diff --git a/include/swift/AST/Decl.h b/include/swift/AST/Decl.h
index c2afe755da23e..5ae75346d4cbc 100644
--- a/include/swift/AST/Decl.h
+++ b/include/swift/AST/Decl.h
@@ -4592,6 +4592,23 @@ class AbstractStorageDecl : public ValueDecl {
   /// with caution.
   AccessorDecl *getSynthesizedAccessor(AccessorKind kind) const;
 
+  /// Return an accessor part of the set of opaque accessors dictated by the
+  /// requirements of the ABI.
+  ///
+  /// This will synthesize the accessor if one is required but not specified
+  /// in source; for example, most of the time a mutable property is required
+  /// to have a 'modify' accessor, but if the property was only written with
+  /// 'get' and 'set' accessors, 'modify' will be synthesized to call 'get'
+  /// followed by 'set'.
+  ///
+  /// If the accessor is not needed for ABI reasons, this returns nullptr.
+  /// To ensure an accessor is always returned, use getSynthesizedAccessor().
+  AccessorDecl *getOpaqueAccessor(AccessorKind kind) const;
+
+  /// Return an accessor that was written in source. Returns null if the
+  /// accessor was not explicitly defined by the user.
+  AccessorDecl *getParsedAccessor(AccessorKind kind) const;
+
   /// Visit all the opaque accessors that this storage is expected to have.
   void visitExpectedOpaqueAccessors(
                             llvm::function_ref<void (AccessorKind)>) const;
diff --git a/lib/AST/ASTPrinter.cpp b/lib/AST/ASTPrinter.cpp
index fa96df6a70bcc..0c087d79645c4 100644
--- a/lib/AST/ASTPrinter.cpp
+++ b/lib/AST/ASTPrinter.cpp
@@ -1804,7 +1804,7 @@ void PrintAST::printAccessors(const AbstractStorageDecl *ASD) {
   if ((PrintAbstract || isGetSetImpl()) &&
       !Options.PrintGetSetOnRWProperties &&
       !Options.FunctionDefinitions &&
-      !ASD->getAccessor(AccessorKind::Get)->isMutating() &&
+      !ASD->isGetterMutating() &&
       !ASD->getAccessor(AccessorKind::Set)->isExplicitNonMutating()) {
     return;
   }
diff --git a/lib/AST/ASTVerifier.cpp b/lib/AST/ASTVerifier.cpp
index 9a2828d401e1d..6abc0e3acde5e 100644
--- a/lib/AST/ASTVerifier.cpp
+++ b/lib/AST/ASTVerifier.cpp
@@ -1876,7 +1876,7 @@ class Verifier : public ASTWalker {
       if (auto *baseIOT = E->getBase()->getType()->getAs<InOutType>()) {
         if (!baseIOT->getObjectType()->is<ArchetypeType>()) {
           auto *VD = dyn_cast<VarDecl>(E->getMember().getDecl());
-          if (!VD || VD->getAllAccessors().empty()) {
+          if (!VD || !VD->requiresOpaqueAccessors()) {
             Out << "member_ref_expr on value of inout type\n";
             E->dump(Out);
             Out << "\n";
@@ -2446,6 +2446,9 @@ class Verifier : public ASTWalker {
     }
 
     void verifyChecked(VarDecl *var) {
+      if (!var->hasInterfaceType())
+        return;
+
       PrettyStackTraceDecl debugStack("verifying VarDecl", var);
 
       // Variables must have materializable type.
@@ -2472,27 +2475,21 @@ class Verifier : public ASTWalker {
       }
 
       Type typeForAccessors = var->getValueInterfaceType();
-      if (!var->getDeclContext()->contextHasLazyGenericEnvironment()) {
-        typeForAccessors =
-            var->getDeclContext()->mapTypeIntoContext(typeForAccessors);
-        if (const FuncDecl *getter = var->getAccessor(AccessorKind::Get)) {
-          if (getter->getParameters()->size() != 0) {
-            Out << "property getter has parameters\n";
+      if (const FuncDecl *getter = var->getAccessor(AccessorKind::Get)) {
+        if (getter->getParameters()->size() != 0) {
+          Out << "property getter has parameters\n";
+          abort();
+        }
+        if (getter->hasInterfaceType()) {
+          Type getterResultType = getter->getResultInterfaceType();
+          if (!getterResultType->isEqual(typeForAccessors)) {
+            Out << "property and getter have mismatched types: '";
+            typeForAccessors.print(Out);
+            Out << "' vs. '";
+            getterResultType.print(Out);
+            Out << "'\n";
             abort();
           }
-          if (getter->hasInterfaceType()) {
-            Type getterResultType = getter->getResultInterfaceType();
-            getterResultType =
-                var->getDeclContext()->mapTypeIntoContext(getterResultType);
-            if (!getterResultType->isEqual(typeForAccessors)) {
-              Out << "property and getter have mismatched types: '";
-              typeForAccessors.print(Out);
-              Out << "' vs. '";
-              getterResultType.print(Out);
-              Out << "'\n";
-              abort();
-            }
-          }
         }
       }
 
@@ -2512,15 +2509,12 @@ class Verifier : public ASTWalker {
           }
           const ParamDecl *param = setter->getParameters()->get(0);
           Type paramType = param->getInterfaceType();
-          if (!var->getDeclContext()->contextHasLazyGenericEnvironment()) {
-            paramType = var->getDeclContext()->mapTypeIntoContext(paramType);
-            if (!paramType->isEqual(typeForAccessors)) {
-              Out << "property and setter param have mismatched types:\n";
-              typeForAccessors.dump(Out, 2);
-              Out << "vs.\n";
-              paramType.dump(Out, 2);
-              abort();
-            }
+          if (!paramType->isEqual(typeForAccessors)) {
+            Out << "property and setter param have mismatched types:\n";
+            typeForAccessors.dump(Out, 2);
+            Out << "vs.\n";
+            paramType.dump(Out, 2);
+            abort();
           }
         }
       }
diff --git a/lib/AST/AccessRequests.cpp b/lib/AST/AccessRequests.cpp
index 6789a6c7e9035..befc0fb2d888b 100644
--- a/lib/AST/AccessRequests.cpp
+++ b/lib/AST/AccessRequests.cpp
@@ -161,8 +161,7 @@ static bool isStoredWithPrivateSetter(VarDecl *VD) {
     return false;
 
   if (VD->isLet() ||
-      (VD->getAccessor(AccessorKind::Set) &&
-       !VD->getAccessor(AccessorKind::Set)->isImplicit()))
+      VD->getParsedAccessor(AccessorKind::Set))
     return false;
 
   return true;
diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index 6112119d38587..c53261df81500 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -1970,6 +1970,28 @@ AccessorDecl *AbstractStorageDecl::getSynthesizedAccessor(AccessorKind kind) con
     nullptr);
 }
 
+AccessorDecl *AbstractStorageDecl::getOpaqueAccessor(AccessorKind kind) const {
+  auto *accessor = getAccessor(kind);
+  if (accessor && !accessor->isImplicit())
+    return accessor;
+
+  if (!requiresOpaqueAccessors())
+    return nullptr;
+
+  if (!requiresOpaqueAccessor(kind))
+    return nullptr;
+
+  return getSynthesizedAccessor(kind);
+}
+
+AccessorDecl *AbstractStorageDecl::getParsedAccessor(AccessorKind kind) const {
+  auto *accessor = getAccessor(kind);
+  if (accessor && !accessor->isImplicit())
+    return accessor;
+
+  return nullptr;
+}
+
 void AbstractStorageDecl::visitExpectedOpaqueAccessors(
                         llvm::function_ref<void (AccessorKind)> visit) const {
   if (!requiresOpaqueAccessors())
@@ -1993,8 +2015,9 @@ void AbstractStorageDecl::visitExpectedOpaqueAccessors(
 void AbstractStorageDecl::visitOpaqueAccessors(
                         llvm::function_ref<void (AccessorDecl*)> visit) const {
   visitExpectedOpaqueAccessors([&](AccessorKind kind) {
-    auto accessor = getAccessor(kind);
-    assert(accessor && "didn't have expected opaque accessor");
+    auto accessor = getSynthesizedAccessor(kind);
+    assert(!accessor->hasForcedStaticDispatch() &&
+            "opaque accessor with forced static dispatch?");
     visit(accessor);
   });
 }
@@ -4029,7 +4052,7 @@ ClassDecl::findOverridingDecl(const AbstractFunctionDecl *Method) const {
     auto *Storage = Accessor->getStorage();
     if (auto *Derived = ::findOverridingDecl(this, Storage)) {
       auto *DerivedStorage = cast<AbstractStorageDecl>(Derived);
-      return DerivedStorage->getAccessor(Accessor->getAccessorKind());
+      return DerivedStorage->getOpaqueAccessor(Accessor->getAccessorKind());
     }
 
     return nullptr;
@@ -4651,9 +4674,9 @@ bool AbstractStorageDecl::hasPrivateAccessor() const {
 }
 
 bool AbstractStorageDecl::hasDidSetOrWillSetDynamicReplacement() const {
-  if (auto *func = getAccessor(AccessorKind::DidSet))
+  if (auto *func = getParsedAccessor(AccessorKind::DidSet))
     return func->getAttrs().hasAttribute<DynamicReplacementAttr>();
-  if (auto *func = getAccessor(AccessorKind::WillSet))
+  if (auto *func = getParsedAccessor(AccessorKind::WillSet))
     return func->getAttrs().hasAttribute<DynamicReplacementAttr>();
   return false;
 }
@@ -4855,7 +4878,7 @@ getNameFromObjcAttribute(const ObjCAttr *attr, DeclName preferredName) {
 ObjCSelector
 AbstractStorageDecl::getObjCGetterSelector(Identifier preferredName) const {
   // If the getter has an @objc attribute with a name, use that.
-  if (auto getter = getAccessor(AccessorKind::Get)) {
+  if (auto getter = getParsedAccessor(AccessorKind::Get)) {
       if (auto name = getNameFromObjcAttribute(getter->getAttrs().
           getAttribute<ObjCAttr>(), preferredName))
         return *name;
@@ -4885,7 +4908,7 @@ AbstractStorageDecl::getObjCGetterSelector(Identifier preferredName) const {
 ObjCSelector
 AbstractStorageDecl::getObjCSetterSelector(Identifier preferredName) const {
   // If the setter has an @objc attribute with a name, use that.
-  auto setter = getAccessor(AccessorKind::Set);
+  auto setter = getParsedAccessor(AccessorKind::Set);
   auto objcAttr = setter ? setter->getAttrs().getAttribute<ObjCAttr>()
                          : nullptr;
   if (auto name = getNameFromObjcAttribute(objcAttr, DeclName(preferredName))) {
diff --git a/lib/AST/SwiftNameTranslation.cpp b/lib/AST/SwiftNameTranslation.cpp
index 28b1cd0562bbd..2a1d648e73507 100644
--- a/lib/AST/SwiftNameTranslation.cpp
+++ b/lib/AST/SwiftNameTranslation.cpp
@@ -114,7 +114,7 @@ getObjCNameForSwiftDecl(const ValueDecl *VD, DeclName PreferredName){
       return {BaseName, ObjCSelector()};
     return {VAD->getObjCPropertyName(), ObjCSelector()};
   } else if (auto *SD = dyn_cast<SubscriptDecl>(VD)) {
-    return getObjCNameForSwiftDecl(SD->getAccessor(AccessorKind::Get),
+    return getObjCNameForSwiftDecl(SD->getParsedAccessor(AccessorKind::Get),
                                    PreferredName);
   } else if (auto *EL = dyn_cast<EnumElementDecl>(VD)) {
     SmallString<64> Buffer;
diff --git a/lib/AST/Type.cpp b/lib/AST/Type.cpp
index 14d48897d4f81..cfb76673bbde3 100644
--- a/lib/AST/Type.cpp
+++ b/lib/AST/Type.cpp
@@ -2556,7 +2556,7 @@ bool ReplaceOpaqueTypesWithUnderlyingTypes::shouldPerformSubstitution(
       return true;
     }
   } else if (auto *asd = dyn_cast<AbstractStorageDecl>(namingDecl)) {
-    auto *getter = asd->getAccessor(AccessorKind::Get);
+    auto *getter = asd->getOpaqueAccessor(AccessorKind::Get);
     if (getter &&
         getter->getResilienceExpansion() == ResilienceExpansion::Minimal) {
       return true;
diff --git a/lib/ClangImporter/ImportDecl.cpp b/lib/ClangImporter/ImportDecl.cpp
index fbbe5cb92d107..e9b64689a60d1 100644
--- a/lib/ClangImporter/ImportDecl.cpp
+++ b/lib/ClangImporter/ImportDecl.cpp
@@ -3628,13 +3628,13 @@ namespace {
       case ImportedAccessorKind::PropertyGetter: {
         auto property = getImplicitProperty(importedName, decl);
         if (!property) return nullptr;
-        return property->getAccessor(AccessorKind::Get);
+        return property->getParsedAccessor(AccessorKind::Get);
       }
 
