Merge pull request #19378 from slavapestov/index-while-building-crash

Index: Don't crash if an optional requirement is missing its witness

Author: slavapestov

lib/Index/Index.cpp

@@ -661,6 +661,9 @@ bool IndexSwiftASTWalker::handleValueWitnesses(Decl *D, SmallVectorImpl<ValueWit
         return;
 
       auto *decl = witness.getDecl();
+      if (decl == nullptr)
+        return;
+
       if (decl->getDeclContext() == DC) {
         explicitValueWitnesses.push_back(ValueWitness{decl, req});
       } else {

test/Index/objc_conformances.swift

@@ -0,0 +1,17 @@
+// RUN: %target-swift-ide-test(mock-sdk: %clang-importer-sdk) -print-indexed-symbols -source-filename %s | %FileCheck %s
+// REQUIRES: objc_interop
+
+import Foundation
+
+// Make sure we properly handle missing optional requirements.
+@objc protocol P {
+  @objc optional func f()
+  func g()
+}
+
+class C : P {
+  @objc func g() {}
+  // CHECK: [[@LINE-1]]:14 | instance-method/Swift | g() | s:14swift_ide_test1CC1gyyF | Def,Dyn,RelChild,RelOver | rel: 2
+  // CHECK: RelOver | instance-method/Swift | g() | c:@M@swift_ide_test@objc(pl)P(im)g
+  // CHECK: RelChild | class/Swift | C | s:14swift_ide_test1CC
+}