Revert r350404

This caused https://bugs.llvm.org/show_bug.cgi?id=40642:
"After 350404, clang drops volatile load"

> Refactor the way we handle diagnosing unused expression results.
>
> Rather than sprinkle calls to DiagnoseUnusedExprResult() around in places
> where we want diagnostics, we now diagnose unused expression statements and
> full expressions in a more generic way when acting on the final expression
> statement. This results in more appropriate diagnostics for [[nodiscard]] where
> we were previously lacking them, such as when the body of a for loop is not a
> compound statement.
>
> This patch fixes PR39837.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_80@353935 91177308-0d34-0410-b5e6-96231b3b80d8

21 files changed, 122 insertions, 196 deletions

diff --git a/include/clang/Parse/Parser.h b/include/clang/Parse/Parser.h
index 438ff0e2ed..46e4431913 100644
--- a/include/clang/Parse/Parser.h
+++ b/include/clang/Parse/Parser.h
@@ -360,11 +360,6 @@ class Parser : public CodeCompletionHandler {
   /// just a regular sub-expression.
   SourceLocation ExprStatementTokLoc;
 
-  /// Tests whether an expression value is discarded based on token lookahead.
-  /// It will return true if the lexer is currently processing the })
-  /// terminating a GNU statement expression and false otherwise.
-  bool isExprValueDiscarded();
-
 public:
   Parser(Preprocessor &PP, Sema &Actions, bool SkipFunctionBodies);
   ~Parser() override;
diff --git a/include/clang/Sema/Sema.h b/include/clang/Sema/Sema.h
index e5b7465820..ced5773f0c 100644
--- a/include/clang/Sema/Sema.h
+++ b/include/clang/Sema/Sema.h
@@ -1369,7 +1369,6 @@ public:
   void PopCompoundScope();
 
   sema::CompoundScopeInfo &getCurCompoundScope() const;
-  bool isCurCompoundStmtAStmtExpr() const;
 
   bool hasAnyUnrecoverableErrorsInThisFunction() const;
 
@@ -3690,17 +3689,16 @@ public:
     return MakeFullExpr(Arg, Arg ? Arg->getExprLoc() : SourceLocation());
   }
   FullExprArg MakeFullExpr(Expr *Arg, SourceLocation CC) {
-    return FullExprArg(
-        ActOnFinishFullExpr(Arg, CC, /*DiscardedValue*/ false).get());
+    return FullExprArg(ActOnFinishFullExpr(Arg, CC).get());
   }
   FullExprArg MakeFullDiscardedValueExpr(Expr *Arg) {
     ExprResult FE =
-        ActOnFinishFullExpr(Arg, Arg ? Arg->getExprLoc() : SourceLocation(),
-                            /*DiscardedValue*/ true);
+      ActOnFinishFullExpr(Arg, Arg ? Arg->getExprLoc() : SourceLocation(),
+                          /*DiscardedValue*/ true);
     return FullExprArg(FE.get());
   }
 
-  StmtResult ActOnExprStmt(ExprResult Arg, bool DiscardedValue = true);
+  StmtResult ActOnExprStmt(ExprResult Arg);
   StmtResult ActOnExprStmtError();
 
   StmtResult ActOnNullStmt(SourceLocation SemiLoc,
@@ -5346,12 +5344,13 @@ public:
   CreateMaterializeTemporaryExpr(QualType T, Expr *Temporary,
                                  bool BoundToLvalueReference);
 
-  ExprResult ActOnFinishFullExpr(Expr *Expr, bool DiscardedValue) {
-    return ActOnFinishFullExpr(
-        Expr, Expr ? Expr->getExprLoc() : SourceLocation(), DiscardedValue);
+  ExprResult ActOnFinishFullExpr(Expr *Expr) {
+    return ActOnFinishFullExpr(Expr, Expr ? Expr->getExprLoc()
+                                          : SourceLocation());
   }
   ExprResult ActOnFinishFullExpr(Expr *Expr, SourceLocation CC,
-                                 bool DiscardedValue, bool IsConstexpr = false);
+                                 bool DiscardedValue = false,
+                                 bool IsConstexpr = false);
   StmtResult ActOnFinishFullStmt(Stmt *Stmt);
 
