   /// provided token stream. This provides the set of expectations that the
   /// real diagnostics will be verified against.
   private static func parseExpectations(
-    url: URL, engine: DiagnosticEngine) -> Set<Expectation> {
-    var expectations = Set<Expectation>()
+    url: URL, engine: DiagnosticEngine) -> [Expectation] {
+    var expectations = [Expectation]()
     guard let input = try? String(contentsOf: url, encoding: .utf8) else {
       engine.diagnose(.couldNotReadInput(url))
       return []

  }

  /// The set of expected-{severity} comments in the file.
  let expectations: Set<Expectation>

  /// The set of diagnostics that have been parsed.
  let producedDiagnostics: [(message: Diagnostic.Message, node: Syntax?)]

                                       lineNumber: lineNum + 1) else {
        continue
      }
      expectations.append(exp)
    }
    return expectations
  }
