Merge pull request #25445 from slavapestov/testable-protocol-override

Fix crash when refining protocol from a testable import

Author: slavapestov

include/swift/AST/Decl.h

@@ -7190,8 +7190,7 @@ inline bool Decl::isPotentiallyOverridable() const {
       isa<SubscriptDecl>(this) ||
       isa<FuncDecl>(this) ||
       isa<DestructorDecl>(this)) {
-    return getDeclContext()->getSelfClassDecl() ||
-           isa<ProtocolDecl>(getDeclContext());
+    return getDeclContext()->getSelfClassDecl();
   } else {
     return false;
   }

lib/Sema/TypeCheckDeclOverride.cpp

@@ -831,10 +831,14 @@ static void checkOverrideAccessControl(ValueDecl *baseDecl, ValueDecl *decl,
   if (ctx.isAccessControlDisabled())
     return;
 
+  if (isa<ProtocolDecl>(decl->getDeclContext()))
+    return;
+
   auto &diags = ctx.Diags;
 
   auto dc = decl->getDeclContext();
   auto classDecl = dc->getSelfClassDecl();
+  assert(classDecl != nullptr && "Should have ruled out protocols above");
 
   bool isAccessor = isa<AccessorDecl>(decl);
 
@@ -851,8 +855,7 @@ static void checkOverrideAccessControl(ValueDecl *baseDecl, ValueDecl *decl,
   if (!isAccessor &&
       !baseHasOpenAccess &&
       baseDecl->getModuleContext() != decl->getModuleContext() &&
-      !isa<ConstructorDecl>(decl) &&
-      !isa<ProtocolDecl>(decl->getDeclContext())) {
+      !isa<ConstructorDecl>(decl)) {
     // NSObject.hashValue was made non-overridable in Swift 5; one should
     // override NSObject.hash instead.
     if (isNSObjectHashValue(baseDecl)) {
@@ -875,8 +878,7 @@ static void checkOverrideAccessControl(ValueDecl *baseDecl, ValueDecl *decl,
     }
     diags.diagnose(baseDecl, diag::overridden_here);
 
-  } else if (!isa<ConstructorDecl>(decl) &&
-             !isa<ProtocolDecl>(decl->getDeclContext())) {
+  } else if (!isa<ConstructorDecl>(decl)) {
     auto matchAccessScope =
       baseDecl->getFormalAccessScope(dc);
     auto classAccessScope =

test/multifile/Inputs/protocol-override-other.swift

@@ -0,0 +1,3 @@
+protocol Base {
+  var foo: String { get }
+}

test/multifile/protocol-override.swift

@@ -0,0 +1,9 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module-path %t/other.swiftmodule %S/Inputs/protocol-override-other.swift -module-name other -enable-testing
+// RUN: %target-swift-frontend -typecheck %s -I %t
+
+@testable import other
+
+protocol Sub : Base {
+  var foo: String { get set }
+}