Index: include/clang/Sema/Sema.h
===================================================================
--- include/clang/Sema/Sema.h
+++ include/clang/Sema/Sema.h
@@ -7072,6 +7072,23 @@
     DAR_FailedAlreadyDiagnosed
   };
 
+  /// RAII class that is used to determine whether we are deducing the type of
+  /// an auto variable.
+  class DeduceAutoTypeRAII {
+    Sema &SemaRef;
+  public:
+    DeduceAutoTypeRAII(Sema &SemaRef) : SemaRef(SemaRef) {
+      SemaRef.DeduceAutoTypeRAIIs.push_back(this);
+    }
+    ~DeduceAutoTypeRAII() { SemaRef.DeduceAutoTypeRAIIs.pop_back(); }
+  };
+
+  friend DeduceAutoTypeRAII;
+
+  SmallVector<DeduceAutoTypeRAII *, 1> DeduceAutoTypeRAIIs;
+
+  bool deducingAutoType() const { return !DeduceAutoTypeRAIIs.empty(); }
+
   DeduceAutoResult
   DeduceAutoType(TypeSourceInfo *AutoType, Expr *&Initializer, QualType &Result,
                  Optional<unsigned> DependentDeductionDepth = None);
Index: lib/Sema/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp
+++ lib/Sema/SemaExpr.cpp
@@ -14550,6 +14550,10 @@
 }
 
 ExprResult Sema::HandleExprEvaluationContextForTypeof(Expr *E) {
+  ExprResult Result = CheckPlaceholderExpr(E);
+  if (Result.isInvalid())
+    return ExprError();
+  E = Result.get();
   if (!E->getType()->isVariablyModifiedType())
     return E;
   return TransformToPotentiallyEvaluated(E);
Index: lib/Sema/SemaExprCXX.cpp
===================================================================
--- lib/Sema/SemaExprCXX.cpp
+++ lib/Sema/SemaExprCXX.cpp
@@ -6543,6 +6543,11 @@
              ExpressionEvaluationContextRecord::EK_Decltype &&
          "not in a decltype expression");
 
+  ExprResult Result = CheckPlaceholderExpr(E);
+  if (Result.isInvalid())
+    return ExprError();
+  E = Result.get();
+
   // C++11 [expr.call]p11:
   //   If a function call is a prvalue of object type,
   // -- if the function call is either
Index: lib/Sema/SemaExprMember.cpp
===================================================================
--- lib/Sema/SemaExprMember.cpp
+++ lib/Sema/SemaExprMember.cpp
@@ -1712,6 +1712,8 @@
       Base, Base->getType(), OpLoc, IsArrow, SS, TemplateKWLoc,
       FirstQualifierInScope, NameInfo, TemplateArgs, S, &ExtraArgs);
 
+  Res = CheckPlaceholderExpr(Res.get());
+
   if (!Res.isInvalid() && isa<MemberExpr>(Res.get()))
     CheckMemberAccessOfNoDeref(cast<MemberExpr>(Res.get()));
 
Index: lib/Sema/SemaExprObjC.cpp
===================================================================
--- lib/Sema/SemaExprObjC.cpp
+++ lib/Sema/SemaExprObjC.cpp
@@ -3161,7 +3161,7 @@
           Prop->getPropertyAttributes() & ObjCPropertyDecl::OBJC_PR_weak;
         if (!IsWeak && Sel.isUnarySelector())
           IsWeak = ReturnType.getObjCLifetime() & Qualifiers::OCL_Weak;
-        if (IsWeak &&
+        if (IsWeak && !isUnevaluatedContext() &&
             !Diags.isIgnored(diag::warn_arc_repeated_use_of_weak, LBracLoc))
           getCurFunction()->recordUseOfWeak(Result, Prop);
       }
Index: lib/Sema/SemaPseudoObject.cpp
===================================================================
--- lib/Sema/SemaPseudoObject.cpp
+++ lib/Sema/SemaPseudoObject.cpp
@@ -975,7 +975,7 @@
 }
 