   // Marks SS invalid if it represents an incomplete type.
diff --git a/lib/Parse/ParseObjc.cpp b/lib/Parse/ParseObjc.cpp
index bd55f71793..c8d7bda3d6 100644
--- a/lib/Parse/ParseObjc.cpp
+++ b/lib/Parse/ParseObjc.cpp
@@ -2741,7 +2741,7 @@ StmtResult Parser::ParseObjCAtStatement(SourceLocation AtLoc) {
 
   // Otherwise, eat the semicolon.
   ExpectAndConsumeSemi(diag::err_expected_semi_after_expr);
-  return Actions.ActOnExprStmt(Res, isExprValueDiscarded());
+  return Actions.ActOnExprStmt(Res);
 }
 
 ExprResult Parser::ParseObjCAtExpression(SourceLocation AtLoc) {
diff --git a/lib/Parse/ParseOpenMP.cpp b/lib/Parse/ParseOpenMP.cpp
index dd2a8aae9f..17c3fa3cf2 100644
--- a/lib/Parse/ParseOpenMP.cpp
+++ b/lib/Parse/ParseOpenMP.cpp
@@ -314,7 +314,7 @@ Parser::ParseOpenMPDeclareReductionDirective(AccessSpecifier AS) {
     Actions.ActOnOpenMPDeclareReductionCombinerStart(getCurScope(), D);
     ExprResult CombinerResult =
         Actions.ActOnFinishFullExpr(ParseAssignmentExpression().get(),
-                                    D->getLocation(), /*DiscardedValue*/ false);
+                                    D->getLocation(), /*DiscardedValue=*/true);
     Actions.ActOnOpenMPDeclareReductionCombinerEnd(D, CombinerResult.get());
 
     if (CombinerResult.isInvalid() && Tok.isNot(tok::r_paren) &&
@@ -356,7 +356,7 @@ Parser::ParseOpenMPDeclareReductionDirective(AccessSpecifier AS) {
           if (Actions.getLangOpts().CPlusPlus) {
             InitializerResult = Actions.ActOnFinishFullExpr(
                 ParseAssignmentExpression().get(), D->getLocation(),
-                /*DiscardedValue*/ false);
+                /*DiscardedValue=*/true);
           } else {
             ConsumeToken();
             ParseOpenMPReductionInitializerForDecl(OmpPrivParm);
@@ -364,7 +364,7 @@ Parser::ParseOpenMPDeclareReductionDirective(AccessSpecifier AS) {
         } else {
           InitializerResult = Actions.ActOnFinishFullExpr(
               ParseAssignmentExpression().get(), D->getLocation(),
-              /*DiscardedValue*/ false);
+              /*DiscardedValue=*/true);
         }
         Actions.ActOnOpenMPDeclareReductionInitializerEnd(
             D, InitializerResult.get(), OmpPrivParm);
@@ -1455,7 +1455,7 @@ ExprResult Parser::ParseOpenMPParensExpr(StringRef ClauseName,
   ExprResult LHS(ParseCastExpression(
       /*isUnaryExpression=*/false, /*isAddressOfOperand=*/false, NotTypeCast));
   ExprResult Val(ParseRHSOfBinaryExpression(LHS, prec::Conditional));
-  Val = Actions.ActOnFinishFullExpr(Val.get(), ELoc, /*DiscardedValue*/ false);
+  Val = Actions.ActOnFinishFullExpr(Val.get(), ELoc);
 
