[SymbolGraphGen] check implicit clang decls for having extension parents

lib/SymbolGraphGen/SymbolGraphASTWalker.cpp

@@ -308,7 +308,7 @@ bool SymbolGraphASTWalker::walkToDeclPre(Decl *D, CharSourceRange Range) {
 
       // We also might establish some synthesized members because we
       // extended an external type.
-      if (ExtendedNominal->getModuleContext() != &M) {
+      if (!areModulesEqual(ExtendedNominal->getModuleContext(), &M)) {
         ExtendedSG->recordConformanceSynthesizedMemberRelationships(Source);
       }
     }
@@ -341,10 +341,13 @@ bool SymbolGraphASTWalker::walkToDeclPre(Decl *D, CharSourceRange Range) {
   // symbol, regardless of which class it's actually appearing on. To prevent
   // multiple of these symbols colliding with each other, treat them as
   // synthesized symbols and use their parent type as the base type.
-  if (VD->isImplicit() && VD->hasClangNode() &&
-      VD->getClangNode().getAsDecl()) {
-    if (const auto *Parent =
-            dyn_cast_or_null<NominalTypeDecl>(VD->getDeclContext())) {
+  if (VD->isImplicit() && VD->getClangDecl()) {
+    const NominalTypeDecl *Parent = dyn_cast_or_null<NominalTypeDecl>(VD->getDeclContext());
+    if (!Parent) {
+      if (const auto *ParentExt = dyn_cast_or_null<ExtensionDecl>(VD->getDeclContext()))
+        Parent = ParentExt->getExtendedNominal();
+    }
+    if (Parent) {
       SG->recordNode(Symbol(SG, VD, Parent));
       return true;
     }

test/SymbolGraph/ClangImporter/ObjCInitializer.swift

@@ -0,0 +1,28 @@
+// REQUIRES: objc_interop
+
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+// RUN: %target-swift-symbolgraph-extract -sdk %clang-importer-sdk -module-name ObjCInitializer -Fsystem %t -output-dir %t -pretty-print -v
+// RUN: %FileCheck %s --input-file %t/ObjCInitializer.symbols.json
+// RUN: %FileCheck %s --input-file %t/ObjCInitializer.symbols.json --check-prefix SYNTH
+
+//--- ObjCInitializer.framework/Modules/module.modulemap
+framework module ObjCInitializer [system] {
+    header "ObjCInitializer.h"
+}
+
+//--- ObjCInitializer.framework/Headers/ObjCInitializer.h
+@import Foundation;
+
+@interface NSScrubberLayoutAttributes : NSObject <NSCopying>
+
+// This initializer gets imported twice - once as `init(forItemAt:)` and once as
+// `init(forItemAtIndex:)`. Make sure one of them gets a synthesized USR
+// CHECK:     "precise": "c:objc(cs)NSScrubberLayoutAttributes(cm)layoutAttributesForItemAtIndex:"
+// CHECK-NOT: "precise": "c:objc(cs)NSScrubberLayoutAttributes(cm)layoutAttributesForItemAtIndex:"
+// SYNTH:     "precise": "c:objc(cs)NSScrubberLayoutAttributes(cm)layoutAttributesForItemAtIndex:::SYNTHESIZED::c:objc(cs)NSScrubberLayoutAttributes",
+// SYNTH-NOT: "precise": "c:objc(cs)NSScrubberLayoutAttributes(cm)layoutAttributesForItemAtIndex:::SYNTHESIZED::c:objc(cs)NSScrubberLayoutAttributes",
++ (instancetype)layoutAttributesForItemAtIndex:(NSInteger)index;
+
+@end

test/SymbolGraph/ClangImporter/ProtocolInitializer.swift

@@ -0,0 +1,32 @@
+// REQUIRES: objc_interop
+
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+// RUN: %target-swift-symbolgraph-extract -sdk %clang-importer-sdk -module-name ProtocolInitializer -I %t/ProtocolInitializer -output-dir %t -pretty-print -v
+// RUN: %FileCheck %s --input-file %t/ProtocolInitializer.symbols.json
+
+// the initializer's base USR should only appear as the source of one relationship
+// CHECK: "source": "c:objc(pl)MyProtocol(im)initWithSomeNumber:"
+// CHECK-NOT: "source": "c:objc(pl)MyProtocol(im)initWithSomeNumber:"
+
+//--- ProtocolInitializer/module.modulemap
+module ProtocolInitializer {
+    header "ProtocolInitializer.h"
+}
+
+//--- ProtocolInitializer/ProtocolInitializer.h
+@import Foundation;
+
+@protocol MyProtocol <NSObject>
+
+@optional
+- (nullable id)initWithSomeNumber:(NSInteger)number;
+
+@end
+
+@interface MyClass : NSObject
+@end
+
+@interface MyClass () <MyProtocol>
+@end