AST: Filter out some Obj-C overrides when MemberImportVisibility is enabled.

Unlike in Swift, Obj-C allows method overrides to be declared in extensions
(categories), even outside of the module that defines the type that is being
extended. When MemberImportVisibility is enabled, these overrides must be
filtered out to prevent them from hijacking name lookup and causing the
compiler to insist that the module that defines the extension be imported.

Resolves rdar://145329988.

Author: tshortli

lib/AST/NameLookup.cpp

@@ -2388,6 +2388,8 @@ static bool isAcceptableLookupResult(const DeclContext *dc, NLOptions options,
                                      ValueDecl *decl,
                                      bool onlyCompleteObjectInits,
                                      bool requireImport) {
+  auto &ctx = dc->getASTContext();
+
   // Filter out designated initializers, if requested.
   if (onlyCompleteObjectInits) {
     if (auto ctor = dyn_cast<ConstructorDecl>(decl)) {
@@ -2405,19 +2407,43 @@ static bool isAcceptableLookupResult(const DeclContext *dc, NLOptions options,
   }
 
   // Check access.
-  if (!(options & NL_IgnoreAccessControl) &&
-      !dc->getASTContext().isAccessControlDisabled()) {
+  if (!(options & NL_IgnoreAccessControl) && !ctx.isAccessControlDisabled()) {
     bool allowUsableFromInline = options & NL_IncludeUsableFromInline;
     if (!decl->isAccessibleFrom(dc, /*forConformance*/ false,
                                 allowUsableFromInline))
       return false;
   }
 
-  // Check that there is some import in the originating context that makes this
-  // decl visible.
-  if (requireImport && !(options & NL_IgnoreMissingImports))
-    if (!dc->isDeclImported(decl))
-      return false;
+  if (requireImport) {
+    // Check that there is some import in the originating context that makes
+    // this decl visible.
+    if (!(options & NL_IgnoreMissingImports)) {
+      if (!dc->isDeclImported(decl))
+        return false;
+    }
+
+    // Unlike in Swift, Obj-C allows method overrides to be declared in
+    // extensions (categories), even outside of the module that defines the
+    // type that is being extended. When MemberImportVisibility is enabled,
+    // if these overrides are not filtered out they can hijack name
+    // lookup and cause the compiler to insist that the module that defines
+    // the extension be imported, contrary to developer expectations.
+    //
+    // Filter results belonging to these extensions out, even when ignoring
+    // missing imports, if we're in a context that requires imports to access
+    // member declarations.
+    if (decl->getOverriddenDecl()) {
+      if (auto *extension = dyn_cast<ExtensionDecl>(decl->getDeclContext())) {
+        if (auto *nominal = extension->getExtendedNominal()) {
+          auto extensionMod = extension->getModuleContext();
+          auto nominalMod = nominal->getModuleContext();
+          if (!extensionMod->isSameModuleLookingThroughOverlays(nominalMod) &&
+              !dc->isDeclImported(extension))
+            return false;
+        }
+      }
+    }
+  }
 
   // Check that it has the appropriate ABI role.
   if (!ABIRoleInfo(decl).matchesOptions(options))

test/NameLookup/Inputs/MemberImportVisibility/Categories_A.h

@@ -1,6 +1,13 @@
 @import Foundation;
 
-@interface X
+@interface Base
+- (void)overriddenInOverlayForA __attribute__((deprecated("Categories_A.h")));
+- (void)overriddenInOverlayForB __attribute__((deprecated("Categories_A.h")));
+- (void)overriddenInOverlayForC __attribute__((deprecated("Categories_A.h")));
+- (void)overriddenInSubclassInOverlayForC __attribute__((deprecated("Categories_A.h")));
+@end
+
+@interface X : Base
 @end
 
 @interface X (A)

test/NameLookup/Inputs/MemberImportVisibility/Categories_A.swift

@@ -3,4 +3,7 @@
 extension X {
   public func fromOverlayForA() {}
   @objc public func fromOverlayForAObjC() {}
+
+  @available(*, deprecated, message: "Categories_A.swift")
+  public override func overriddenInOverlayForA() {}
 }

test/NameLookup/Inputs/MemberImportVisibility/Categories_B.swift

@@ -3,4 +3,7 @@
 extension X {
   public func fromOverlayForB() {}
   @objc public func fromOverlayForBObjC() {}
+
+  @available(*, deprecated, message: "Categories_B.swift")
+  public override func overriddenInOverlayForB() {}
 }

test/NameLookup/Inputs/MemberImportVisibility/Categories_C.h

@@ -3,3 +3,7 @@
 @interface X (C)
 - (void)fromC;
 @end
+
+@interface SubclassFromC : X
+- (instancetype)init;
+@end

test/NameLookup/Inputs/MemberImportVisibility/Categories_C.swift

@@ -3,4 +3,12 @@
 extension X {
   public func fromOverlayForC() {}
   @objc public func fromOverlayForCObjC() {}
+
+  @available(*, deprecated, message: "Categories_C.swift")
+  public override func overriddenInOverlayForC() {}
+}
+
+extension SubclassFromC {
+  @available(*, deprecated, message: "Categories_C.swift")
+  public override func overriddenInSubclassInOverlayForC() {}
 }

test/NameLookup/Inputs/MemberImportVisibility/Categories_E.swift

@@ -1,2 +1,4 @@
 import Categories_C
 import Categories_D.Submodule
+
+public func makeSubclassFromC() -> SubclassFromC { SubclassFromC() }

test/NameLookup/Inputs/MemberImportVisibility/ObjCOverloads/Branch.h

@@ -0,0 +1,9 @@
+@import Root;
+
+@interface BranchObject : RootObject
+- (void)overridden1 __attribute__((deprecated("Branch.h")));
+@end
+
+@interface BranchObject (Branch)
+- (void)overridden3 __attribute__((deprecated("Branch.h")));
+@end

test/NameLookup/Inputs/MemberImportVisibility/ObjCOverloads/Fruit.h

@@ -0,0 +1,5 @@
+@import Branch;
+
+@interface FruitObject : BranchObject
+- (void)overridden1 __attribute__((deprecated("Fruit.h")));
+@end

test/NameLookup/Inputs/MemberImportVisibility/ObjCOverloads/Leaf.h

@@ -0,0 +1,14 @@
+@import Branch;
+
+@interface LeafObject : BranchObject
+- (void)overridden1 __attribute__((deprecated("Leaf.h")));
+@end
+
+@interface BranchObject (Leaf)
+- (void)overridden2 __attribute__((deprecated("Leaf.h")));
+@end
+
+@interface LeafObject (Leaf)
+- (void)overridden3 __attribute__((deprecated("Leaf.h")));
+@end
+