   // Parse ')'.
   RLoc = Tok.getLocation();
@@ -1711,8 +1711,7 @@ OMPClause *Parser::ParseOpenMPSingleExprWithArgClause(OpenMPClauseKind Kind,
     SourceLocation ELoc = Tok.getLocation();
     ExprResult LHS(ParseCastExpression(false, false, NotTypeCast));
     Val = ParseRHSOfBinaryExpression(LHS, prec::Conditional);
-    Val =
-        Actions.ActOnFinishFullExpr(Val.get(), ELoc, /*DiscardedValue*/ false);
+    Val = Actions.ActOnFinishFullExpr(Val.get(), ELoc);
   }
 
   // Parse ')'.
@@ -1997,8 +1996,7 @@ bool Parser::ParseOpenMPVarList(OpenMPDirectiveKind DKind,
     Data.ColonLoc = Tok.getLocation();
     SourceLocation ELoc = ConsumeToken();
     ExprResult Tail = ParseAssignmentExpression();
-    Tail =
-        Actions.ActOnFinishFullExpr(Tail.get(), ELoc, /*DiscardedValue*/ false);
+    Tail = Actions.ActOnFinishFullExpr(Tail.get(), ELoc);
     if (Tail.isUsable())
       Data.TailExpr = Tail.get();
     else
diff --git a/lib/Parse/ParseStmt.cpp b/lib/Parse/ParseStmt.cpp
index 2974e6a245..313793c3e8 100644
--- a/lib/Parse/ParseStmt.cpp
+++ b/lib/Parse/ParseStmt.cpp
@@ -439,7 +439,7 @@ StmtResult Parser::ParseExprStatement() {
 
   // Otherwise, eat the semicolon.
   ExpectAndConsumeSemi(diag::err_expected_semi_after_expr);
-  return Actions.ActOnExprStmt(Expr, isExprValueDiscarded());
+  return Actions.ActOnExprStmt(Expr);
 }
 
 /// ParseSEHTryBlockCommon
@@ -958,16 +958,6 @@ bool Parser::ConsumeNullStmt(StmtVector &Stmts) {
   return true;
 }
 
-bool Parser::isExprValueDiscarded() {
-  if (Actions.isCurCompoundStmtAStmtExpr()) {
-    // Look to see if the next two tokens close the statement expression;
-    // if so, this expression statement is the last statement in a
-    // statment expression.
-    return Tok.isNot(tok::r_brace) || NextToken().isNot(tok::r_paren);
-  }
-  return true;
-}
-
 /// ParseCompoundStatementBody - Parse a sequence of statements and invoke the
 /// ActOnCompoundStmt action.  This expects the '{' to be the current token, and
 /// consume the '}' at the end of the block.  It does not manipulate the scope
@@ -1072,7 +1062,7 @@ StmtResult Parser::ParseCompoundStatementBody(bool isStmtExpr) {
         // Eat the semicolon at the end of stmt and convert the expr into a
         // statement.
         ExpectAndConsumeSemi(diag::err_expected_semi_after_expr);
-        R = Actions.ActOnExprStmt(Res, isExprValueDiscarded());
+        R = Actions.ActOnExprStmt(Res);
       }
     }
 
@@ -1708,16 +1698,8 @@ StmtResult Parser::ParseForStatement(SourceLocation *TrailingElseLoc) {
     if (!Value.isInvalid()) {
       if (ForEach)
         FirstPart = Actions.ActOnForEachLValueExpr(Value.get());
-      else {
-        // We already know this is not an init-statement within a for loop, so
-        // if we are parsing a C++11 range-based for loop, we should treat this
-        // expression statement as being a discarded value expression because
-        // we will err below. This way we do not warn on an unused expression
-        // that was an error in the first place, like with: for (expr : expr);
-        bool IsRangeBasedFor =
-            getLangOpts().CPlusPlus11 && !ForEach && Tok.is(tok::colon);
-        FirstPart = Actions.ActOnExprStmt(Value, !IsRangeBasedFor);
-      }
+      else
+        FirstPart = Actions.ActOnExprStmt(Value);
     }
 
