Require objcImplementation members to avoid vtable

They either must be @objc dynamic (the dynamic is implicit) or final.

include/swift/AST/DiagnosticsSema.def

@@ -1512,6 +1512,18 @@ NOTE(attr_objc_implementation_fixit_remove_category_name,none,
      "remove arguments to implement the main '@interface' for this class",
      ())
 
+ERROR(member_of_objc_implementation_not_objc_or_final,none,
+      "%0 %1 does not match any %0 declared in the headers for %2; did you use "
+      "the %0's Swift name?",
+      (DescriptiveDeclKind, ValueDecl *, ValueDecl *))
+NOTE(fixit_add_objc_for_objc_implementation,none,
+     "add '@objc' to define an Objective-C-compatible %0 not declared in "
+     "the header",
+     (DescriptiveDeclKind))
+NOTE(fixit_add_final_for_objc_implementation,none,
+     "add 'final' to define a Swift %0 that cannot be overridden",
+     (DescriptiveDeclKind))
+
 ERROR(cdecl_not_at_top_level,none,
       "@_cdecl can only be applied to global functions", ())
 ERROR(cdecl_empty_name,none,

lib/Sema/TypeCheckDecl.cpp

@@ -987,6 +987,12 @@ IsDynamicRequest::evaluate(Evaluator &evaluator, ValueDecl *decl) const {
   if (isa<ExtensionDecl>(dc) && dc->getSelfClassDecl())
     return true;
 
+  // @objc declarations in @_objcImplementation extensions are implicitly
+  // dynamic.
+  if (auto ED = dyn_cast_or_null<ExtensionDecl>(dc->getAsDecl()))
+    if (ED->isObjCImplementation())
+      return true;
+
   // If any of the declarations overridden by this declaration are dynamic
   // or were imported from Objective-C, this declaration is dynamic.
   // Don't do this if the declaration is not exposed to Objective-C; that's

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -1213,6 +1213,29 @@ static void checkDynamicSelfType(ValueDecl *decl, Type type) {
   }
 }
 
+/// Check that, if this declaration is a member of an `@_objcImplementation`
+/// extension, it is either `final` or `@objc` (which may have been inferred by
+/// checking whether it shadows an imported declaration).
+static void checkObjCImplementationMemberAvoidsVTable(ValueDecl *VD) {
+  auto ED = dyn_cast<ExtensionDecl>(VD->getDeclContext());
+  if (!ED || !ED->isObjCImplementation()) return;
+
+  if (VD->isSemanticallyFinal() || VD->isObjC()) return;
+
+  auto &diags = VD->getASTContext().Diags;
+  diags.diagnose(VD, diag::member_of_objc_implementation_not_objc_or_final,
+                 VD->getDescriptiveKind(), VD, ED->getExtendedNominal());
+
+  if (canBeRepresentedInObjC(VD))
+    diags.diagnose(VD, diag::fixit_add_objc_for_objc_implementation,
+                   VD->getDescriptiveKind())
+        .fixItInsert(VD->getAttributeInsertionLoc(false), "@objc ");
+
+  diags.diagnose(VD, diag::fixit_add_final_for_objc_implementation,
+                 VD->getDescriptiveKind())
+      .fixItInsert(VD->getAttributeInsertionLoc(true), "final ");
+}
+
 /// Build a default initializer string for the given pattern.
 ///
 /// This string is suitable for display in diagnostics.
@@ -1836,6 +1859,10 @@ public:
       (void) VD->isObjC();
       (void) VD->isDynamic();
 
+      // If this is in an `@_objcImplementation` extension, check whether it's
+      // valid there.
+      checkObjCImplementationMemberAvoidsVTable(VD);
+
       // Check for actor isolation of top-level and local declarations.
       // Declarations inside types are handled in checkConformancesInContext()
       // to avoid cycles involving associated type inference.

test/decl/ext/objc_implementation.swift

@@ -5,6 +5,9 @@
 @_objcImplementation extension ObjCClass {
   func method(fromHeader1: CInt) {
     // FIXME: OK, provides an implementation for the header's method.
+    // expected-error@-2 {{instance method 'method(fromHeader1:)' does not match any instance method declared in the headers for 'ObjCClass'; did you use the instance method's Swift name?}}
+    // expected-note@-3 {{add '@objc' to define an Objective-C-compatible instance method not declared in the header}} {{3-3=@objc }}
+    // expected-note@-4 {{add 'final' to define a Swift instance method that cannot be overridden}} {{3-3=final }}
   }
 
