Index: lib/Sema/SemaAccess.cpp
===================================================================
--- lib/Sema/SemaAccess.cpp
+++ lib/Sema/SemaAccess.cpp
@@ -11,6 +11,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/Basic/Specifiers.h"
 #include "clang/Sema/SemaInternal.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/CXXInheritance.h"
@@ -1856,29 +1857,31 @@
   }
 }
 
-/// Checks access to Decl from the given class. The check will take access
+/// Checks access to Target from the given class. The check will take access
 /// specifiers into account, but no member access expressions and such.
 ///
-/// \param Decl the declaration to check if it can be accessed
+/// \param Target the declaration to check if it can be accessed
 /// \param Ctx the class/context from which to start the search
-/// \return true if the Decl is accessible from the Class, false otherwise.
-bool Sema::IsSimplyAccessible(NamedDecl *Decl, DeclContext *Ctx) {
+/// \return true if the Target is accessible from the Class, false otherwise.
+bool Sema::IsSimplyAccessible(NamedDecl *Target, DeclContext *Ctx) {
   if (CXXRecordDecl *Class = dyn_cast<CXXRecordDecl>(Ctx)) {
-    if (!Decl->isCXXClassMember())
+    if (!Target->isCXXClassMember())
       return true;
 
+    if (Target->getAccess() == AS_public)
+      return true;
     QualType qType = Class->getTypeForDecl()->getCanonicalTypeInternal();
+    // The unprivileged access is AS_none as we don't know how the member was
+    // accessed, which is described by the access in DeclAccessPair.
+    // `IsAccessible` will examine the actual access of Target (i.e.
+    // Decl->getAccess()) when calculating the access.
     AccessTarget Entity(Context, AccessedEntity::Member, Class,
-                        DeclAccessPair::make(Decl, Decl->getAccess()),
-                        qType);
-    if (Entity.getAccess() == AS_public)
-      return true;
-
+                        DeclAccessPair::make(Target, AS_none), qType);
     EffectiveContext EC(CurContext);
     return ::IsAccessible(*this, EC, Entity) != ::AR_inaccessible;
   }
-  
-  if (ObjCIvarDecl *Ivar = dyn_cast<ObjCIvarDecl>(Decl)) {
+
+  if (ObjCIvarDecl *Ivar = dyn_cast<ObjCIvarDecl>(Target)) {
     // @public and @package ivars are always accessible.
     if (Ivar->getCanonicalAccessControl() == ObjCIvarDecl::Public ||
         Ivar->getCanonicalAccessControl() == ObjCIvarDecl::Package)
Index: lib/Sema/SemaCodeComplete.cpp
===================================================================
--- lib/Sema/SemaCodeComplete.cpp
+++ lib/Sema/SemaCodeComplete.cpp
@@ -1303,8 +1303,33 @@
     void FoundDecl(NamedDecl *ND, NamedDecl *Hiding, DeclContext *Ctx,
                    bool InBaseClass) override {
       bool Accessible = true;
-      if (Ctx)
-        Accessible = Results.getSema().IsSimplyAccessible(ND, Ctx);
+      if (Ctx) {
+        DeclContext *AccessingCtx = Ctx;
+        // If ND comes from a base class, set the naming class back to the
+        // derived class if the search starts from the derived class (i.e.
+        // InBaseClass is true).
+        //
+        // Example:
+        //   class B { protected: int X; }
+        //   class D : public B { void f(); }
+        //   void D::f() { this->^; }
+        // The completion after "this->" will have `InBaseClass` set to true and
+        // `Ctx` set to "B", when looking up in `B`. We need to set the actual
+        // accessing context (i.e. naming class) to "D" so that access can be
+        // calculated correctly.
+        if (InBaseClass && isa<CXXRecordDecl>(Ctx)) {
+          CXXRecordDecl *RC = nullptr;
+          // Get the enclosing record.
+          for (DeclContext *DC = CurContext; !DC->isFileContext();
+               DC = DC->getParent()) {
+            if ((RC = dyn_cast<CXXRecordDecl>(DC)))
+              break;
+          }
+          if (RC)
+            AccessingCtx = RC;
+        }
+        Accessible = Results.getSema().IsSimplyAccessible(ND, AccessingCtx);
+      }
 
       ResultBuilder::Result Result(ND, Results.getBasePriority(ND), nullptr,
                                    false, Accessible, FixIts);
Index: test/Index/complete-access-checks.cpp
===================================================================
--- test/Index/complete-access-checks.cpp
+++ test/Index/complete-access-checks.cpp
@@ -36,10 +36,10 @@
 
 // CHECK-SUPER-ACCESS: CXXMethod:{ResultType void}{TypedText doSomething}{LeftParen (}{RightParen )} (34)
 // CHECK-SUPER-ACCESS: CXXMethod:{ResultType void}{Informative X::}{TypedText func1}{LeftParen (}{RightParen )} (36)
-// CHECK-SUPER-ACCESS: CXXMethod:{ResultType void}{Informative X::}{TypedText func2}{LeftParen (}{RightParen )} (36) (inaccessible)
+// CHECK-SUPER-ACCESS: CXXMethod:{ResultType void}{Informative X::}{TypedText func2}{LeftParen (}{RightParen )} (36)
 // CHECK-SUPER-ACCESS: CXXMethod:{ResultType void}{Informative X::}{TypedText func3}{LeftParen (}{RightParen )} (36) (inaccessible)
 // CHECK-SUPER-ACCESS: FieldDecl:{ResultType int}{Informative X::}{TypedText member1} (37)
-// CHECK-SUPER-ACCESS: FieldDecl:{ResultType int}{Informative X::}{TypedText member2} (37) (inaccessible)
+// CHECK-SUPER-ACCESS: FieldDecl:{ResultType int}{Informative X::}{TypedText member2} (37)
 // CHECK-SUPER-ACCESS: FieldDecl:{ResultType int}{Informative X::}{TypedText member3} (37) (inaccessible)
 // CHECK-SUPER-ACCESS: CXXMethod:{ResultType Y &}{TypedText operator=}{LeftParen (}{Placeholder const Y &}{RightParen )} (79)
 // CHECK-SUPER-ACCESS: CXXMethod:{ResultType X &}{Text X::}{TypedText operator=}{LeftParen (}{Placeholder const X &}{RightParen )} (81)
@@ -87,3 +87,26 @@
 // CHECK-USING-ACCESSIBLE: ClassDecl:{TypedText Q}{Text ::} (75)
 // CHECK-USING-ACCESSIBLE: CXXDestructor:{ResultType void}{Informative P::}{TypedText ~P}{LeftParen (}{RightParen )} (81)
 // CHECK-USING-ACCESSIBLE: CXXDestructor:{ResultType void}{TypedText ~Q}{LeftParen (}{RightParen )} (79)
+
+class B {
+protected:
+  int member;
+};
+
+class C : private B {};
+
+
+class D : public C {
+ public:
+  void f(::B *b);
+};
+
+void D::f(::B *that) {
+  // RUN: c-index-test -code-completion-at=%s:106:9 %s | FileCheck -check-prefix=CHECK-PRIVATE-SUPER-THIS %s
+  this->;
+// CHECK-PRIVATE-SUPER-THIS: FieldDecl:{ResultType int}{Informative B::}{TypedText member} (37) (inaccessible)
+
+  // RUN: c-index-test -code-completion-at=%s:110:9 %s | FileCheck -check-prefix=CHECK-PRIVATE-SUPER-THAT %s
+  that->;
+// CHECK-PRIVATE-SUPER-THAT: FieldDecl:{ResultType int}{TypedText member} (35) (inaccessible)
+}