       case ImportedAccessorKind::PropertySetter:
         auto property = getImplicitProperty(importedName, decl);
         if (!property) return nullptr;
-        return property->getAccessor(AccessorKind::Set);
+        return property->getParsedAccessor(AccessorKind::Set);
       }
 
       return importFunctionDecl(decl, importedName, correctSwiftName, None);
@@ -5010,8 +5010,8 @@ namespace {
       // Only record overrides of class members.
       if (overridden) {
         result->setOverriddenDecl(overridden);
-        getter->setOverriddenDecl(overridden->getAccessor(AccessorKind::Get));
-        if (auto parentSetter = overridden->getAccessor(AccessorKind::Set))
+        getter->setOverriddenDecl(overridden->getParsedAccessor(AccessorKind::Get));
+        if (auto parentSetter = overridden->getParsedAccessor(AccessorKind::Set))
           if (setter)
             setter->setOverriddenDecl(parentSetter);
       }
@@ -6516,10 +6516,10 @@ void SwiftDeclConverter::recordObjCOverride(SubscriptDecl *subscript) {
 
     // The index types match. This is an override, so mark it as such.
     subscript->setOverriddenDecl(parentSub);
-    auto getterThunk = subscript->getAccessor(AccessorKind::Get);
-    getterThunk->setOverriddenDecl(parentSub->getAccessor(AccessorKind::Get));
-    if (auto parentSetter = parentSub->getAccessor(AccessorKind::Set)) {
-      if (auto setterThunk = subscript->getAccessor(AccessorKind::Set))
+    auto getterThunk = subscript->getParsedAccessor(AccessorKind::Get);
+    getterThunk->setOverriddenDecl(parentSub->getParsedAccessor(AccessorKind::Get));
+    if (auto parentSetter = parentSub->getParsedAccessor(AccessorKind::Set)) {
+      if (auto setterThunk = subscript->getParsedAccessor(AccessorKind::Set))
         setterThunk->setOverriddenDecl(parentSetter);
     }
 
@@ -8397,10 +8397,8 @@ ClangImporter::Implementation::createConstant(Identifier name, DeclContext *dc,
   func->computeType();
   func->setAccess(getOverridableAccessLevel(dc));
   func->setValidationToChecked();
-  func->setImplicit();
   func->setIsObjC(false);
   func->setIsDynamic(false);
-  func->setIsTransparent(false);
 
   func->setBodySynthesizer(synthesizeConstantGetterBody,
                            ConstantGetterBodyContextData(valueExpr, convertKind)
diff --git a/lib/IDE/Formatting.cpp b/lib/IDE/Formatting.cpp
index aafdf2e623f0d..89a27d52979ec 100644
--- a/lib/IDE/Formatting.cpp
+++ b/lib/IDE/Formatting.cpp
@@ -268,9 +268,8 @@ class FormatContext {
         //   return 0; <- No indentation added because of the getter.
         // }
         if (auto VD = dyn_cast_or_null<VarDecl>(Cursor->getAsDecl())) {
-          if (auto Getter = VD->getAccessor(AccessorKind::Get)) {
-            if (!Getter->isImplicit() &&
-                Getter->getAccessorKeywordLoc().isInvalid()) {
+          if (auto Getter = VD->getParsedAccessor(AccessorKind::Get)) {
+            if (Getter->getAccessorKeywordLoc().isInvalid()) {
               LineAndColumn = ParentLineAndColumn;
               continue;
             }
diff --git a/lib/IRGen/GenClass.cpp b/lib/IRGen/GenClass.cpp
index e181b522a6c65..bd5bc50bdad7a 100644
--- a/lib/IRGen/GenClass.cpp
+++ b/lib/IRGen/GenClass.cpp
@@ -1793,7 +1793,7 @@ namespace {
         }
 
         // Don't emit descriptors for properties without accessors.
-        auto getter = var->getAccessor(AccessorKind::Get);
+        auto getter = var->getOpaqueAccessor(AccessorKind::Get);
         if (!getter)
           return;
 
@@ -1804,7 +1804,7 @@ namespace {
         auto &methods = getMethodList(var);
         methods.push_back(getter);
 
-        if (auto setter = var->getAccessor(AccessorKind::Set))
+        if (auto setter = var->getOpaqueAccessor(AccessorKind::Set))
           methods.push_back(setter);
       }
     }
@@ -2030,13 +2030,13 @@ namespace {
     void visitSubscriptDecl(SubscriptDecl *subscript) {
       if (!requiresObjCSubscriptDescriptor(IGM, subscript)) return;
 
-      auto getter = subscript->getAccessor(AccessorKind::Get);
+      auto getter = subscript->getOpaqueAccessor(AccessorKind::Get);
       if (!getter) return;
 
       auto &methods = getMethodList(subscript);
       methods.push_back(getter);
 
-      if (auto setter = subscript->getAccessor(AccessorKind::Set))
+      if (auto setter = subscript->getOpaqueAccessor(AccessorKind::Set))
         methods.push_back(setter);
     }
   };
diff --git a/lib/IRGen/GenObjC.cpp b/lib/IRGen/GenObjC.cpp
index 73fcca83d8d02..98ae4cfec3b95 100644
--- a/lib/IRGen/GenObjC.cpp
+++ b/lib/IRGen/GenObjC.cpp
@@ -923,7 +923,7 @@ static llvm::Constant *getObjCGetterPointer(IRGenModule &IGM,
   if (isa<ProtocolDecl>(property->getDeclContext()))
     return llvm::ConstantPointerNull::get(IGM.Int8PtrTy);
 
-  SILDeclRef getter = SILDeclRef(property->getAccessor(AccessorKind::Get),
+  SILDeclRef getter = SILDeclRef(property->getOpaqueAccessor(AccessorKind::Get),
                                  SILDeclRef::Kind::Func)
     .asForeign();
 
@@ -944,7 +944,7 @@ static llvm::Constant *getObjCSetterPointer(IRGenModule &IGM,
   assert(property->isSettable(property->getDeclContext()) &&
          "property is not settable?!");
   
-  SILDeclRef setter = SILDeclRef(property->getAccessor(AccessorKind::Set),
+  SILDeclRef setter = SILDeclRef(property->getOpaqueAccessor(AccessorKind::Set),
                                  SILDeclRef::Kind::Func)
     .asForeign();
   return findSwiftAsObjCThunk(IGM, setter, silFn);
@@ -1013,8 +1013,7 @@ static CanSILFunctionType getObjCMethodType(IRGenModule &IGM,
 static clang::CanQualType getObjCPropertyType(IRGenModule &IGM,
                                               VarDecl *property) {
   // Use the lowered return type of the foreign getter.
-  auto getter = property->getAccessor(AccessorKind::Get);
-  assert(getter);
+  auto getter = property->getOpaqueAccessor(AccessorKind::Get);
   CanSILFunctionType methodTy = getObjCMethodType(IGM, getter);
   return IGM.getClangType(
       methodTy->getFormalCSemanticResult().getASTType());
@@ -1173,7 +1172,7 @@ SILFunction *irgen::emitObjCGetterDescriptorParts(IRGenModule &IGM,
   Selector getterSel(subscript, Selector::ForGetter);
   selectorRef = IGM.getAddrOfObjCMethodName(getterSel.str());
   auto methodTy = getObjCMethodType(IGM,
-                                    subscript->getAccessor(AccessorKind::Get));
+                              subscript->getOpaqueAccessor(AccessorKind::Get));
   atEncoding = getObjCEncodingForMethodType(IGM, methodTy, /*extended*/false);
   SILFunction *silFn = nullptr;
   impl = getObjCGetterPointer(IGM, subscript, silFn);
@@ -1250,7 +1249,7 @@ SILFunction *irgen::emitObjCSetterDescriptorParts(IRGenModule &IGM,
   Selector setterSel(subscript, Selector::ForSetter);
   selectorRef = IGM.getAddrOfObjCMethodName(setterSel.str());
   auto methodTy = getObjCMethodType(IGM,
-                                    subscript->getAccessor(AccessorKind::Set));
+                              subscript->getOpaqueAccessor(AccessorKind::Set));
   atEncoding = getObjCEncodingForMethodType(IGM, methodTy, /*extended*/false);
   SILFunction *silFn = nullptr;
   impl = getObjCSetterPointer(IGM, subscript, silFn);
@@ -1401,7 +1400,7 @@ bool irgen::requiresObjCPropertyDescriptor(IRGenModule &IGM,
   // Don't generate a descriptor for a property without any accessors.
   // This is only possible in SIL files because Sema will normally
   // implicitly synthesize accessors for @objc properties.
-  return property->isObjC() && property->getAccessor(AccessorKind::Get);
+  return property->isObjC() && property->requiresOpaqueAccessors();
 }
 
 bool irgen::requiresObjCSubscriptDescriptor(IRGenModule &IGM,
diff --git a/lib/IRGen/Linking.cpp b/lib/IRGen/Linking.cpp
index 0a6e7864f9258..be2b9485b6729 100644
--- a/lib/IRGen/Linking.cpp
+++ b/lib/IRGen/Linking.cpp
@@ -567,7 +567,7 @@ SILLinkage LinkEntity::getLinkage(ForDefinition_t forDefinition) const {
     // property itself (for instance, with a private/internal property whose
     // accessor is @inlinable or @usableFromInline)
     auto getterDecl = cast<AbstractStorageDecl>(getDecl())
-      ->getAccessor(AccessorKind::Get);
+      ->getOpaqueAccessor(AccessorKind::Get);
     return getSILLinkage(getDeclLinkage(getterDecl), forDefinition);
   }
 