   @objc func method(fromHeader2: CInt) {
@@ -13,6 +16,9 @@
 
   func categoryMethod(fromHeader3: CInt) {
     // FIXME: Should complain about the wrong category
+    // expected-error@-2 {{instance method 'categoryMethod(fromHeader3:)' does not match any instance method declared in the headers for 'ObjCClass'; did you use the instance method's Swift name?}}
+    // expected-note@-3 {{add '@objc' to define an Objective-C-compatible instance method not declared in the header}} {{3-3=@objc }}
+    // expected-note@-4 {{add 'final' to define a Swift instance method that cannot be overridden}} {{3-3=final }}
   }
 
   @objc fileprivate func methodNot(fromHeader1: CInt) {
@@ -24,7 +30,9 @@
   }
 
   func methodNot(fromHeader3: CInt) {
-    // FIXME: Should complain about unmatched, un-attributed method
+    // expected-error@-1 {{instance method 'methodNot(fromHeader3:)' does not match any instance method declared in the headers for 'ObjCClass'; did you use the instance method's Swift name?}}
+    // expected-note@-2 {{add '@objc' to define an Objective-C-compatible instance method not declared in the header}} {{3-3=@objc }}
+    // expected-note@-3 {{add 'final' to define a Swift instance method that cannot be overridden}} {{3-3=final }}
   }
 }
 
@@ -32,10 +40,19 @@
 @_objcImplementation(PresentAdditions) extension ObjCClass {
   func method(fromHeader3: CInt) {
     // FIXME: Should complain about wrong category
+    // expected-error@-2 {{instance method 'method(fromHeader3:)' does not match any instance method declared in the headers for 'ObjCClass'; did you use the instance method's Swift name?}}
+    // expected-note@-3 {{add '@objc' to define an Objective-C-compatible instance method not declared in the header}} {{3-3=@objc }}
+    // expected-note@-4 {{add 'final' to define a Swift instance method that cannot be overridden}} {{3-3=final }}
   }
 
   func categoryMethod(fromHeader1: CInt) {
     // FIXME: OK, provides an implementation for the header's method.
+    // expected-error@-2 {{instance method 'categoryMethod(fromHeader1:)' does not match any instance method declared in the headers for 'ObjCClass'; did you use the instance method's Swift name?}}
+    // expected-note@-3 {{add '@objc' to define an Objective-C-compatible instance method not declared in the header}} {{3-3=@objc }}
+    // expected-note@-4 {{add 'final' to define a Swift instance method that cannot be overridden}} {{3-3=final }}
+  }
+
+  @objc func categoryMethod(fromHeader2: CInt) {
     // OK, provides an implementation for the header's method.
   }
 
@@ -48,7 +65,9 @@
   }
 
   func categoryMethodNot(fromHeader3: CInt) {
-    // FIXME: Should complain about unmatched, un-attributed method
+    // expected-error@-1 {{instance method 'categoryMethodNot(fromHeader3:)' does not match any instance method declared in the headers for 'ObjCClass'; did you use the instance method's Swift name?}}
+    // expected-note@-2 {{add '@objc' to define an Objective-C-compatible instance method not declared in the header}} {{3-3=@objc }}
+    // expected-note@-3 {{add 'final' to define a Swift instance method that cannot be overridden}} {{3-3=final }}
   }
 }
 
@@ -72,3 +91,23 @@
 
 @_objcImplementation(WTF) extension SwiftClass {} // expected
 // expected-error@-1 {{'@_objcImplementation' cannot be used to extend class 'SwiftClass' because it was defined by a Swift 'class' declaration, not an imported Objective-C '@interface' declaration}} {{1-27=}}
+
+func usesAreNotAmbiguous(obj: ObjCClass) {
+  obj.method(fromHeader1: 1)
+  obj.method(fromHeader2: 2)
+  obj.method(fromHeader3: 3)
+  obj.method(fromHeader4: 4)
+
+  obj.methodNot(fromHeader1: 1)
+  obj.methodNot(fromHeader2: 2)
+  obj.methodNot(fromHeader3: 3)
+
+  obj.categoryMethod(fromHeader1: 1)
+  obj.categoryMethod(fromHeader2: 2)
+  obj.categoryMethod(fromHeader3: 3)
+  obj.categoryMethod(fromHeader4: 4)
+
+  obj.categoryMethodNot(fromHeader1: 1)
+  obj.categoryMethodNot(fromHeader2: 2)
+  obj.categoryMethodNot(fromHeader3: 3)
+}