     if (Tok.is(tok::semi)) {
diff --git a/lib/Sema/SemaCoroutine.cpp b/lib/Sema/SemaCoroutine.cpp
index 181efa6d3d..e282bb62f0 100644
--- a/lib/Sema/SemaCoroutine.cpp
+++ b/lib/Sema/SemaCoroutine.cpp
@@ -646,7 +646,7 @@ bool Sema::ActOnCoroutineBodyStart(Scope *SC, SourceLocation KWLoc,
       return StmtError();
     Suspend = BuildResolvedCoawaitExpr(Loc, Suspend.get(),
                                        /*IsImplicit*/ true);
-    Suspend = ActOnFinishFullExpr(Suspend.get(), /*DiscardedValue*/ false);
+    Suspend = ActOnFinishFullExpr(Suspend.get());
     if (Suspend.isInvalid()) {
       Diag(Loc, diag::note_coroutine_promise_suspend_implicitly_required)
           << ((Name == "initial_suspend") ? 0 : 1);
@@ -867,7 +867,7 @@ StmtResult Sema::BuildCoreturnStmt(SourceLocation Loc, Expr *E,
   if (PC.isInvalid())
     return StmtError();
 
-  Expr *PCE = ActOnFinishFullExpr(PC.get(), /*DiscardedValue*/ false).get();
+  Expr *PCE = ActOnFinishFullExpr(PC.get()).get();
 
   Stmt *Res = new (Context) CoreturnStmt(Loc, E, PCE, IsImplicit);
   return Res;
@@ -1236,7 +1236,7 @@ bool CoroutineStmtBuilder::makeNewAndDeleteExpr() {
 
   ExprResult NewExpr =
       S.ActOnCallExpr(S.getCurScope(), NewRef.get(), Loc, NewArgs, Loc);
-  NewExpr = S.ActOnFinishFullExpr(NewExpr.get(), /*DiscardedValue*/ false);
+  NewExpr = S.ActOnFinishFullExpr(NewExpr.get());
   if (NewExpr.isInvalid())
     return false;
 
@@ -1262,8 +1262,7 @@ bool CoroutineStmtBuilder::makeNewAndDeleteExpr() {
 
   ExprResult DeleteExpr =
       S.ActOnCallExpr(S.getCurScope(), DeleteRef.get(), Loc, DeleteArgs, Loc);
-  DeleteExpr =
-      S.ActOnFinishFullExpr(DeleteExpr.get(), /*DiscardedValue*/ false);
+  DeleteExpr = S.ActOnFinishFullExpr(DeleteExpr.get());
   if (DeleteExpr.isInvalid())
     return false;
 
@@ -1348,8 +1347,7 @@ bool CoroutineStmtBuilder::makeOnException() {
 
   ExprResult UnhandledException = buildPromiseCall(S, Fn.CoroutinePromise, Loc,
                                                    "unhandled_exception", None);
-  UnhandledException = S.ActOnFinishFullExpr(UnhandledException.get(), Loc,
-                                             /*DiscardedValue*/ false);
+  UnhandledException = S.ActOnFinishFullExpr(UnhandledException.get(), Loc);
   if (UnhandledException.isInvalid())
     return false;
 
@@ -1402,8 +1400,7 @@ bool CoroutineStmtBuilder::makeGroDeclAndReturnStmt() {
          "get_return_object type must no longer be dependent");
 
   if (FnRetType->isVoidType()) {
-    ExprResult Res =
-        S.ActOnFinishFullExpr(this->ReturnValue, Loc, /*DiscardedValue*/ false);
+    ExprResult Res = S.ActOnFinishFullExpr(this->ReturnValue, Loc);
     if (Res.isInvalid())
       return false;
 
@@ -1435,7 +1432,7 @@ bool CoroutineStmtBuilder::makeGroDeclAndReturnStmt() {
   if (Res.isInvalid())
     return false;
 
-  Res = S.ActOnFinishFullExpr(Res.get(), /*DiscardedValue*/ false);
+  Res = S.ActOnFinishFullExpr(Res.get());
   if (Res.isInvalid())
     return false;
 