diff --git a/lib/Index/Index.cpp b/lib/Index/Index.cpp
index 49305a7177b71..cfc5e93e6f978 100644
--- a/lib/Index/Index.cpp
+++ b/lib/Index/Index.cpp
@@ -1062,14 +1062,10 @@ bool IndexSwiftASTWalker::report(ValueDecl *D) {
   if (startEntityDecl(D)) {
     // Pass accessors.
     if (auto StoreD = dyn_cast<AbstractStorageDecl>(D)) {
-      auto isNullOrImplicit = [](const Decl *D) -> bool {
-        return !D || D->isImplicit();
-      };
-
       bool usedPseudoAccessors = false;
       if (isa<VarDecl>(D) &&
-          isNullOrImplicit(StoreD->getAccessor(AccessorKind::Get)) &&
-          isNullOrImplicit(StoreD->getAccessor(AccessorKind::Set))) {
+          !StoreD->getParsedAccessor(AccessorKind::Get) &&
+          !StoreD->getParsedAccessor(AccessorKind::Set)) {
         usedPseudoAccessors = true;
         auto VarD = cast<VarDecl>(D);
         // No actual getter or setter, pass 'pseudo' accessors.
diff --git a/lib/ParseSIL/ParseSIL.cpp b/lib/ParseSIL/ParseSIL.cpp
index 6d4e651d28318..c9a8d791ad895 100644
--- a/lib/ParseSIL/ParseSIL.cpp
+++ b/lib/ParseSIL/ParseSIL.cpp
@@ -1447,7 +1447,7 @@ bool SILParser::parseSILDeclRef(SILDeclRef &Result,
         size_t destI = 0;
         for (size_t srcI = 0, e = values.size(); srcI != e; ++srcI) {
           if (auto storage = dyn_cast<AbstractStorageDecl>(values[srcI]))
-            if (auto accessor = storage->getAccessor(*accessorKind))
+            if (auto accessor = storage->getOpaqueAccessor(*accessorKind))
               values[destI++] = accessor;
         }
         values.resize(destI);
diff --git a/lib/PrintAsObjC/PrintAsObjC.cpp b/lib/PrintAsObjC/PrintAsObjC.cpp
index e46ecb0f19208..241737360afbe 100644
--- a/lib/PrintAsObjC/PrintAsObjC.cpp
+++ b/lib/PrintAsObjC/PrintAsObjC.cpp
@@ -1256,23 +1256,25 @@ class ObjCPrinter : private DeclVisitor<ObjCPrinter>,
 
     printAvailability(VD);
 
+    auto *getter = VD->getOpaqueAccessor(AccessorKind::Get);
+    auto *setter = VD->getOpaqueAccessor(AccessorKind::Set);
+
     os << ";";
     if (VD->isStatic()) {
       os << ")\n";
       // Older Clangs don't support class properties, so print the accessors as
       // well. This is harmless.
-      printAbstractFunctionAsMethod(VD->getAccessor(AccessorKind::Get), true);
+      printAbstractFunctionAsMethod(getter, true);
       if (isSettable) {
-        auto *setter = VD->getAccessor(AccessorKind::Set);
         assert(setter && "settable ObjC property missing setter decl");
         printAbstractFunctionAsMethod(setter, true);
       }
     } else {
       os << "\n";
       if (looksLikeInitMethod(VD->getObjCGetterSelector()))
-        printAbstractFunctionAsMethod(VD->getAccessor(AccessorKind::Get), false);
+        printAbstractFunctionAsMethod(getter, false);
       if (isSettable && looksLikeInitMethod(VD->getObjCSetterSelector()))
-        printAbstractFunctionAsMethod(VD->getAccessor(AccessorKind::Set), false);
+        printAbstractFunctionAsMethod(setter, false);
     }
   }
 
@@ -1287,9 +1289,10 @@ class ObjCPrinter : private DeclVisitor<ObjCPrinter>,
       isNSUIntegerSubscript = isNSUInteger(indexParam->getType());
     }
 
-    printAbstractFunctionAsMethod(SD->getAccessor(AccessorKind::Get), false,
+    auto *getter = SD->getOpaqueAccessor(AccessorKind::Get);
+    printAbstractFunctionAsMethod(getter, false,
                                   isNSUIntegerSubscript);
-    if (auto setter = SD->getAccessor(AccessorKind::Set))
+    if (auto *setter = SD->getOpaqueAccessor(AccessorKind::Set))
       printAbstractFunctionAsMethod(setter, false, isNSUIntegerSubscript);
   }
 
diff --git a/lib/SIL/SIL.cpp b/lib/SIL/SIL.cpp
index 7accc9f56fbb5..3d12371f912bf 100644
--- a/lib/SIL/SIL.cpp
+++ b/lib/SIL/SIL.cpp
@@ -213,9 +213,10 @@ bool AbstractStorageDecl::exportsPropertyDescriptor() const {
   if (isa<ProtocolDecl>(getDeclContext()))
     return false;
   
-  // Any property that's potentially resilient should have accessors
-  // synthesized.
-  if (!getAccessor(AccessorKind::Get))
+  // FIXME: We should support properties and subscripts with '_read' accessors;
+  // 'get' is not part of the opaque accessor set there.
+  auto *getter = getOpaqueAccessor(AccessorKind::Get);
+  if (!getter)
     return false;
 
   // If the getter is mutating, we cannot form a keypath to it at all.
@@ -231,8 +232,7 @@ bool AbstractStorageDecl::exportsPropertyDescriptor() const {
   // then we still do.
 
   // Check the linkage of the declaration.
-  auto getter = SILDeclRef(getAccessor(AccessorKind::Get));
-  auto getterLinkage = getter.getLinkage(ForDefinition);
+  auto getterLinkage = SILDeclRef(getter).getLinkage(ForDefinition);
   
   switch (getterLinkage) {
   case SILLinkage::Public:
diff --git a/lib/SIL/TypeLowering.cpp b/lib/SIL/TypeLowering.cpp
index a43a16fe97626..45c26a6ef7b50 100644
--- a/lib/SIL/TypeLowering.cpp
+++ b/lib/SIL/TypeLowering.cpp
@@ -2184,7 +2184,8 @@ TypeConverter::getLoweredLocalCaptures(AnyFunctionRef fn) {
       // of its accessors.
       if (auto capturedVar = dyn_cast<VarDecl>(capture.getDecl())) {
         auto collectAccessorCaptures = [&](AccessorKind kind) {
-          collectFunctionCaptures(capturedVar->getAccessor(kind));
+          if (auto *accessor = capturedVar->getParsedAccessor(kind))
+            collectFunctionCaptures(accessor);
         };
 
         if (!capture.isDirect()) {
@@ -2212,6 +2213,9 @@ TypeConverter::getLoweredLocalCaptures(AnyFunctionRef fn) {
           case WriteImplKind::Stored:
             break;
           case WriteImplKind::StoredWithObservers:
+            collectAccessorCaptures(AccessorKind::WillSet);
+            collectAccessorCaptures(AccessorKind::DidSet);
+            break;
           case WriteImplKind::Set:
             collectAccessorCaptures(AccessorKind::Set);
             break;
diff --git a/lib/SILGen/SILGen.cpp b/lib/SILGen/SILGen.cpp
index 24fbc52a37a47..93f5b0be803b4 100644
--- a/lib/SILGen/SILGen.cpp
+++ b/lib/SILGen/SILGen.cpp
@@ -1240,7 +1240,7 @@ void SILGenModule::emitObjCMethodThunk(FuncDecl *method) {
 }
 
 void SILGenModule::emitObjCPropertyMethodThunks(AbstractStorageDecl *prop) {
-  auto *getter = prop->getAccessor(AccessorKind::Get);
+  auto *getter = prop->getOpaqueAccessor(AccessorKind::Get);
 
   // If we don't actually need an entry point for the getter, do nothing.
   if (!getter || !requiresObjCMethodEntryPoint(getter))
@@ -1270,7 +1270,7 @@ void SILGenModule::emitObjCPropertyMethodThunks(AbstractStorageDecl *prop) {
     return;
 
   // FIXME: Add proper location.
-  auto *setter = prop->getAccessor(AccessorKind::Set);
+  auto *setter = prop->getOpaqueAccessor(AccessorKind::Set);
   auto setterRef = SILDeclRef(setter, SILDeclRef::Kind::Func).asForeign();
 
   SILFunction *f = getFunction(setterRef, ForDefinition);
@@ -1396,11 +1396,12 @@ static bool canStorageUseTrivialDescriptor(SILGenModule &SGM,
       // property in a fixed-layout type.
       return !decl->isFormallyResilient();
     }
+
     // If the type is computed and doesn't have a setter that's hidden from
     // the public, then external components can form the canonical key path
     // without our help.
-    auto setter = decl->getAccessor(AccessorKind::Set);
-    if (setter == nullptr)
+    auto *setter = decl->getOpaqueAccessor(AccessorKind::Set);
+    if (!setter)
       return true;
 
     if (setter->getFormalAccessScope(nullptr, true).isPublic())
@@ -1415,8 +1416,8 @@ static bool canStorageUseTrivialDescriptor(SILGenModule &SGM,
   // or a fixed-layout type may not have been.
   // Without availability information, only get-only computed properties
   // can resiliently use trivial descriptors.
-  return !SGM.canStorageUseStoredKeyPathComponent(decl, expansion)
-    && decl->getAccessor(AccessorKind::Set) == nullptr;
+  return (!SGM.canStorageUseStoredKeyPathComponent(decl, expansion) &&
+          !decl->supportsMutation());
 }
 
 void SILGenModule::tryEmitPropertyDescriptor(AbstractStorageDecl *decl) {
diff --git a/lib/SILGen/SILGenApply.cpp b/lib/SILGen/SILGenApply.cpp
index 495dae4aa9001..9adf84323a721 100644
--- a/lib/SILGen/SILGenApply.cpp
+++ b/lib/SILGen/SILGenApply.cpp
@@ -5811,7 +5811,7 @@ RValue SILGenFunction::emitDynamicMemberRefExpr(DynamicMemberRefExpr *e,
   // Create the branch.
   FuncDecl *memberFunc;
   if (auto *VD = dyn_cast<VarDecl>(e->getMember().getDecl())) {
-    memberFunc = VD->getAccessor(AccessorKind::Get);
+    memberFunc = VD->getOpaqueAccessor(AccessorKind::Get);
     memberMethodTy = FunctionType::get({}, memberMethodTy);
   } else
     memberFunc = cast<FuncDecl>(e->getMember().getDecl());
@@ -5920,7 +5920,7 @@ RValue SILGenFunction::emitDynamicSubscriptExpr(DynamicSubscriptExpr *e,
 