 ExprResult ObjCPropertyOpBuilder::complete(Expr *SyntacticForm) {
-  if (isWeakProperty() && !S.isUnevaluatedContext() &&
+  if (isWeakProperty() && !S.isUnevaluatedContext() && !S.deducingAutoType() &&
       !S.Diags.isIgnored(diag::warn_arc_repeated_use_of_weak,
                          SyntacticForm->getBeginLoc()))
     S.getCurFunction()->recordUseOfWeak(SyntacticRefExpr,
Index: lib/Sema/SemaTemplateDeduction.cpp
===================================================================
--- lib/Sema/SemaTemplateDeduction.cpp
+++ lib/Sema/SemaTemplateDeduction.cpp
@@ -4402,6 +4402,8 @@
 Sema::DeduceAutoResult
 Sema::DeduceAutoType(TypeLoc Type, Expr *&Init, QualType &Result,
                      Optional<unsigned> DependentDeductionDepth) {
+  DeduceAutoTypeRAII RAII(*this);
+
   if (Init->getType()->isNonOverloadPlaceholderType()) {
     ExprResult NonPlaceholder = CheckPlaceholderExpr(Init);
     if (NonPlaceholder.isInvalid())
@@ -4429,6 +4431,10 @@
         return DAR_FailedAlreadyDiagnosed;
       }
 
+      ExprResult ER = CheckPlaceholderExpr(Init);
+      if (ER.isInvalid())
+        return DAR_FailedAlreadyDiagnosed;
+      Init = ER.get();
       QualType Deduced = BuildDecltypeType(Init, Init->getBeginLoc(), false);
       if (Deduced.isNull())
         return DAR_FailedAlreadyDiagnosed;
Index: lib/Sema/SemaType.cpp
===================================================================
--- lib/Sema/SemaType.cpp
+++ lib/Sema/SemaType.cpp
@@ -8056,9 +8056,7 @@
 }
 
 QualType Sema::BuildTypeofExprType(Expr *E, SourceLocation Loc) {
-  ExprResult ER = CheckPlaceholderExpr(E);
-  if (ER.isInvalid()) return QualType();
-  E = ER.get();
+  assert(!E->hasPlaceholderType() && "unexpected placeholder");
 
   if (!getLangOpts().CPlusPlus && E->refersToBitField())
     Diag(E->getExprLoc(), diag::err_sizeof_alignof_typeof_bitfield) << 2;
@@ -8143,9 +8141,7 @@
 
 QualType Sema::BuildDecltypeType(Expr *E, SourceLocation Loc,
                                  bool AsUnevaluated) {
-  ExprResult ER = CheckPlaceholderExpr(E);
-  if (ER.isInvalid()) return QualType();
-  E = ER.get();
+  assert(!E->hasPlaceholderType() && "unexpected placeholder");
 
   if (AsUnevaluated && CodeSynthesisContexts.empty() &&
       E->HasSideEffects(Context, false)) {
Index: test/SemaObjC/arc-repeated-weak.mm
===================================================================
--- test/SemaObjC/arc-repeated-weak.mm
+++ test/SemaObjC/arc-repeated-weak.mm
@@ -462,6 +462,13 @@
   NSString * t2 = NSBundle.foo2.prop;
   use(NSBundle.foo2.weakProp); // expected-warning{{weak property 'weakProp' may be accessed multiple times}}
   use(NSBundle2.foo2.weakProp); // expected-note{{also accessed here}}
+  decltype([NSBundle2.foo2 weakProp]) t3;
+  decltype(NSBundle2.foo2.weakProp) t4;
+  __typeof__(NSBundle2.foo2.weakProp) t5;
+}
+
+void testAuto() {
+  auto __weak wp = NSBundle2.foo2.weakProp;
 }
 
 // This used to crash in the constructor of WeakObjectProfileTy when a