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 23c99d45a7..7ddf2e88b7 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -11200,9 +11200,9 @@ void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init, bool DirectInit) {
   //   struct T { S a, b; } t = { Temp(), Temp() }
   //
   // we should destroy the first Temp before constructing the second.
-  ExprResult Result =
-      ActOnFinishFullExpr(Init, VDecl->getLocation(),
-                          /*DiscardedValue*/ false, VDecl->isConstexpr());
+  ExprResult Result = ActOnFinishFullExpr(Init, VDecl->getLocation(),
+                                          false,
+                                          VDecl->isConstexpr());
   if (Result.isInvalid()) {
     VDecl->setInvalidDecl();
     return;
diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index 8b3556f715..950a63aa45 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -1205,7 +1205,7 @@ static bool checkTupleLikeDecomposition(Sema &S,
     E = Seq.Perform(S, Entity, Kind, Init);
     if (E.isInvalid())
       return true;
-    E = S.ActOnFinishFullExpr(E.get(), Loc, /*DiscardedValue*/ false);
+    E = S.ActOnFinishFullExpr(E.get(), Loc);
     if (E.isInvalid())
       return true;
     RefVD->setInit(E.get());
@@ -3686,7 +3686,7 @@ void Sema::ActOnFinishCXXInClassMemberInitializer(Decl *D,
   // C++11 [class.base.init]p7:
   //   The initialization of each base and member constitutes a
   //   full-expression.
-  Init = ActOnFinishFullExpr(Init.get(), InitLoc, /*DiscardedValue*/ false);
+  Init = ActOnFinishFullExpr(Init.get(), InitLoc);
   if (Init.isInvalid()) {
     FD->setInvalidDecl();
     return;
@@ -4044,8 +4044,7 @@ Sema::BuildMemberInitializer(ValueDecl *Member, Expr *Init,
     // C++11 [class.base.init]p7:
     //   The initialization of each base and member constitutes a
     //   full-expression.
-    MemberInit = ActOnFinishFullExpr(MemberInit.get(), InitRange.getBegin(),
-                                     /*DiscardedValue*/ false);
+    MemberInit = ActOnFinishFullExpr(MemberInit.get(), InitRange.getBegin());
     if (MemberInit.isInvalid())
       return true;
 
@@ -4100,8 +4099,8 @@ Sema::BuildDelegatingInitializer(TypeSourceInfo *TInfo, Expr *Init,
   // C++11 [class.base.init]p7:
   //   The initialization of each base and member constitutes a
   //   full-expression.
-  DelegationInit = ActOnFinishFullExpr(
-      DelegationInit.get(), InitRange.getBegin(), /*DiscardedValue*/ false);
+  DelegationInit = ActOnFinishFullExpr(DelegationInit.get(),
+                                       InitRange.getBegin());
   if (DelegationInit.isInvalid())
     return true;
 
@@ -4230,8 +4229,7 @@ Sema::BuildBaseInitializer(QualType BaseType, TypeSourceInfo *BaseTInfo,
   // C++11 [class.base.init]p7:
   //   The initialization of each base and member constitutes a
   //   full-expression.
-  BaseInit = ActOnFinishFullExpr(BaseInit.get(), InitRange.getBegin(),
-                                 /*DiscardedValue*/ false);
+  BaseInit = ActOnFinishFullExpr(BaseInit.get(), InitRange.getBegin());
   if (BaseInit.isInvalid())
     return true;
 
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 2bcd47abe3..db0c62630a 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -4723,9 +4723,8 @@ bool Sema::CheckCXXDefaultArgExpr(SourceLocation CallLoc, FunctionDecl *FD,
     if (Result.isInvalid())
       return true;
 