   // Create the branch.
   auto subscriptDecl = cast<SubscriptDecl>(e->getMember().getDecl());
-  auto member = SILDeclRef(subscriptDecl->getAccessor(AccessorKind::Get),
+  auto member = SILDeclRef(subscriptDecl->getOpaqueAccessor(AccessorKind::Get),
                            SILDeclRef::Kind::Func)
     .asForeign();
   B.createDynamicMethodBranch(e, base, member, hasMemberBB, noMemberBB);
diff --git a/lib/SILGen/SILGenExpr.cpp b/lib/SILGen/SILGenExpr.cpp
index 5c7f47c83b7ea..c143cd28eb1b7 100644
--- a/lib/SILGen/SILGenExpr.cpp
+++ b/lib/SILGen/SILGenExpr.cpp
@@ -2604,9 +2604,9 @@ loadIndexValuesForKeyPathComponent(SILGenFunction &SGF, SILLocation loc,
 static AccessorDecl *
 getRepresentativeAccessorForKeyPath(AbstractStorageDecl *storage) {
   if (storage->requiresOpaqueGetter())
-    return storage->getAccessor(AccessorKind::Get);
+    return storage->getOpaqueAccessor(AccessorKind::Get);
   assert(storage->requiresOpaqueReadCoroutine());
-  return storage->getAccessor(AccessorKind::Read);
+  return storage->getOpaqueAccessor(AccessorKind::Read);
 }
 
 static SILFunction *getOrCreateKeyPathGetter(SILGenModule &SGM,
@@ -2755,7 +2755,7 @@ static SILFunction *getOrCreateKeyPathSetter(SILGenModule &SGM,
   // back to the declaration whose setter introduced the witness table
   // entry.
   if (isa<ProtocolDecl>(property->getDeclContext())) {
-    auto setter = property->getAccessor(AccessorKind::Set);
+    auto setter = property->getOpaqueAccessor(AccessorKind::Set);
     if (!SILDeclRef::requiresNewWitnessTableEntry(setter)) {
       // Find the setter that does have a witness table entry.
       auto wtableSetter =
diff --git a/lib/SILGen/SILGenLValue.cpp b/lib/SILGen/SILGenLValue.cpp
index afac9b7250c65..22ed222d99c57 100644
--- a/lib/SILGen/SILGenLValue.cpp
+++ b/lib/SILGen/SILGenLValue.cpp
@@ -1307,11 +1307,10 @@ namespace {
           // If we have a nonmutating setter on a value type, the call
           // captures all of 'self' and we cannot rewrite an assignment
           // into an initialization.
-          auto setter = VD->getAccessor(AccessorKind::Set);
-          if (setter->isNonMutating() &&
-              setter->getDeclContext()->getSelfNominalTypeDecl() &&
-              setter->isInstanceMember() &&
-              !setter->getDeclContext()->getDeclaredInterfaceType()
+          if (!VD->isSetterMutating() &&
+              VD->getDeclContext()->getSelfNominalTypeDecl() &&
+              VD->isInstanceMember() &&
+              !VD->getDeclContext()->getDeclaredInterfaceType()
                   ->hasReferenceSemantics()) {
             return false;
           }
@@ -2485,7 +2484,7 @@ namespace {
 
     void emitUsingAccessor(AccessorKind accessorKind, bool isDirect) {
       auto accessor =
-        SGF.SGM.getAccessorDeclRef(Storage->getAccessor(accessorKind));
+        SGF.SGM.getAccessorDeclRef(Storage->getOpaqueAccessor(accessorKind));
 
       switch (accessorKind) {
       case AccessorKind::Get:
@@ -2915,7 +2914,7 @@ static SGFAccessKind getBaseAccessKind(SILGenModule &SGM,
 
   case AccessStrategy::DirectToAccessor:
   case AccessStrategy::DispatchToAccessor: {
-    auto accessor = member->getAccessor(strategy.getAccessor());
+    auto accessor = member->getOpaqueAccessor(strategy.getAccessor());
     return getBaseAccessKindForAccessor(SGM, accessor, baseFormalType);
   }
     
@@ -2968,10 +2967,10 @@ LValue SILGenLValue::visitMemberRefExpr(MemberRefExpr *e,
   // dynamic replacement directly call the implementation.
   if (isContextRead && isOnSelfParameter && strategy.hasAccessor() &&
       strategy.getAccessor() == AccessorKind::Get &&
-      var->getAccessor(AccessorKind::Read)) {
+      var->getOpaqueAccessor(AccessorKind::Read)) {
     bool isObjC = false;
     auto readAccessor =
-        SGF.SGM.getAccessorDeclRef(var->getAccessor(AccessorKind::Read));
+        SGF.SGM.getAccessorDeclRef(var->getOpaqueAccessor(AccessorKind::Read));
     if (isCallToReplacedInDynamicReplacement(
             SGF, readAccessor.getAbstractFunctionDecl(), isObjC)) {
       accessSemantics = AccessSemantics::DirectToImplementation;
@@ -3139,10 +3138,10 @@ LValue SILGenLValue::visitSubscriptExpr(SubscriptExpr *e,
   // dynamic replacement directly call the implementation.
   if (isContextRead && isOnSelfParameter && strategy.hasAccessor() &&
       strategy.getAccessor() == AccessorKind::Get &&
-      decl->getAccessor(AccessorKind::Read)) {
+      decl->getOpaqueAccessor(AccessorKind::Read)) {
     bool isObjC = false;
     auto readAccessor =
-        SGF.SGM.getAccessorDeclRef(decl->getAccessor(AccessorKind::Read));
+        SGF.SGM.getAccessorDeclRef(decl->getOpaqueAccessor(AccessorKind::Read));
     if (isCallToReplacedInDynamicReplacement(
             SGF, readAccessor.getAbstractFunctionDecl(), isObjC)) {
       accessSemantics = AccessSemantics::DirectToImplementation;
diff --git a/lib/SILGen/SILGenType.cpp b/lib/SILGen/SILGenType.cpp
index c5d4fda7e7903..045d65b6f2c37 100644
--- a/lib/SILGen/SILGenType.cpp
+++ b/lib/SILGen/SILGenType.cpp
@@ -358,11 +358,12 @@ template<typename T> class SILGenWitnessTable : public SILWitnessVisitor<T> {
       return asDerived().addMissingMethod(requirementRef);
 
     auto witnessStorage = cast<AbstractStorageDecl>(witness.getDecl());
-    auto witnessAccessor =
-      witnessStorage->getAccessor(reqAccessor->getAccessorKind());
-    if (!witnessAccessor)
+    if (reqAccessor->isSetter() && !witnessStorage->supportsMutation())
       return asDerived().addMissingMethod(requirementRef);
 
+    auto witnessAccessor =
+      witnessStorage->getSynthesizedAccessor(reqAccessor->getAccessorKind());
+
     return addMethodImplementation(requirementRef,
                                    SILDeclRef(witnessAccessor,
                                               SILDeclRef::Kind::Func),
@@ -1120,8 +1121,8 @@ class SILGenExtension : public TypeMemberVisitor<SILGenExtension> {
 
       if (hasDidSetOrWillSetDynamicReplacement &&
           isa<ExtensionDecl>(storage->getDeclContext()) &&
-          fd != storage->getAccessor(AccessorKind::WillSet) &&
-          fd != storage->getAccessor(AccessorKind::DidSet))
+          fd != storage->getParsedAccessor(AccessorKind::WillSet) &&
+          fd != storage->getParsedAccessor(AccessorKind::DidSet))
         return;
     }
     SGM.emitFunction(fd);
diff --git a/lib/Sema/CSApply.cpp b/lib/Sema/CSApply.cpp
index 8db5218d4bad4..a16ccdf9d861e 100644
--- a/lib/Sema/CSApply.cpp
+++ b/lib/Sema/CSApply.cpp
@@ -4085,12 +4085,12 @@ namespace {
           // The property is non-settable, so add "getter:".
           primaryDiag.fixItInsert(modifierLoc, "getter: ");
           E->overrideObjCSelectorKind(ObjCSelectorExpr::Getter, modifierLoc);
-          method = var->getAccessor(AccessorKind::Get);
+          method = var->getOpaqueAccessor(AccessorKind::Get);
           break;
         }
 
         case ObjCSelectorExpr::Getter:
-          method = var->getAccessor(AccessorKind::Get);
+          method = var->getOpaqueAccessor(AccessorKind::Get);
           break;
 
         case ObjCSelectorExpr::Setter:
@@ -4111,7 +4111,7 @@ namespace {
             return E;
           }
 
-          method = var->getAccessor(AccessorKind::Set);
+          method = var->getOpaqueAccessor(AccessorKind::Set);
           break;
         }
       } else {
diff --git a/lib/Sema/CodeSynthesis.cpp b/lib/Sema/CodeSynthesis.cpp
index 24235a9349fbd..a90bdcd0bafbf 100644
--- a/lib/Sema/CodeSynthesis.cpp
+++ b/lib/Sema/CodeSynthesis.cpp
@@ -165,8 +165,6 @@ static void finishImplicitAccessor(AccessorDecl *accessor,
 
 static AccessorDecl *createGetterPrototype(AbstractStorageDecl *storage,
                                            ASTContext &ctx) {
-  assert(!storage->getAccessor(AccessorKind::Get));
-
   SourceLoc loc = storage->getLoc();
 
   GenericEnvironment *genericEnvironmentOfLazyAccessor = nullptr;
@@ -244,7 +242,6 @@ static AccessorDecl *createGetterPrototype(AbstractStorageDecl *storage,
 static AccessorDecl *createSetterPrototype(AbstractStorageDecl *storage,
                                            ASTContext &ctx,
                                            AccessorDecl *getter = nullptr) {
-  assert(!storage->getAccessor(AccessorKind::Set));
   assert(storage->supportsMutation());
 
   SourceLoc loc = storage->getLoc();
@@ -370,8 +367,8 @@ IsAccessorTransparentRequest::evaluate(Evaluator &evaluator,
       // FIXME: This should be folded into the WriteImplKind below.
       if (auto var = dyn_cast<VarDecl>(storage)) {
         if (var->hasAttachedPropertyWrapper()) {
-          if (var->getAccessor(AccessorKind::DidSet) ||
-              var->getAccessor(AccessorKind::WillSet))
+          if (var->getParsedAccessor(AccessorKind::DidSet) ||
+              var->getParsedAccessor(AccessorKind::WillSet))
             return false;
 
           break;
@@ -463,11 +460,11 @@ createCoroutineAccessorPrototype(AbstractStorageDecl *storage,
   // the storage (and its getters/setters if it has them).
   SmallVector<const Decl *, 2> asAvailableAs;
   asAvailableAs.push_back(storage);
-  if (FuncDecl *getter = storage->getAccessor(AccessorKind::Get)) {
+  if (FuncDecl *getter = storage->getParsedAccessor(AccessorKind::Get)) {
     asAvailableAs.push_back(getter);
   }
   if (kind == AccessorKind::Modify) {
-    if (FuncDecl *setter = storage->getAccessor(AccessorKind::Set)) {
+    if (FuncDecl *setter = storage->getParsedAccessor(AccessorKind::Set)) {
       asAvailableAs.push_back(setter);
     }
   }
@@ -1148,7 +1145,7 @@ synthesizeInheritedGetterBody(AccessorDecl *getter, ASTContext &ctx) {
 /// Synthesize the body of a getter which just delegates to an addressor.
 static std::pair<BraceStmt *, bool>
 synthesizeAddressedGetterBody(AccessorDecl *getter, ASTContext &ctx) {
-  assert(getter->getStorage()->getAccessor(AccessorKind::Address));
+  assert(getter->getStorage()->getParsedAccessor(AccessorKind::Address));
 
