ConformanceLookupTable: Recursively inherit into subclasses when incrementally adding extension conformances.

Previously, we would only reliably propagate conformances from new extensions to immediate subclasses, since when we visit grandchild classes, we'd see no change in the immediate base class's status. Fix this by walking up the entire superclass chain when we look for new inherited conformances, and track the last processed state of different nominal type decls' extensions separately. Fixes SR-1480.

Author: jckarter

include/swift/AST/Decl.h

@@ -3203,6 +3203,10 @@ class ClassDecl : public NominalTypeDecl {
   /// Retrieve the superclass of this class, or null if there is no superclass.
   Type getSuperclass() const { return LazySemanticInfo.Superclass.getPointer(); }
 
+  /// Retrieve the ClassDecl for the superclass of this class, or null if there
+  /// is no superclass.
+  ClassDecl *getSuperclassDecl() const;
+
   /// Set the superclass of this class.
   void setSuperclass(Type superclass) {
     LazySemanticInfo.Superclass.setPointerAndInt(superclass, true);

include/swift/AST/TypeAlignments.h

@@ -33,6 +33,7 @@ namespace swift {
   class Decl;
   class DeclContext;
   class Expr;
+  class ExtensionDecl;
   class GenericTypeParamDecl;
   class NormalProtocolConformance;
   class OperatorDecl;
@@ -80,6 +81,7 @@ LLVM_DECLARE_TYPE_ALIGNMENT(swift::GenericTypeParamDecl, swift::DeclAlignInBits)
 LLVM_DECLARE_TYPE_ALIGNMENT(swift::OperatorDecl, swift::DeclAlignInBits)
 LLVM_DECLARE_TYPE_ALIGNMENT(swift::ProtocolDecl, swift::DeclAlignInBits)
 LLVM_DECLARE_TYPE_ALIGNMENT(swift::ValueDecl, swift::DeclAlignInBits)
+LLVM_DECLARE_TYPE_ALIGNMENT(swift::ExtensionDecl, swift::DeclAlignInBits)
 
 LLVM_DECLARE_TYPE_ALIGNMENT(swift::TypeBase, swift::TypeAlignInBits)
 LLVM_DECLARE_TYPE_ALIGNMENT(swift::ArchetypeType, swift::TypeAlignInBits)

lib/AST/ConformanceLookupTable.cpp

@@ -141,9 +141,10 @@ void ConformanceLookupTable::forEachInStage(ConformanceStage stage,
                                             ExtensionFunc extensionFunc) {
   assert(static_cast<unsigned>(stage) < NumConformanceStages &&
          "NumConformanceStages has not been updated");
-  LastProcessedEntry &lastProcessed
-    = LastProcessed[static_cast<unsigned>(stage)];
 
+  LastProcessedEntry &lastProcessed
+    = LastProcessed[nominal][static_cast<unsigned>(stage)];
+  
   // Handle the nominal type.
   if (!lastProcessed.getInt()) {
     lastProcessed.setInt(true);
@@ -300,23 +301,26 @@ void ConformanceLookupTable::updateLookupTable(NominalTypeDecl *nominal,
       if (resolver)
         resolver->resolveSuperclass(classDecl);
 
-      if (Type superclass = classDecl->getSuperclass()) {
-        if (auto superclassDecl 
-              = superclass->getClassOrBoundGenericClass()) {
-          // Break infinite recursion when visiting ill-formed classes
-          // with circular inheritance.
-          if (VisitingSuperclass)
-            return;
-          llvm::SaveAndRestore<bool> visiting(VisitingSuperclass, true);
-
-          // Resolve the conformances of the superclass.
-          superclassDecl->prepareConformanceTable();
-          superclassDecl->ConformanceTable->updateLookupTable(
-            superclassDecl,
-            ConformanceStage::Resolved,
-            resolver);
-          
-          // Expand inherited conformances.
+      if (auto superclassDecl = classDecl->getSuperclassDecl()) {
+        // Break infinite recursion when visiting ill-formed classes
+        // with circular inheritance.
+        if (VisitingSuperclass)
+          return;
+        llvm::SaveAndRestore<bool> visiting(VisitingSuperclass, true);
+
+        // Resolve the conformances of the superclass.
+        superclassDecl->prepareConformanceTable();
+        superclassDecl->ConformanceTable->updateLookupTable(
+          superclassDecl,
+          ConformanceStage::Resolved,
+          resolver);
+        
+        // Expand inherited conformances from all superclasses.
+        // We may have circular inheritance in ill-formed classes, so keep an
+        // eye out for that.
+        auto circularSuperclass = superclassDecl->getSuperclassDecl();
+        
+        do {
           forEachInStage(stage, superclassDecl, resolver,
                          [&](NominalTypeDecl *superclass) {
                            inheritConformances(classDecl, superclassDecl,
@@ -326,7 +330,12 @@ void ConformanceLookupTable::updateLookupTable(NominalTypeDecl *nominal,
                            inheritConformances(classDecl, superclassDecl, ext,
                                                resolver);
                          });
-        }
+          superclassDecl = superclassDecl->getSuperclassDecl();
+          if (circularSuperclass)
+            circularSuperclass = circularSuperclass->getSuperclassDecl();
+          if (circularSuperclass)
+            circularSuperclass = circularSuperclass->getSuperclassDecl();
+        } while (superclassDecl != circularSuperclass);
       }
     }
     break;    
@@ -742,11 +751,11 @@ DeclContext *ConformanceLookupTable::getConformingContext(
       return nullptr;
 