-    Result =
-        ActOnFinishFullExpr(Result.getAs<Expr>(), Param->getOuterLocStart(),
-                            /*DiscardedValue*/ false);
+    Result = ActOnFinishFullExpr(Result.getAs<Expr>(),
+                                 Param->getOuterLocStart());
     if (Result.isInvalid())
       return true;
 
diff --git a/lib/Sema/SemaExprCXX.cpp b/lib/Sema/SemaExprCXX.cpp
index 8c89a3cee3..cce7a21654 100644
--- a/lib/Sema/SemaExprCXX.cpp
+++ b/lib/Sema/SemaExprCXX.cpp
@@ -7815,8 +7815,6 @@ ExprResult Sema::ActOnFinishFullExpr(Expr *FE, SourceLocation CC,
     FullExpr = IgnoredValueConversions(FullExpr.get());
     if (FullExpr.isInvalid())
       return ExprError();
-
-    DiagnoseUnusedExprResult(FullExpr.get());
   }
 
   FullExpr = CorrectDelayedTyposInExpr(FullExpr.get());
diff --git a/lib/Sema/SemaLambda.cpp b/lib/Sema/SemaLambda.cpp
index af233b96d6..4e002a853d 100644
--- a/lib/Sema/SemaLambda.cpp
+++ b/lib/Sema/SemaLambda.cpp
@@ -1724,7 +1724,7 @@ ExprResult Sema::BuildBlockForLambdaConversion(SourceLocation CurrentLocation,
                                                  /*NRVO=*/false),
       CurrentLocation, Src);
   if (!Init.isInvalid())
-    Init = ActOnFinishFullExpr(Init.get(), /*DiscardedValue*/ false);
+    Init = ActOnFinishFullExpr(Init.get());
 
   if (Init.isInvalid())
     return ExprError();
diff --git a/lib/Sema/SemaOpenMP.cpp b/lib/Sema/SemaOpenMP.cpp
index 36048a38b9..aedec746af 100644
--- a/lib/Sema/SemaOpenMP.cpp
+++ b/lib/Sema/SemaOpenMP.cpp
@@ -5367,7 +5367,7 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
         LastIteration.get(), UB.get());
     EUB = SemaRef.BuildBinOp(CurScope, InitLoc, BO_Assign, UB.get(),
                              CondOp.get());
-    EUB = SemaRef.ActOnFinishFullExpr(EUB.get(), /*DiscardedValue*/ false);
+    EUB = SemaRef.ActOnFinishFullExpr(EUB.get());
 
     // If we have a combined directive that combines 'distribute', 'for' or
     // 'simd' we need to be able to access the bounds of the schedule of the
@@ -5396,8 +5396,7 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
                                      LastIteration.get(), CombUB.get());
       CombEUB = SemaRef.BuildBinOp(CurScope, InitLoc, BO_Assign, CombUB.get(),
                                    CombCondOp.get());
-      CombEUB =
-          SemaRef.ActOnFinishFullExpr(CombEUB.get(), /*DiscardedValue*/ false);
+      CombEUB = SemaRef.ActOnFinishFullExpr(CombEUB.get());
 
       const CapturedDecl *CD = cast<CapturedStmt>(AStmt)->getCapturedDecl();
       // We expect to have at least 2 more parameters than the 'parallel'
@@ -5431,7 +5430,7 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
             ? LB.get()
             : SemaRef.ActOnIntegerConstant(SourceLocation(), 0).get();
     Init = SemaRef.BuildBinOp(CurScope, InitLoc, BO_Assign, IV.get(), RHS);
-    Init = SemaRef.ActOnFinishFullExpr(Init.get(), /*DiscardedValue*/ false);
+    Init = SemaRef.ActOnFinishFullExpr(Init.get());
 
     if (isOpenMPLoopBoundSharingDirective(DKind)) {
       Expr *CombRHS =
@@ -5442,8 +5441,7 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
               : SemaRef.ActOnIntegerConstant(SourceLocation(), 0).get();
       CombInit =
           SemaRef.BuildBinOp(CurScope, InitLoc, BO_Assign, IV.get(), CombRHS);
-      CombInit =
-          SemaRef.ActOnFinishFullExpr(CombInit.get(), /*DiscardedValue*/ false);
+      CombInit = SemaRef.ActOnFinishFullExpr(CombInit.get());
     }
   }
 