   // This should call the addressor.
   return synthesizeTrivialGetterBody(getter, TargetImpl::Implementation, ctx);
@@ -1158,7 +1155,7 @@ synthesizeAddressedGetterBody(AccessorDecl *getter, ASTContext &ctx) {
 /// coroutine accessor.
 static std::pair<BraceStmt *, bool>
 synthesizeReadCoroutineGetterBody(AccessorDecl *getter, ASTContext &ctx) {
-  assert(getter->getStorage()->getAccessor(AccessorKind::Read));
+  assert(getter->getStorage()->getParsedAccessor(AccessorKind::Read));
 
   // This should call the read coroutine.
   return synthesizeTrivialGetterBody(getter, TargetImpl::Implementation, ctx);
@@ -1323,22 +1320,6 @@ synthesizeModifyCoroutineSetterBody(AccessorDecl *setter, ASTContext &ctx) {
                                                 setter->getStorage(), ctx);
 }
 
-/// The specified AbstractStorageDecl was just found to satisfy a
-/// protocol property requirement.  Ensure that it has the full
-/// complement of accessors.
-void TypeChecker::synthesizeWitnessAccessorsForStorage(
-                                             AbstractStorageDecl *requirement,
-                                             AbstractStorageDecl *storage) {
-  // Make sure the protocol requirement itself has the right accessors.
-  // FIXME: This should be a request kicked off by SILGen.
-  DeclsToFinalize.insert(requirement);
-
-  requirement->visitExpectedOpaqueAccessors([&](AccessorKind kind) {
-    // Force synthesis if necessary.
-    (void) storage->getSynthesizedAccessor(kind);
-  });
-}
-
 /// Given a VarDecl with a willSet: and/or didSet: specifier, synthesize the
 /// setter which calls them.
 static std::pair<BraceStmt *, bool>
@@ -1399,7 +1380,7 @@ synthesizeObservedSetterBody(AccessorDecl *Set, TargetImpl target,
   // TODO: check the body of didSet to only do this load (which may call the
   // superclass getter) if didSet takes an argument.
   VarDecl *OldValue = nullptr;
-  if (VD->getAccessor(AccessorKind::DidSet)) {
+  if (VD->getParsedAccessor(AccessorKind::DidSet)) {
     Expr *OldValueExpr
       = buildStorageReference(Set, VD, target, /*isLValue=*/true, Ctx);
     OldValueExpr = new (Ctx) LoadExpr(OldValueExpr, VD->getType());
@@ -1416,7 +1397,7 @@ synthesizeObservedSetterBody(AccessorDecl *Set, TargetImpl target,
     SetterBody.push_back(OldValue);
   }
 
-  if (auto willSet = VD->getAccessor(AccessorKind::WillSet))
+  if (auto willSet = VD->getParsedAccessor(AccessorKind::WillSet))
     callObserver(willSet, ValueDecl);
   
   // Create an assignment into the storage or call to superclass setter.
@@ -1425,7 +1406,7 @@ synthesizeObservedSetterBody(AccessorDecl *Set, TargetImpl target,
   createPropertyStoreOrCallSuperclassSetter(Set, ValueDRE, VD, target,
                                             SetterBody, Ctx);
 
-  if (auto didSet = VD->getAccessor(AccessorKind::DidSet))
+  if (auto didSet = VD->getParsedAccessor(AccessorKind::DidSet))
     callObserver(didSet, OldValue);
 
   return { BraceStmt::create(Ctx, Loc, SetterBody, Loc, true),
@@ -1792,11 +1773,9 @@ PropertyWrapperMutabilityRequest::evaluate(Evaluator &,
   unsigned numWrappers = var->getAttachedPropertyWrappers().size();
   if (numWrappers < 1)
     return None;
-  if (var->getAccessor(AccessorKind::Get) &&
-      !var->getAccessor(AccessorKind::Get)->isImplicit())
+  if (var->getParsedAccessor(AccessorKind::Get))
     return None;
-  if (var->getAccessor(AccessorKind::Set) &&
-      !var->getAccessor(AccessorKind::Set)->isImplicit())
+  if (var->getParsedAccessor(AccessorKind::Set))
     return None;
 
   // Start with the traits from the outermost wrapper.
@@ -2076,7 +2055,7 @@ static void finishPropertyWrapperImplInfo(VarDecl *var,
   }
 
   bool wrapperSetterIsUsable = false;
-  if (var->getAccessor(AccessorKind::Set)) {
+  if (var->getParsedAccessor(AccessorKind::Set)) {
     wrapperSetterIsUsable = true;
   } else if (parentSF && parentSF->Kind != SourceFileKind::Interface
              && !var->isLet()) {
@@ -2153,11 +2132,6 @@ static void finishStorageImplInfo(AbstractStorageDecl *storage,
     finishProtocolStorageImplInfo(storage, info);
 }
 
-static bool hasParsedAccessor(AbstractStorageDecl *storage, AccessorKind kind) {
-  auto *accessor = storage->getAccessor(kind);
-  return (accessor && !accessor->isImplicit());
-}
-
 /// Gets the storage info of the provided storage decl if it has the
 /// @_hasStorage attribute and it's not in SIL mode.
 ///
@@ -2179,8 +2153,8 @@ static StorageImplInfo classifyWithHasStorageAttr(VarDecl *var) {
   WriteImplKind writeImpl;
   ReadWriteImplKind readWriteImpl;
 
-  if (hasParsedAccessor(var, AccessorKind::Get) &&
-      hasParsedAccessor(var, AccessorKind::Set)) {
+  if (var->getParsedAccessor(AccessorKind::Get) &&
+      var->getParsedAccessor(AccessorKind::Set)) {
     // If we see `@_hasStorage var x: T { get set }`, then our property has
     // willSet/didSet observers.
     writeImpl = var->getAttrs().hasAttribute<OverrideAttr>() ?
@@ -2222,25 +2196,27 @@ StorageImplInfoRequest::evaluate(Evaluator &evaluator,
       auto *SF = storage->getDeclContext()->getParentSourceFile();
       if (SF && SF->Kind == SourceFileKind::SIL)
         return StorageImplInfo::getSimpleStored(
-          StorageIsMutable_t(hasParsedAccessor(var, AccessorKind::Set)));
+          var->getParsedAccessor(AccessorKind::Set)
+          ? StorageIsMutable
+          : StorageIsNotMutable);
 
       return classifyWithHasStorageAttr(var);
     }
   }
 
-  bool hasWillSet = hasParsedAccessor(storage, AccessorKind::WillSet);
-  bool hasDidSet = hasParsedAccessor(storage, AccessorKind::DidSet);
-  bool hasSetter = hasParsedAccessor(storage, AccessorKind::Set);
-  bool hasModify = hasParsedAccessor(storage, AccessorKind::Modify);
-  bool hasMutableAddress = hasParsedAccessor(storage, AccessorKind::MutableAddress);
+  bool hasWillSet = storage->getParsedAccessor(AccessorKind::WillSet);
+  bool hasDidSet = storage->getParsedAccessor(AccessorKind::DidSet);
+  bool hasSetter = storage->getParsedAccessor(AccessorKind::Set);
+  bool hasModify = storage->getParsedAccessor(AccessorKind::Modify);
+  bool hasMutableAddress = storage->getParsedAccessor(AccessorKind::MutableAddress);
 
   // 'get', 'read', and a non-mutable addressor are all exclusive.
   ReadImplKind readImpl;
-  if (hasParsedAccessor(storage, AccessorKind::Get)) {
+  if (storage->getParsedAccessor(AccessorKind::Get)) {
     readImpl = ReadImplKind::Get;
-  } else if (hasParsedAccessor(storage, AccessorKind::Read)) {
+  } else if (storage->getParsedAccessor(AccessorKind::Read)) {
     readImpl = ReadImplKind::Read;
-  } else if (hasParsedAccessor(storage, AccessorKind::Address)) {
+  } else if (storage->getParsedAccessor(AccessorKind::Address)) {
     readImpl = ReadImplKind::Address;
 
   // If there's a writing accessor of any sort, there must also be a
@@ -2349,7 +2325,7 @@ RequiresOpaqueAccessorsRequest::evaluate(Evaluator &evaluator,
   // But we might need to create opaque accessors for them.
   if (auto sourceFile = dc->getParentSourceFile()) {
     if (sourceFile->Kind == SourceFileKind::SIL) {
-      if (!var->getAccessor(AccessorKind::Get))
+      if (!var->getParsedAccessor(AccessorKind::Get))
         return false;
     }
   }
@@ -2451,8 +2427,8 @@ synthesizeSetterBody(AccessorDecl *setter, ASTContext &ctx) {
     }
 
     if (var->hasAttachedPropertyWrapper()) {
-      if (var->getAccessor(AccessorKind::WillSet) ||
-          var->getAccessor(AccessorKind::DidSet)) {
+      if (var->getParsedAccessor(AccessorKind::WillSet) ||
+          var->getParsedAccessor(AccessorKind::DidSet)) {
         return synthesizeObservedSetterBody(setter, TargetImpl::Wrapper, ctx);
       }
 
diff --git a/lib/Sema/TypeCheckAttr.cpp b/lib/Sema/TypeCheckAttr.cpp
index 2d4e7f6d2dbf5..aae1d1665b513 100644
--- a/lib/Sema/TypeCheckAttr.cpp
+++ b/lib/Sema/TypeCheckAttr.cpp
@@ -2499,8 +2499,8 @@ void AttributeChecker::visitCustomAttr(CustomAttr *attr) {
       decl = func;
     } else if (auto storage = dyn_cast<AbstractStorageDecl>(D)) {
       decl = storage;
-      auto getter = storage->getAccessor(AccessorKind::Get);
-      if (!getter || getter->isImplicit() || !getter->hasBody()) {
+      auto getter = storage->getParsedAccessor(AccessorKind::Get);
+      if (!getter || !getter->hasBody()) {
         TC.diagnose(attr->getLocation(),
                     diag::function_builder_attribute_on_storage_without_getter,
                     nominal->getFullName(),
@@ -2836,8 +2836,8 @@ void TypeChecker::addImplicitDynamicAttribute(Decl *D) {
     // exclusivity checking.
     // If there is a didSet or willSet function we allow dynamic replacement.
     if (VD->hasStorage() &&
-        !VD->getAccessor(AccessorKind::DidSet) &&
-        !VD->getAccessor(AccessorKind::WillSet))
+        !VD->getParsedAccessor(AccessorKind::DidSet) &&
+        !VD->getParsedAccessor(AccessorKind::WillSet))
       return;
     // Don't add dynamic to local variables.
     if (VD->getDeclContext()->isLocalContext())
diff --git a/lib/Sema/TypeCheckAvailability.cpp b/lib/Sema/TypeCheckAvailability.cpp
index 6f90ac8cc62ea..82fce21a28820 100644
--- a/lib/Sema/TypeCheckAvailability.cpp
+++ b/lib/Sema/TypeCheckAvailability.cpp
@@ -2519,31 +2519,31 @@ class AvailabilityWalker : public ASTWalker {
     if (!D)
       return;
 
