Address review.

Author: David Ungar

Sources/SwiftDriver/IncrementalCompilation/ModuleDependencyGraph.swift

@@ -377,10 +377,11 @@ extension ModuleDependencyGraph {
   private func indiscriminatelyFindNodesInvalidated(
     by integrand: ExternalIntegrand
   ) -> DirectlyInvalidatedNodeSet {
-    if let reason = whyIndiscriminatelyFindNodesInvalidated(by: integrand) {
-      return collectUntracedNodes(thatUse: integrand.externalDependency, reason)
+    guard let reason = whyIndiscriminatelyFindNodesInvalidated(by: integrand)
+    else {
+      return DirectlyInvalidatedNodeSet()
     }
-    return DirectlyInvalidatedNodeSet()
+    return collectUntracedNodes(thatUse: integrand.externalDependency, reason)
   }
 
   /// Figure out the reason to integrate, (i.e. process) a dependency that will be read and integrated.
@@ -455,7 +456,7 @@ extension ModuleDependencyGraph {
   ///
   /// If not using incremental imports, a given build may have to invalidate nodes more than once for the same `swiftmodule`:
   /// For example, on a clean build, as each initial `swiftdeps` is integrated, if the file uses a changed `swiftmodule`,
-  /// iit must be scheduled for recompilation. Thus invalidation happens for every dependent input file.
+  /// it must be scheduled for recompilation. Thus invalidation happens for every dependent input file.
   fileprivate struct ExternalDependencyCurrencyCache {
     private let fileSystem: FileSystem
     private let buildStartTime: Date

Tests/IncrementalTestFramework/CompiledSourceCollector.swift

@@ -21,7 +21,6 @@ import TestUtilities
 /// - seealso: Test
 struct CompiledSourceCollector {
   private var collectedCompiledBasenames = [String]()
-  private var collectedReadDependenciesInOrder = [String]()
   private var collectedReadDependencies = Set<String>()
 
   private func getCompiledBasenames(from d: Diagnostic) -> [String] {
@@ -50,7 +49,6 @@ struct CompiledSourceCollector {
   }
 
   private mutating func appendReadDependency(_ dep: String) {
-    collectedReadDependenciesInOrder.append(dep)
     let wasNew = collectedReadDependencies.insert(dep).inserted
     guard wasNew || dep.hasSuffix(FileType.swift.rawValue)
     else {