@@ -5475,7 +5473,7 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
   if (!Inc.isUsable())
     return 0;
   Inc = SemaRef.BuildBinOp(CurScope, IncLoc, BO_Assign, IV.get(), Inc.get());
-  Inc = SemaRef.ActOnFinishFullExpr(Inc.get(), /*DiscardedValue*/ false);
+  Inc = SemaRef.ActOnFinishFullExpr(Inc.get());
   if (!Inc.isUsable())
     return 0;
 
@@ -5493,8 +5491,7 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
     // LB = LB + ST
     NextLB =
         SemaRef.BuildBinOp(CurScope, IncLoc, BO_Assign, LB.get(), NextLB.get());
-    NextLB =
-        SemaRef.ActOnFinishFullExpr(NextLB.get(), /*DiscardedValue*/ false);
+    NextLB = SemaRef.ActOnFinishFullExpr(NextLB.get());
     if (!NextLB.isUsable())
       return 0;
     // UB + ST
@@ -5504,8 +5501,7 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
     // UB = UB + ST
     NextUB =
         SemaRef.BuildBinOp(CurScope, IncLoc, BO_Assign, UB.get(), NextUB.get());
-    NextUB =
-        SemaRef.ActOnFinishFullExpr(NextUB.get(), /*DiscardedValue*/ false);
+    NextUB = SemaRef.ActOnFinishFullExpr(NextUB.get());
     if (!NextUB.isUsable())
       return 0;
     if (isOpenMPLoopBoundSharingDirective(DKind)) {
@@ -5516,8 +5512,7 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
       // LB = LB + ST
       CombNextLB = SemaRef.BuildBinOp(CurScope, IncLoc, BO_Assign, CombLB.get(),
                                       CombNextLB.get());
-      CombNextLB = SemaRef.ActOnFinishFullExpr(CombNextLB.get(),
-                                               /*DiscardedValue*/ false);
+      CombNextLB = SemaRef.ActOnFinishFullExpr(CombNextLB.get());
       if (!CombNextLB.isUsable())
         return 0;
       // UB + ST
@@ -5528,8 +5523,7 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
       // UB = UB + ST
       CombNextUB = SemaRef.BuildBinOp(CurScope, IncLoc, BO_Assign, CombUB.get(),
                                       CombNextUB.get());
-      CombNextUB = SemaRef.ActOnFinishFullExpr(CombNextUB.get(),
-                                               /*DiscardedValue*/ false);
+      CombNextUB = SemaRef.ActOnFinishFullExpr(CombNextUB.get());
       if (!CombNextUB.isUsable())
         return 0;
     }
@@ -5550,8 +5544,7 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
     assert(DistInc.isUsable() && "distribute inc expr was not built");
     DistInc = SemaRef.BuildBinOp(CurScope, DistIncLoc, BO_Assign, IV.get(),
                                  DistInc.get());
-    DistInc =
-        SemaRef.ActOnFinishFullExpr(DistInc.get(), /*DiscardedValue*/ false);
+    DistInc = SemaRef.ActOnFinishFullExpr(DistInc.get());
     assert(DistInc.isUsable() && "distribute inc expr was not built");
 
     // Build expression: UB = min(UB, prevUB) for #for in composite or combined
@@ -5563,8 +5556,7 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
         DistEUBLoc, DistEUBLoc, IsUBGreater.get(), PrevUB.get(), UB.get());
     PrevEUB = SemaRef.BuildBinOp(CurScope, DistIncLoc, BO_Assign, UB.get(),
                                  CondOp.get());
-    PrevEUB =
-        SemaRef.ActOnFinishFullExpr(PrevEUB.get(), /*DiscardedValue*/ false);
+    PrevEUB = SemaRef.ActOnFinishFullExpr(PrevEUB.get());
 