-    if (!D->hasAnyAccessors()) {
+    if (!D->requiresOpaqueAccessors()) {
       return;
     }
-    
+
     // Check availability of accessor functions.
     // TODO: if we're talking about an inlineable storage declaration,
     // this probably needs to be refined to not assume that the accesses are
     // specifically using the getter/setter.
     switch (AccessContext) {
     case MemberAccessContext::Getter:
-      diagAccessorAvailability(D->getAccessor(AccessorKind::Get),
+      diagAccessorAvailability(D->getOpaqueAccessor(AccessorKind::Get),
                                ReferenceRange, ReferenceDC, None);
       break;
 
     case MemberAccessContext::Setter:
-      diagAccessorAvailability(D->getAccessor(AccessorKind::Set),
+      diagAccessorAvailability(D->getOpaqueAccessor(AccessorKind::Set),
                                ReferenceRange, ReferenceDC, None);
       break;
 
     case MemberAccessContext::InOut:
-      diagAccessorAvailability(D->getAccessor(AccessorKind::Get),
+      diagAccessorAvailability(D->getOpaqueAccessor(AccessorKind::Get),
                                ReferenceRange, ReferenceDC,
                                DeclAvailabilityFlag::ForInout);
 
-      diagAccessorAvailability(D->getAccessor(AccessorKind::Set),
+      diagAccessorAvailability(D->getOpaqueAccessor(AccessorKind::Set),
                                ReferenceRange, ReferenceDC,
                                DeclAvailabilityFlag::ForInout);
       break;
diff --git a/lib/Sema/TypeCheckDecl.cpp b/lib/Sema/TypeCheckDecl.cpp
index bad450e06ae35..388e32abe1b82 100644
--- a/lib/Sema/TypeCheckDecl.cpp
+++ b/lib/Sema/TypeCheckDecl.cpp
@@ -2277,10 +2277,10 @@ IsGetterMutatingRequest::evaluate(Evaluator &evaluator,
   }
 
   auto checkMutability = [&](AccessorKind kind) -> bool {
-    auto *accessor = storage->getAccessor(kind);
+    auto *accessor = storage->getParsedAccessor(kind);
     if (!accessor)
       return false;
-    
+
     return accessor->isMutating();
   };
 
@@ -2337,7 +2337,7 @@ IsSetterMutatingRequest::evaluate(Evaluator &evaluator,
   case WriteImplKind::StoredWithObservers:
   case WriteImplKind::InheritedWithObservers:
   case WriteImplKind::Set: {
-    auto *setter = storage->getAccessor(AccessorKind::Set);
+    auto *setter = storage->getParsedAccessor(AccessorKind::Set);
 
     if (setter)
       result = setter->isMutating();
@@ -2347,7 +2347,7 @@ IsSetterMutatingRequest::evaluate(Evaluator &evaluator,
     // coroutine, check that it has the same mutatingness as the setter.
     // TODO: arguably this should require the spelling to match even when
     // it's the implied value.
-    auto modifyAccessor = storage->getAccessor(AccessorKind::Modify);
+    auto modifyAccessor = storage->getParsedAccessor(AccessorKind::Modify);
 
     if (impl.getReadWriteImpl() == ReadWriteImplKind::Modify &&
         modifyAccessor != nullptr) {
@@ -2369,11 +2369,11 @@ IsSetterMutatingRequest::evaluate(Evaluator &evaluator,
   }
 
   case WriteImplKind::MutableAddress:
-    return storage->getAccessor(AccessorKind::MutableAddress)
+    return storage->getParsedAccessor(AccessorKind::MutableAddress)
       ->isMutating();
 
   case WriteImplKind::Modify:
-    return storage->getAccessor(AccessorKind::Modify)
+    return storage->getParsedAccessor(AccessorKind::Modify)
       ->isMutating();
   }
   llvm_unreachable("bad storage kind");
@@ -2472,11 +2472,6 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
       (void) VD->isObjC();
       (void) VD->isDynamic();
 
-      // Make sure we finalize this declaration.
-      if (isa<ClassDecl>(VD) || isa<ProtocolDecl>(VD) ||
-          isa<AbstractStorageDecl>(VD))
-        TC.DeclsToFinalize.insert(VD);
-
       // If this is a member of a nominal type, don't allow it to have a name of
       // "Type" or "Protocol" since we reserve the X.Type and X.Protocol
       // expressions to mean something builtin to the language.  We *do* allow
@@ -2635,11 +2630,9 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
 
     // FIXME: Temporary hack until capture computation has been request-ified.
     if (VD->getDeclContext()->isLocalContext()) {
-      VD->visitExpectedOpaqueAccessors([&](AccessorKind kind) {
-        auto accessor = VD->getAccessor(kind);
-        if (!accessor) return;
-
-        TC.definedFunctions.push_back(accessor);
+      VD->visitOpaqueAccessors([&](AccessorDecl *accessor) {
+        if (accessor->isImplicit())
+          TC.definedFunctions.push_back(accessor);
       });
     }
 
@@ -3157,6 +3150,8 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
 
 
   void visitClassDecl(ClassDecl *CD) {
+    TC.DeclsToFinalize.insert(CD);
+
     TC.checkDeclAttributesEarly(CD);
 
     checkUnsupportedNestedType(CD);
@@ -3501,7 +3496,7 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     if (auto nominal = ED->getExtendedNominal()) {
       TC.validateDecl(nominal);
       if (auto *classDecl = dyn_cast<ClassDecl>(nominal))
-        TC.requestNominalLayout(classDecl);
+        TC.requestClassLayout(classDecl);
 
       // Check the raw values of an enum, since we might synthesize
       // RawRepresentable while checking conformances on this extension.
@@ -4145,14 +4140,6 @@ void TypeChecker::validateDecl(ValueDecl *D) {
 
     validateAttributes(*this, D);
 
-    // FIXME: IRGen likes to emit @objc protocol descriptors even if the
-    // protocol comes from a different module or translation unit.
-    //
-    // It would be nice if it didn't have to do that, then we could remove
-    // this case.
-    if (proto->isObjC())
-      requestNominalLayout(proto);
-
     break;
   }
 
@@ -4524,14 +4511,6 @@ void TypeChecker::validateDeclForNameLookup(ValueDecl *D) {
       return;
     proto->computeType();
 
-    // FIXME: IRGen likes to emit @objc protocol descriptors even if the
-    // protocol comes from a different module or translation unit.
-    //
-    // It would be nice if it didn't have to do that, then we could remove
-    // this case.
-    if (proto->isObjC())
-      requestNominalLayout(proto);
-
     break;
   }
   case DeclKind::AssociatedType: {
@@ -4596,96 +4575,59 @@ void TypeChecker::validateDeclForNameLookup(ValueDecl *D) {
 void TypeChecker::requestMemberLayout(ValueDecl *member) {
   auto *dc = member->getDeclContext();
   if (auto *classDecl = dyn_cast<ClassDecl>(dc))
-    requestNominalLayout(classDecl);
-  if (auto *protocolDecl = dyn_cast<ProtocolDecl>(dc))
-    requestNominalLayout(protocolDecl);
-
-  // If this represents (abstract) storage, form the appropriate accessors.
-  if (auto storage = dyn_cast<AbstractStorageDecl>(member))
-    DeclsToFinalize.insert(storage);
+    requestClassLayout(classDecl);
 }
 
-void TypeChecker::requestNominalLayout(NominalTypeDecl *nominalDecl) {
-  if (isa<SourceFile>(nominalDecl->getModuleScopeContext()))
-    DeclsToFinalize.insert(nominalDecl);
+void TypeChecker::requestClassLayout(ClassDecl *classDecl) {
+  if (isa<SourceFile>(classDecl->getModuleScopeContext()))
+    DeclsToFinalize.insert(classDecl);
 }
 
 void TypeChecker::requestSuperclassLayout(ClassDecl *classDecl) {
   if (auto *superclassDecl = classDecl->getSuperclassDecl()) {
     if (superclassDecl)
-      requestNominalLayout(superclassDecl);
+      requestClassLayout(superclassDecl);
   }
 }
 
-/// "Finalize" the type so that SILGen can make copies of it, call
-/// methods on it, etc. This requires forcing enough computation so
-/// that (for example) a class can layout its vtable or a struct can
-/// be laid out in memory.
-static void finalizeType(TypeChecker &TC, NominalTypeDecl *nominal) {
-  assert(!nominal->hasClangNode());
-  assert(isa<SourceFile>(nominal->getModuleScopeContext()));
-
-  if (auto *CD = dyn_cast<ClassDecl>(nominal)) {
-    // We need to add implicit initializers and dtors because it
-    // affects vtable layout.
-    TC.addImplicitConstructors(CD);
-    CD->addImplicitDestructor();
-  }
-
-  // Force lowering of stored properties.
-  (void) nominal->getStoredProperties();
-
-  if (isa<ClassDecl>(nominal) || isa<ProtocolDecl>(nominal)) {
-    for (auto *D : nominal->getMembers()) {
-      if (auto *ASD = dyn_cast<AbstractStorageDecl>(D))
-        TC.DeclsToFinalize.insert(ASD);
-    }
-  }
-
-  if (auto *CD = dyn_cast<ClassDecl>(nominal)) {
-    // We need the superclass vtable layout as well.
-    TC.requestSuperclassLayout(CD);
+void TypeChecker::finalizeDecl(ClassDecl *CD) {
+  if (Context.Stats)
+    Context.Stats->getFrontendCounters().NumDeclsFinalized++;
 
-    auto forceConformance = [&](ProtocolDecl *protocol) {
-      if (auto ref = TypeChecker::conformsToProtocol(
-            CD->getDeclaredInterfaceType(), protocol, CD,
-            ConformanceCheckFlags::SkipConditionalRequirements,
-            SourceLoc())) {
-        auto conformance = ref->getConcrete();
-        if (conformance->getDeclContext() == CD &&
-            conformance->getState() == ProtocolConformanceState::Incomplete) {
-          TC.checkConformance(conformance->getRootNormalConformance());
-        }
-      }
-    };
+  assert(!CD->hasClangNode());
+  assert(isa<SourceFile>(CD->getModuleScopeContext()));
 
-    // If the class is Encodable, Decodable or Hashable, force those
-    // conformances to ensure that the synthesized members appear in the vtable.
-    //
-    // FIXME: Generalize this to other protocols for which
-    // we can derive conformances.
-    forceConformance(TC.Context.getProtocol(KnownProtocolKind::Decodable));
-    forceConformance(TC.Context.getProtocol(KnownProtocolKind::Encodable));
-    forceConformance(TC.Context.getProtocol(KnownProtocolKind::Hashable));
-  }
+  validateDecl(CD);
 