     // If we had a circular dependency, the superclass may not exist.
-    if (!classDecl->getSuperclass())
-      return nullptr;
-        
     auto superclassDecl
-      = classDecl->getSuperclass()->getClassOrBoundGenericClass();
+      = classDecl->getSuperclassDecl();
+    
+    if (!superclassDecl)
+      return nullptr;
 
     if (!classDecl->ConformanceTable->VisitingSuperclass) {
       llvm::SaveAndRestore<bool> visiting(

lib/AST/ConformanceLookupTable.h

@@ -27,6 +27,7 @@
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/PointerUnion.h"
 #include "llvm/ADT/SetVector.h"
+#include <unordered_map>
 
 namespace swift {
 
@@ -67,11 +68,16 @@ class ConformanceLookupTable {
   /// at that stage.
   typedef llvm::PointerIntPair<ExtensionDecl *, 1, bool> LastProcessedEntry;
 
-  /// Array indicating how far we have gotten in processing the
+  /// Array indicating how far we have gotten in processing each
   /// nominal type and list of extensions for each stage of
   /// conformance checking.
-  LastProcessedEntry LastProcessed[NumConformanceStages];
-
+  ///
+  /// Uses std::unordered_map instead of DenseMap so that stable interior
+  /// references can be taken.
+  std::unordered_map<NominalTypeDecl *,
+                     std::array<LastProcessedEntry, NumConformanceStages>>
+  LastProcessed;
+  
   /// The list of parsed extension declarations that have been delayed because
   /// no resolver was available at the time.
   ///

lib/AST/Decl.cpp

@@ -4677,3 +4677,9 @@ Type TypeBase::getSwiftNewtypeUnderlyingType() {
 
   return {};
 }
+
+ClassDecl *ClassDecl::getSuperclassDecl() const {
+  if (auto superclass = getSuperclass())
+    return superclass->getClassOrBoundGenericClass();
+    return nullptr;
+}

test/decl/ext/Inputs/extension-inheritance-conformance-objc-multi-file-2.swift

@@ -0,0 +1,2 @@
+extension Responder {}
+extension View {}

test/decl/ext/Inputs/extension-inheritance-conformance-objc.h

@@ -0,0 +1,11 @@
+__attribute__((objc_root_class))
+@interface Object
++alloc;
+-init;
+@end
+
+@interface Responder: Object
+@end
+
+@interface View: Responder
+@end

test/decl/ext/extension-inheritance-conformance-native.swift

@@ -0,0 +1,20 @@
+// RUN: %target-swift-frontend -parse -verify %s
+
+class Object {}
+class Responder: Object {}
+class View: Responder {}
+
+extension View {}
+
+protocol Foo {}
+
+extension Foo {
+  func bar() -> Self { return self }
+}
+
+extension Object: Foo {}
+
+_ = Object().bar()
+_ = Responder().bar()
+_ = View().bar()
+

test/decl/ext/extension-inheritance-conformance-objc-multi-file.swift

@@ -0,0 +1,19 @@
+// RUN: %target-swift-frontend -import-objc-header %S/Inputs/extension-inheritance-conformance-objc.h -parse -verify -primary-file %s %S/Inputs/extension-inheritance-conformance-objc-multi-file-2.swift
+// RUN: %target-swift-frontend -import-objc-header %S/Inputs/extension-inheritance-conformance-objc.h -parse -verify %s -primary-file %S/Inputs/extension-inheritance-conformance-objc-multi-file-2.swift
+// RUN: %target-swift-frontend -import-objc-header %S/Inputs/extension-inheritance-conformance-objc.h -parse -verify -primary-file %S/Inputs/extension-inheritance-conformance-objc-multi-file-2.swift %s
+// RUN: %target-swift-frontend -import-objc-header %S/Inputs/extension-inheritance-conformance-objc.h -parse -verify %S/Inputs/extension-inheritance-conformance-objc-multi-file-2.swift -primary-file %s
+
+// REQUIRES: objc_interop
+
+protocol Foo {}
+
+extension Foo {
+  func bar() -> Self { return self }
+}
+
+extension Object: Foo {}
+
+let x = Object().bar()
+let y = Responder().bar()
+let z = View().bar()
+

test/decl/ext/extension-inheritance-conformance-objc.swift

@@ -0,0 +1,18 @@
+// RUN: %target-swift-frontend -import-objc-header %S/Inputs/extension-inheritance-conformance-objc.h -parse -verify %s
+
+// REQUIRES: objc_interop
+
+extension View {}
+
+protocol Foo {}
+
+extension Foo {
+  func bar() -> Self { return self }
+}
+
+extension Object: Foo {}
+
+_ = Object().bar()
+_ = Responder().bar()
+_ = View().bar()
+