[NFC] Don't Store An llvm::function_ref

This class was relying on the caller to keep this member alive. In general, this will lead to startling memory ownership bugs if, say, the enumerators were returned from these functions. Pass it in as a parameter instead to formalize that contract.

Author: CodaFi

lib/AST/FrontendSourceFileDepGraphFactory.cpp

@@ -408,23 +408,17 @@ class UsedDeclEnumerator {
   /// Cache these for efficiency
   const DependencyKey sourceFileImplementation;
 
-  function_ref<void(const DependencyKey &, const DependencyKey &)> createDefUse;
-
 public:
-  UsedDeclEnumerator(
-      const SourceFile *SF, const DependencyTracker &depTracker,
-      StringRef swiftDeps,
-      function_ref<void(const DependencyKey &, const DependencyKey &)>
-          createDefUse)
+  UsedDeclEnumerator(const SourceFile *SF, const DependencyTracker &depTracker,
+                     StringRef swiftDeps)
       : SF(SF), depTracker(depTracker), swiftDeps(swiftDeps),
-        sourceFileInterface(DependencyKey::createKeyForWholeSourceFile(
-            DeclAspect::interface, swiftDeps)),
         sourceFileImplementation(DependencyKey::createKeyForWholeSourceFile(
-            DeclAspect::implementation, swiftDeps)),
-        createDefUse(createDefUse) {}
+            DeclAspect::implementation, swiftDeps)) {}
 
 public:
-  void enumerateAllUses() {
+  using UseEnumerator =
+      llvm::function_ref<void(const DependencyKey &, const DependencyKey &)>;
+  void enumerateAllUses(UseEnumerator enumerator) {
     auto &Ctx = SF->getASTContext();
     Ctx.evaluator.enumerateReferencesInFile(SF, [&](const auto &ref) {
       std::string name = ref.name.userFacingName().str();
@@ -436,36 +430,37 @@ class UsedDeclEnumerator {
       case Kind::Tombstone:
         llvm_unreachable("Cannot enumerate dead reference!");
       case Kind::TopLevel:
-        return enumerateUse<NodeKind::topLevel>("", name);
+        return enumerateUse<NodeKind::topLevel>("", name, enumerator);
       case Kind::Dynamic:
-        return enumerateUse<NodeKind::dynamicLookup>("", name);
+        return enumerateUse<NodeKind::dynamicLookup>("", name, enumerator);
       case Kind::PotentialMember: {
         std::string context = DependencyKey::computeContextForProvidedEntity<
             NodeKind::potentialMember>(nominal);
-        return enumerateUse<NodeKind::potentialMember>(context, "");
+        return enumerateUse<NodeKind::potentialMember>(context, "", enumerator);
       }
       case Kind::UsedMember: {
         std::string context =
             DependencyKey::computeContextForProvidedEntity<NodeKind::member>(
                 nominal);
-        return enumerateUse<NodeKind::member>(context, name);
+        return enumerateUse<NodeKind::member>(context, name, enumerator);
       }
       }
     });
-    enumerateExternalUses();
-    enumerateNominalUses();
+    enumerateExternalUses(enumerator);
+    enumerateNominalUses(enumerator);
   }
 
 private:
   template <NodeKind kind>
-  void enumerateUse(StringRef context, StringRef name) {
+  void enumerateUse(StringRef context, StringRef name,
+                    UseEnumerator createDefUse) {
     // Assume that what is depended-upon is the interface
     createDefUse(
         DependencyKey(kind, DeclAspect::interface, context.str(), name.str()),
         sourceFileImplementation);
   }
 
-  void enumerateNominalUses() {
+  void enumerateNominalUses(UseEnumerator enumerator) {
     auto &Ctx = SF->getASTContext();
     Ctx.evaluator.enumerateReferencesInFile(SF, [&](const auto &ref) {
       const NominalTypeDecl *subject = ref.subject;
@@ -476,26 +471,26 @@ class UsedDeclEnumerator {
       std::string context =
           DependencyKey::computeContextForProvidedEntity<NodeKind::nominal>(
               subject);
-      enumerateUse<NodeKind::nominal>(context, "");
+      enumerateUse<NodeKind::nominal>(context, "", enumerator);
     });
   }
 
-  void enumerateExternalUses() {
+  void enumerateExternalUses(UseEnumerator enumerator) {
     for (StringRef s : depTracker.getIncrementalDependencies())
-      enumerateUse<NodeKind::incrementalExternalDepend>("", s);
+      enumerateUse<NodeKind::incrementalExternalDepend>("", s, enumerator);
 
     for (StringRef s : depTracker.getDependencies())
-      enumerateUse<NodeKind::externalDepend>("", s);
+      enumerateUse<NodeKind::externalDepend>("", s, enumerator);
   }
 };
 } // end namespace
 
 void FrontendSourceFileDepGraphFactory::addAllUsedDecls() {
-  UsedDeclEnumerator(SF, depTracker, swiftDeps,
-                     [&](const DependencyKey &def, const DependencyKey &use) {
-                       addAUsedDecl(def, use);
-                     })
-    .enumerateAllUses();
+  UsedDeclEnumerator(SF, depTracker, swiftDeps)
+      .enumerateAllUses(
+          [&](const DependencyKey &def, const DependencyKey &use) {
+            addAUsedDecl(def, use);
+          });
 }
 
 //==============================================================================