-  if (auto PD = dyn_cast<ProtocolDecl>(nominal)) {
-    for (auto *inherited : PD->getInheritedProtocols())
-      TC.requestNominalLayout(inherited);
-  }
-}
+  // We need to add implicit initializers and dtors because it
+  // affects vtable layout.
+  addImplicitConstructors(CD);
+  CD->addImplicitDestructor();
 
-void TypeChecker::finalizeDecl(ValueDecl *decl) {
-  if (Context.Stats)
-    Context.Stats->getFrontendCounters().NumDeclsFinalized++;
+  // We need the superclass vtable layout as well.
+  requestSuperclassLayout(CD);
 
-  validateDecl(decl);
+  auto forceConformance = [&](ProtocolDecl *protocol) {
+    if (auto ref = TypeChecker::conformsToProtocol(
+          CD->getDeclaredInterfaceType(), protocol, CD,
+          ConformanceCheckFlags::SkipConditionalRequirements,
+          SourceLoc())) {
+      auto conformance = ref->getConcrete();
+      if (conformance->getDeclContext() == CD &&
+          conformance->getState() == ProtocolConformanceState::Incomplete) {
+        checkConformance(conformance->getRootNormalConformance());
+      }
+    }
+  };
 
-  if (auto nominal = dyn_cast<NominalTypeDecl>(decl)) {
-    finalizeType(*this, nominal);
-  } else if (auto storage = dyn_cast<AbstractStorageDecl>(decl)) {
-    addExpectedOpaqueAccessorsToStorage(storage);
-  }
+  // If the class is Encodable, Decodable or Hashable, force those
+  // conformances to ensure that the synthesized members appear in the vtable.
+  //
+  // FIXME: Generalize this to other protocols for which
+  // we can derive conformances.
+  forceConformance(Context.getProtocol(KnownProtocolKind::Decodable));
+  forceConformance(Context.getProtocol(KnownProtocolKind::Encodable));
+  forceConformance(Context.getProtocol(KnownProtocolKind::Hashable));
 }
 
 /// Determine whether this is a "pass-through" typealias, which has the
diff --git a/lib/Sema/TypeCheckDeclOverride.cpp b/lib/Sema/TypeCheckDeclOverride.cpp
index fd4b6097386ee..4675c254130f9 100644
--- a/lib/Sema/TypeCheckDeclOverride.cpp
+++ b/lib/Sema/TypeCheckDeclOverride.cpp
@@ -1041,7 +1041,7 @@ bool OverrideMatcher::checkOverride(ValueDecl *baseDecl,
     // Otherwise, if this is a subscript, validate that covariance is ok.
     // If the parent is non-mutable, it's okay to be covariant.
     auto parentSubscript = cast<SubscriptDecl>(baseDecl);
-    if (parentSubscript->getAccessor(AccessorKind::Set)) {
+    if (parentSubscript->supportsMutation()) {
       diags.diagnose(subscript, diag::override_mutable_covariant_subscript,
                      declTy, baseTy);
       diags.diagnose(baseDecl, diag::subscript_override_here);
@@ -1088,7 +1088,7 @@ bool OverrideMatcher::checkOverride(ValueDecl *baseDecl,
           IsSilentDifference = true;
 
     // The overridden property must not be mutable.
-    if (cast<AbstractStorageDecl>(baseDecl)->getAccessor(AccessorKind::Set) &&
+    if (cast<AbstractStorageDecl>(baseDecl)->supportsMutation() &&
         !IsSilentDifference) {
       diags.diagnose(property, diag::override_mutable_covariant_property,
                   property->getName(), parentPropertyTy, propertyTy);
@@ -1472,8 +1472,8 @@ isRedundantAccessorOverrideAvailabilityDiagnostic(ValueDecl *override,
   // Returns true if we will already diagnose a bad override
   // on the property's accessor of the given kind.
   auto accessorOverrideAlreadyDiagnosed = [&](AccessorKind kind) {
-    FuncDecl *overrideAccessor = overrideASD->getAccessor(kind);
-    FuncDecl *baseAccessor = baseASD->getAccessor(kind);
+    FuncDecl *overrideAccessor = overrideASD->getOpaqueAccessor(kind);
+    FuncDecl *baseAccessor = baseASD->getOpaqueAccessor(kind);
     if (overrideAccessor && baseAccessor &&
         !isAvailabilitySafeForOverride(overrideAccessor, baseAccessor)) {
       return true;
@@ -1557,8 +1557,8 @@ static bool checkSingleOverride(ValueDecl *override, ValueDecl *base) {
     // Make sure that the overriding property doesn't have storage.
     if ((overrideASD->hasStorage() ||
          overrideASD->getAttrs().hasAttribute<LazyAttr>()) &&
-        !(overrideASD->getAccessor(AccessorKind::WillSet) ||
-          overrideASD->getAccessor(AccessorKind::DidSet))) {
+        !(overrideASD->getParsedAccessor(AccessorKind::WillSet) ||
+          overrideASD->getParsedAccessor(AccessorKind::DidSet))) {
       bool downgradeToWarning = false;
       if (!ctx.isSwiftVersionAtLeast(5) &&
           overrideASD->getAttrs().hasAttribute<LazyAttr>()) {
@@ -1889,12 +1889,13 @@ OverriddenDeclsRequest::evaluate(Evaluator &evaluator, ValueDecl *decl) const {
         continue;
 
       // Find the base accessor; if there isn't one, we're done.
-      auto baseAccessor = baseASD->getAccessor(kind);
-      if (!baseAccessor) continue;
-
-      if (baseAccessor->hasForcedStaticDispatch())
+      auto baseAccessor = baseASD->getOpaqueAccessor(kind);
+      if (!baseAccessor)
         continue;
 
+      assert(!baseAccessor->hasForcedStaticDispatch() &&
+             "opaque accessor with forced static dispatch?");
+
       switch (kind) {
       case AccessorKind::Get:
       case AccessorKind::Read:
diff --git a/lib/Sema/TypeCheckPattern.cpp b/lib/Sema/TypeCheckPattern.cpp
index 1862a9b2b5243..429b4deec2a7c 100644
--- a/lib/Sema/TypeCheckPattern.cpp
+++ b/lib/Sema/TypeCheckPattern.cpp
@@ -809,8 +809,8 @@ static void requestLayoutForMetadataSources(TypeChecker &tc, Type type) {
     // parameter is of dependent type then the body of a function with said
     // parameter could potentially require the generic type's layout to
     // recover them.
-    if (auto *nominalDecl = type->getAnyNominal()) {
-      tc.requestNominalLayout(nominalDecl);
+    if (auto *classDecl = type->getClassOrBoundGenericClass()) {
+      tc.requestClassLayout(classDecl);
     }
   });
 }
diff --git a/lib/Sema/TypeCheckProtocol.cpp b/lib/Sema/TypeCheckProtocol.cpp
index 615ed3ce7df1f..a9377a6504f85 100644
--- a/lib/Sema/TypeCheckProtocol.cpp
+++ b/lib/Sema/TypeCheckProtocol.cpp
@@ -238,15 +238,17 @@ static bool checkObjCWitnessSelector(TypeChecker &tc, ValueDecl *req,
   // FIXME: Check property names!
 
   // Check the getter.
-  if (auto reqGetter = reqStorage->getAccessor(AccessorKind::Get)) {
-    auto *witnessGetter = witnessStorage->getAccessor(AccessorKind::Get);
+  if (auto reqGetter = reqStorage->getParsedAccessor(AccessorKind::Get)) {
+    auto *witnessGetter =
+      witnessStorage->getSynthesizedAccessor(AccessorKind::Get);
     if (checkObjCWitnessSelector(tc, reqGetter, witnessGetter))
       return true;
   }
 
   // Check the setter.
-  if (auto reqSetter = reqStorage->getAccessor(AccessorKind::Set)) {
-    auto *witnessSetter = witnessStorage->getAccessor(AccessorKind::Set);
+  if (auto reqSetter = reqStorage->getParsedAccessor(AccessorKind::Set)) {
+    auto *witnessSetter =
+      witnessStorage->getSynthesizedAccessor(AccessorKind::Set);
     if (checkObjCWitnessSelector(tc, reqSetter, witnessSetter))
       return true;
   }
@@ -264,48 +266,40 @@ static ParameterList *getParameterList(ValueDecl *value) {
 
 // Find a standin declaration to place the diagnostic at for the
 // given accessor kind.
-static ValueDecl *getStandinForAccessor(AbstractStorageDecl *witnessStorage,
+static ValueDecl *getStandinForAccessor(AbstractStorageDecl *witness,
                                         AccessorKind requirementKind) {
-  auto getExplicitAccessor = [&](AccessorKind kind) -> AccessorDecl* {
-    if (auto accessor = witnessStorage->getAccessor(kind)) {
-      if (!accessor->isImplicit())
-        return accessor;
-    }
-    return nullptr;
-  };
-
   // If the storage actually explicitly provides that accessor, great.
-  if (auto accessor = getExplicitAccessor(requirementKind))
+  if (auto accessor = witness->getParsedAccessor(requirementKind))
     return accessor;
 
   // If it didn't, check to see if it provides something else that corresponds
   // to the requirement.
   switch (requirementKind) {
   case AccessorKind::Get:
-    if (auto read = getExplicitAccessor(AccessorKind::Read))
+    if (auto read = witness->getParsedAccessor(AccessorKind::Read))
       return read;
-    if (auto addressor = getExplicitAccessor(AccessorKind::Address))
+    if (auto addressor = witness->getParsedAccessor(AccessorKind::Address))
       return addressor;
     break;
 
   case AccessorKind::Read:
-    if (auto getter = getExplicitAccessor(AccessorKind::Get))
+    if (auto getter = witness->getParsedAccessor(AccessorKind::Get))
       return getter;
-    if (auto addressor = getExplicitAccessor(AccessorKind::Address))
+    if (auto addressor = witness->getParsedAccessor(AccessorKind::Address))
       return addressor;
     break;
 
   case AccessorKind::Modify:
-    if (auto setter = getExplicitAccessor(AccessorKind::Set))
+    if (auto setter = witness->getParsedAccessor(AccessorKind::Set))
       return setter;
-    if (auto addressor = getExplicitAccessor(AccessorKind::MutableAddress))
+    if (auto addressor = witness->getParsedAccessor(AccessorKind::MutableAddress))
       return addressor;
     break;
 
   case AccessorKind::Set:
-    if (auto modify = getExplicitAccessor(AccessorKind::Modify))
+    if (auto modify = witness->getParsedAccessor(AccessorKind::Modify))
       return modify;
-    if (auto addressor = getExplicitAccessor(AccessorKind::MutableAddress))
+    if (auto addressor = witness->getParsedAccessor(AccessorKind::MutableAddress))
       return addressor;
     break;
 
@@ -317,7 +311,7 @@ static ValueDecl *getStandinForAccessor(AbstractStorageDecl *witnessStorage,
   }
 
   // Otherwise, just diagnose starting at the storage declaration itself.
-  return witnessStorage;
+  return witness;
 }
 
