Initial support for @_objcImpl stored properties

No runtime tests yet.

Author: beccadax

include/swift/AST/DeclContext.h

@@ -507,6 +507,11 @@ class alignas(1 << DeclContextAlignInBits) DeclContext
   LLVM_READONLY
   DeclContext *getModuleScopeContext() const;
 
+  /// If this DeclContext is an \c \@_objcImplementation extension, returns the
+  /// \c DeclContext for the Objective-C declaration it implements. Otherwise
+  /// returns \c this.
+  DeclContext *getImplementedObjCContext() const;
+
   /// Returns the source file that contains this context, or null if this
   /// is not within a source file.
   LLVM_READONLY

lib/AST/DeclContext.cpp

@@ -303,6 +303,13 @@ DeclContext *DeclContext::getModuleScopeContext() const {
   }
 }
 
+DeclContext *DeclContext::getImplementedObjCContext() const {
+  if (auto ED = dyn_cast<ExtensionDecl>(this))
+    if (auto impl = dyn_cast_or_null<DeclContext>(ED->getImplementedObjCDecl()))
+      return impl;
+  return const_cast<DeclContext *>(this);
+}
+
 void DeclContext::getSeparatelyImportedOverlays(
     ModuleDecl *declaring, SmallVectorImpl<ModuleDecl *> &overlays) const {
   if (auto SF = getParentSourceFile())

lib/IRGen/GenClass.cpp

@@ -223,7 +223,8 @@ namespace {
                                bool superclass) {
       if (theClass->hasClangNode() && !theClass->isForeignReferenceType()) {
         Options |= ClassMetadataFlags::ClassHasObjCAncestry;
-        return;
+        if (!theClass->getObjCImplementationDecl())
+          return;
       }
 
       if (theClass->isNativeNSObjectSubclass()) {

lib/IRGen/GenMeta.cpp

@@ -3833,6 +3833,9 @@ namespace {
       : super(IGM, theClass, builder, fieldLayout) {}
 
     void addFieldOffset(VarDecl *var) {
+      if (FieldLayout.hasObjCImplementation())
+        return;
+
       addFixedFieldOffset(IGM, B, var, [](DeclContext *dc) {
         return dc->getDeclaredTypeInContext();
       });
@@ -3869,12 +3872,18 @@ namespace {
       : super(IGM, theClass, builder, fieldLayout) {}
 
     void addFieldOffset(VarDecl *var) {
+      if (FieldLayout.hasObjCImplementation())
+        return;
+
       // Field offsets are either copied from the superclass or calculated
       // at runtime.
       B.addInt(IGM.SizeTy, 0);
     }
 
     void addFieldOffsetPlaceholders(MissingMemberDecl *placeholder) {
+      if (FieldLayout.hasObjCImplementation())
+        return;
+
       for (unsigned i = 0,
                     e = placeholder->getNumberOfFieldOffsetVectorEntries();
            i < e; ++i) {
@@ -4334,6 +4343,9 @@ namespace {
     }
 
     void addFieldOffset(VarDecl *var) {
+      if (FieldLayout.hasObjCImplementation())
+        return;
+
       addFixedFieldOffset(IGM, B, var, [&](DeclContext *dc) {
         return dc->mapTypeIntoContext(type);
       });

lib/IRGen/Linking.cpp

@@ -703,7 +703,8 @@ SILLinkage LinkEntity::getLinkage(ForDefinition_t forDefinition) const {
     auto linkage = getDeclLinkage(varDecl);
 
     // Classes with resilient storage don't expose field offset symbols.
-    if (cast<ClassDecl>(varDecl->getDeclContext())->isResilient()) {
+    auto implContext = varDecl->getDeclContext()->getImplementedObjCContext();
+    if (cast<ClassDecl>(implContext)->isResilient()) {
       assert(linkage != FormalLinkage::PublicNonUnique &&
             "Cannot have a resilient class with non-unique linkage");
 

lib/IRGen/MetadataLayout.cpp

@@ -366,7 +366,8 @@ ClassMetadataLayout::ClassMetadataLayout(IRGenModule &IGM, ClassDecl *decl)
     }
 
     void addFieldOffset(VarDecl *field) {
-      assert(IsInTargetFields == (field->getDeclContext() == Target));
+      assert(IsInTargetFields ==
+              (field->getDeclContext()->getImplementedObjCContext() == Target));
       if (IsInTargetFields) {
         ++Layout.NumImmediateMembers;
         Layout.FieldOffsets.try_emplace(field, getNextOffset());
@@ -382,7 +383,7 @@ ClassMetadataLayout::ClassMetadataLayout(IRGenModule &IGM, ClassDecl *decl)
     }
 
     void addFieldOffsetPlaceholders(MissingMemberDecl *placeholder) {
-      if (placeholder->getDeclContext() == Target) {
+      if (placeholder->getDeclContext()->getImplementedObjCContext() == Target) {
         Layout.NumImmediateMembers +=
           placeholder->getNumberOfFieldOffsetVectorEntries();
       }

lib/SIL/Verifier/SILVerifier.cpp

@@ -3282,7 +3282,8 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
                              F.getResilienceExpansion()),
             "cannot access storage of resilient class");
 
-    require(EI->getField()->getDeclContext() == cd,
+    require(EI->getField()->getDeclContext() ==
+                cd->getImplementationContext()->getAsGenericContext(),
             "ref_element_addr field must be a member of the class");
 
     if (EI->getModule().getStage() != SILStage::Lowered) {

lib/SILGen/SILGenType.cpp

@@ -1230,6 +1230,10 @@ class SILGenExtension : public TypeMemberVisitor<SILGenExtension> {
 
   /// Emit SIL functions for all the members of the extension.
   void emitExtension(ExtensionDecl *e) {
+    // Arguably, we should divert to SILGenType::emitType() here if it's an
+    // @_objcImplementation extension, but we don't actually need to do any of
+    // the stuff that it currently does.
+
     for (Decl *member : e->getABIMembers())
       visit(member);
 
@@ -1305,6 +1309,17 @@ class SILGenExtension : public TypeMemberVisitor<SILGenExtension> {
 
   void visitVarDecl(VarDecl *vd) {
     if (vd->hasStorage()) {
+      if (!vd->isStatic()) {
+        // Is this a stored property of an @_objcImplementation extension?
+        auto ed = cast<ExtensionDecl>(vd->getDeclContext());
+        if (auto cd =
+                dyn_cast_or_null<ClassDecl>(ed->getImplementedObjCDecl())) {
+          // Act as though we declared it on the class.
+          SILGenType(SGM, cd).visitVarDecl(vd);
+          return;
+        }
+      }
+
       bool hasDidSetOrWillSetDynamicReplacement =
           vd->hasDidSetOrWillSetDynamicReplacement();
       assert((vd->isStatic() || hasDidSetOrWillSetDynamicReplacement) &&

test/IRGen/Inputs/objc_implementation.h

@@ -2,6 +2,8 @@
 
 @interface ImplClass: NSObject
 
+@property (assign) int implProperty;
+
 - (void)mainMethod:(int)param;
 
 @end