {
   guard let configuration = Configuration.current ?? Configuration.all.first else {
     preconditionFailure("A test must be running on the current task to use #expect(exitsWith:).")
   }

Sources/Testing/Expectations/ExpectationChecking+Macro.swift

@@ -1149,7 +1149,7 @@ public func __checkClosureCall(
   isRequired: Bool,
   isolation: isolated (any Actor)? = #isolation,
   sourceLocation: SourceLocation
-) async -> Result<ExitTestArtifacts, any Error> {
+) async -> Result<ExitTestArtifacts?, any Error> {
   await callExitTest(
     exitsWith: expectedExitCondition,
     observing: observedValues,

Sources/Testing/Support/Additions/ResultAdditions.swift

@@ -15,19 +15,32 @@ extension Result {
   ///   `#require()` macros. Do not call it directly.
   @inlinable public func __expected() where Success == Void {}
 
+  /// Handle this instance as if it were returned from a call to `#require()`.
+  ///
+  /// - Warning: This function is used to implement the `#expect()` and
+  ///   `#require()` macros. Do not call it directly.
+  @inlinable public func __required() throws -> Success {
+    try get()
+  }
+}
+
+// MARK: - Optional success values
+
+extension Result {
   /// Handle this instance as if it were returned from a call to `#expect()`.
   ///
   /// - Warning: This function is used to implement the `#expect()` and
   ///   `#require()` macros. Do not call it directly.
-  @inlinable public func __expected() -> Success? {
+  @inlinable public func __expected<T>() -> Success where Success == T? {
     try? get()
   }
 
   /// Handle this instance as if it were returned from a call to `#require()`.
   ///
   /// - Warning: This function is used to implement the `#expect()` and
   ///   `#require()` macros. Do not call it directly.
-  @inlinable public func __required() throws -> Success {
-    try get()
+  @inlinable public func __required<T>() throws -> T where Success == T? {
+    // TODO: handle edge case where the value is nil (see #780)
+    try get()!
   }
 }