 RequirementMatch
@@ -2214,12 +2208,6 @@ void ConformanceChecker::recordWitness(ValueDecl *requirement,
   // Record this witness in the conformance.
   auto witness = match.getWitness(TC.Context);
   Conformance->setWitness(requirement, witness);
-
-  // Synthesize accessors for the protocol witness table to use.
-  if (auto storage = dyn_cast<AbstractStorageDecl>(witness.getDecl()))
-    TC.synthesizeWitnessAccessorsForStorage(
-                                        cast<AbstractStorageDecl>(requirement),
-                                        storage);
 }
 
 void ConformanceChecker::recordOptionalWitness(ValueDecl *requirement) {
@@ -3705,11 +3693,6 @@ void ConformanceChecker::resolveValueWitnesses() {
       auto witness = Conformance->getWitness(requirement).getDecl();
       if (!witness) return;
 
-      // Make sure that we finalize the witness, so we can emit this
-      // witness table.
-      if (isa<AbstractStorageDecl>(witness))
-        TC.DeclsToFinalize.insert(witness);
-
       // Objective-C checking for @objc requirements.
       if (requirement->isObjC() &&
           requirement->getFullName() == witness->getFullName() &&
@@ -5040,9 +5023,9 @@ void TypeChecker::checkConformancesInContext(DeclContext *dc,
           sf->ObjCUnsatisfiedOptReqs.emplace_back(dc, funcReq);
         } else {
           auto storageReq = cast<AbstractStorageDecl>(req);
-          if (auto getter = storageReq->getAccessor(AccessorKind::Get))
+          if (auto getter = storageReq->getParsedAccessor(AccessorKind::Get))
             sf->ObjCUnsatisfiedOptReqs.emplace_back(dc, getter);
-          if (auto setter = storageReq->getAccessor(AccessorKind::Set))
+          if (auto setter = storageReq->getParsedAccessor(AccessorKind::Set))
             sf->ObjCUnsatisfiedOptReqs.emplace_back(dc, setter);
         }
       }
@@ -5151,7 +5134,7 @@ swift::findWitnessedObjCRequirements(const ValueDecl *witness,
             auto *storageReq = dyn_cast<AbstractStorageDecl>(req);
             if (!storageReq)
               continue;
-            req = storageReq->getAccessor(*accessorKind);
+            req = storageReq->getOpaqueAccessor(*accessorKind);
             if (!req)
               continue;
           }
@@ -5169,10 +5152,10 @@ swift::findWitnessedObjCRequirements(const ValueDecl *witness,
         auto *storageFound = dyn_cast_or_null<AbstractStorageDecl>(found);
         if (!storageReq || !storageFound)
           continue;
-        req = storageReq->getAccessor(*accessorKind);
+        req = storageReq->getOpaqueAccessor(*accessorKind);
         if (!req)
           continue;
-        found = storageFound->getAccessor(*accessorKind);
+        found = storageFound->getOpaqueAccessor(*accessorKind);
       }
 
       // Determine whether the witness for this conformance is in fact
@@ -5343,12 +5326,6 @@ void DefaultWitnessChecker::recordWitness(
                                   const RequirementMatch &match) {
   Proto->setDefaultWitness(requirement,
                            match.getWitness(TC.Context));
-
-  // Synthesize accessors for the protocol witness table to use.
-  if (auto storage = dyn_cast<AbstractStorageDecl>(match.Witness))
-    TC.synthesizeWitnessAccessorsForStorage(
-                                        cast<AbstractStorageDecl>(requirement),
-                                        storage);
 }
 
 void TypeChecker::inferDefaultWitnesses(ProtocolDecl *proto) {
diff --git a/lib/Sema/TypeChecker.h b/lib/Sema/TypeChecker.h
index ca4ac206a3b0e..a480b69d41d8a 100644
--- a/lib/Sema/TypeChecker.h
+++ b/lib/Sema/TypeChecker.h
@@ -556,7 +556,7 @@ class TypeChecker final : public LazyResolver {
   /// The list of declarations that we've done at least partial validation
   /// of during type-checking, but which will need to be finalized before
   /// we can hand them off to SILGen etc.
-  llvm::SetVector<ValueDecl *> DeclsToFinalize;
+  llvm::SetVector<ClassDecl *> DeclsToFinalize;
 
   /// Track the index of the next declaration that needs to be finalized,
   /// from the \c DeclsToFinalize set.
@@ -810,7 +810,7 @@ class TypeChecker final : public LazyResolver {
 
   /// Request that the given class needs to have all members validated
   /// after everything in the translation unit has been processed.
-  void requestNominalLayout(NominalTypeDecl *nominalDecl);
+  void requestClassLayout(ClassDecl *classDecl);
 
   /// Request that the superclass of the given class, if any, needs to have
   /// all members validated after everything in the translation unit has
@@ -819,7 +819,7 @@ class TypeChecker final : public LazyResolver {
 
   /// Perform final validation of a declaration after everything in the
   /// translation unit has been processed.
-  void finalizeDecl(ValueDecl *D);
+  void finalizeDecl(ClassDecl *CD);
 
   /// Resolve a reference to the given type declaration within a particular
   /// context.
@@ -1172,12 +1172,6 @@ class TypeChecker final : public LazyResolver {
   /// target.
   void synthesizeMemberForLookup(NominalTypeDecl *target, DeclName member);
 
-  /// The specified AbstractStorageDecl \c storage was just found to satisfy
-  /// the protocol property \c requirement.  Ensure that it has the full
-  /// complement of accessors.
-  void synthesizeWitnessAccessorsForStorage(AbstractStorageDecl *requirement,
-                                            AbstractStorageDecl *storage);
-
   /// Pre-check the expression, validating any types that occur in the
   /// expression and folding sequence expressions.
   bool preCheckExpression(Expr *&expr, DeclContext *dc);
diff --git a/lib/Serialization/Serialization.cpp b/lib/Serialization/Serialization.cpp
index 3f932e6791434..6b7d4f86994e0 100644
--- a/lib/Serialization/Serialization.cpp
+++ b/lib/Serialization/Serialization.cpp
@@ -4891,15 +4891,6 @@ void Serializer::writeAST(ModuleOrSourceFile DC,
 
       orderedTopLevelDecls.push_back(addDeclRef(D));
 
-      // If this is a global variable, force the accessors to be
-      // serialized.
-      if (auto VD = dyn_cast<VarDecl>(D)) {
-        if (auto *getter = VD->getAccessor(swift::AccessorKind::Get))
-          addDeclRef(getter);
-        if (auto *setter = VD->getAccessor(swift::AccessorKind::Set))
-          addDeclRef(setter);
-      }
-
       // If this nominal type has associated top-level decls for a
       // derived conformance (for example, ==), force them to be
       // serialized.
diff --git a/lib/TBDGen/TBDGen.cpp b/lib/TBDGen/TBDGen.cpp
index c310794403ac5..6767de6a59f93 100644
--- a/lib/TBDGen/TBDGen.cpp
+++ b/lib/TBDGen/TBDGen.cpp
@@ -159,8 +159,8 @@ void TBDGenVisitor::addConformances(DeclContext *DC) {
             auto witnessStorage = cast<AbstractStorageDecl>(witnessDecl);
             storage->visitOpaqueAccessors([&](AccessorDecl *reqtAccessor) {
               auto witnessAccessor =
-                witnessStorage->getAccessor(reqtAccessor->getAccessorKind());
-              assert(witnessAccessor && "no corresponding witness accessor?");
+                witnessStorage->getSynthesizedAccessor(
+                  reqtAccessor->getAccessorKind());
               addSymbolIfNecessary(reqtAccessor, witnessAccessor);
             });
           }
diff --git a/test/api-digester/Outputs/stability-stdlib-abi.asserts.additional.swift.expected b/test/api-digester/Outputs/stability-stdlib-abi.asserts.additional.swift.expected
index 05c686d12cf91..46dec10978ec8 100644
--- a/test/api-digester/Outputs/stability-stdlib-abi.asserts.additional.swift.expected
+++ b/test/api-digester/Outputs/stability-stdlib-abi.asserts.additional.swift.expected
@@ -6,3 +6,4 @@ Struct _GlobalRuntimeFunctionCountersState is a new API without @available attri
 Struct _ObjectRuntimeFunctionCountersState is a new API without @available attribute
 Struct _RuntimeFunctionCounters is a new API without @available attribute
 Func _measureRuntimeFunctionCountersDiffs(objects:_:) is a new API without @available attribute
+Accessor Slice.subscript(_:).Read() has been removed
diff --git a/test/multifile/Inputs/inlinable-other.swift b/test/multifile/Inputs/inlinable-other.swift
new file mode 100644
index 0000000000000..95d47830594c8
--- /dev/null
+++ b/test/multifile/Inputs/inlinable-other.swift
@@ -0,0 +1,4 @@
+public struct OtherStruct {
+  public internal(set) static var staticProp = 123
+  // expected-note@-1 {{setter for 'staticProp' is not '@usableFromInline' or public}}
+}
diff --git a/test/multifile/Inputs/protocol-conformance-let-other.swift b/test/multifile/Inputs/protocol-conformance-let-other.swift
index 82a353093b657..847398b3ac021 100644
--- a/test/multifile/Inputs/protocol-conformance-let-other.swift
+++ b/test/multifile/Inputs/protocol-conformance-let-other.swift
@@ -1,4 +1,3 @@
 public protocol P {
   let x: Int
-  // expected-error@-1 {{immutable property requirement must be declared as 'var' with a '{ get }' specifier}}
 }
diff --git a/test/multifile/Inputs/protocol-conformance-objc-other.swift b/test/multifile/Inputs/protocol-conformance-objc-other.swift
new file mode 100644
index 0000000000000..2e7142bc48b86
--- /dev/null
+++ b/test/multifile/Inputs/protocol-conformance-objc-other.swift
@@ -0,0 +1,5 @@
+import Foundation
+
+public class Pony {
+  public var hindEnd: Int = 0
+}
diff --git a/test/multifile/inlinable.swift b/test/multifile/inlinable.swift
new file mode 100644
index 0000000000000..08ec4b959fabe
--- /dev/null
+++ b/test/multifile/inlinable.swift
@@ -0,0 +1,10 @@
+// RUN: %target-swift-frontend -typecheck -verify %s %S/Inputs/inlinable-other.swift
+
+@frozen public struct HasInitExpr {
+  public var hasInlinableInit = mutatingFunc(&OtherStruct.staticProp)
+  // expected-warning@-1 {{setter for 'staticProp' is internal and should not be referenced from a property initializer in a '@frozen' type}}
+}
+
+public func mutatingFunc(_: inout Int) -> Int {
+  return 0
+}
diff --git a/test/multifile/protocol-conformance-objc.swift b/test/multifile/protocol-conformance-objc.swift
new file mode 100644
index 0000000000000..b90ffc4617a6d
--- /dev/null
+++ b/test/multifile/protocol-conformance-objc.swift
@@ -0,0 +1,12 @@
+// RUN: %target-swift-frontend -sdk %sdk -emit-ir -primary-file %s %S/Inputs/protocol-conformance-objc-other.swift -module-name test
+
+// REQUIRES: objc_interop
+
+import Foundation
+
+@objc protocol Horse {
+  var hindEnd: Int { get set }
+}
+
+extension Pony : Horse {}
+