     // Build IV <= PrevUB to be used in parallel for is in combination with
     // a distribute directive with schedule(static, 1)
@@ -5680,10 +5672,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
   Built.IterationVarRef = IV.get();
   Built.LastIteration = LastIteration.get();
   Built.NumIterations = NumIterations.get();
-  Built.CalcLastIteration = SemaRef
-                                .ActOnFinishFullExpr(CalcLastIteration.get(),
-                                                     /*DiscardedValue*/ false)
-                                .get();
+  Built.CalcLastIteration =
+      SemaRef.ActOnFinishFullExpr(CalcLastIteration.get()).get();
   Built.PreCond = PreCond.get();
   Built.PreInits = buildPreInits(C, Captures);
   Built.Cond = Cond.get();
@@ -10358,8 +10348,8 @@ OMPClause *Sema::ActOnOpenMPLastprivateClause(ArrayRef<Expr *> VarList,
                                          PseudoDstExpr, PseudoSrcExpr);
     if (AssignmentOp.isInvalid())
       continue;
-    AssignmentOp =
-        ActOnFinishFullExpr(AssignmentOp.get(), ELoc, /*DiscardedValue*/ false);
+    AssignmentOp = ActOnFinishFullExpr(AssignmentOp.get(), ELoc,
+                                       /*DiscardedValue=*/true);
     if (AssignmentOp.isInvalid())
       continue;
 
@@ -11357,8 +11347,7 @@ static bool actOnOMPReductionKindClause(
                            BO_Assign, LHSDRE, ConditionalOp);
         }
         if (ReductionOp.isUsable())
-          ReductionOp = S.ActOnFinishFullExpr(ReductionOp.get(),
-                                              /*DiscardedValue*/ false);
+          ReductionOp = S.ActOnFinishFullExpr(ReductionOp.get());
       }
       if (!ReductionOp.isUsable())
         continue;
@@ -11688,7 +11677,7 @@ OMPClause *Sema::ActOnOpenMPLinearClause(
         buildDeclRefExpr(*this, SaveVar, StepExpr->getType(), StepLoc);
     ExprResult CalcStep =
         BuildBinOp(CurScope, StepLoc, BO_Assign, SaveRef.get(), StepExpr);
-    CalcStep = ActOnFinishFullExpr(CalcStep.get(), /*DiscardedValue*/ false);
+    CalcStep = ActOnFinishFullExpr(CalcStep.get());
 
     // Warn about zero linear step (it would be probably better specified as
     // making corresponding variables 'const').
@@ -11776,7 +11765,7 @@ static bool FinishOpenMPLinearClause(OMPLinearClause &Clause, DeclRefExpr *IV,
     else
       Update = *CurPrivate;
     Update = SemaRef.ActOnFinishFullExpr(Update.get(), DE->getBeginLoc(),
-                                         /*DiscardedValue*/ false);
+                                         /*DiscardedValue=*/true);
 
     // Build final: Var = InitExpr + NumIterations * Step
     ExprResult Final;
@@ -11787,7 +11776,7 @@ static bool FinishOpenMPLinearClause(OMPLinearClause &Clause, DeclRefExpr *IV,
     else
       Final = *CurPrivate;
     Final = SemaRef.ActOnFinishFullExpr(Final.get(), DE->getBeginLoc(),
-                                        /*DiscardedValue*/ false);
+                                        /*DiscardedValue=*/true);
 
     if (!Update.isUsable() || !Final.isUsable()) {
       Updates.push_back(nullptr);
@@ -11955,7 +11944,7 @@ OMPClause *Sema::ActOnOpenMPCopyinClause(ArrayRef<Expr *> VarList,
     if (AssignmentOp.isInvalid())
       continue;
     AssignmentOp = ActOnFinishFullExpr(AssignmentOp.get(), DE->getExprLoc(),
-                                       /*DiscardedValue*/ false);
+                                       /*DiscardedValue=*/true);
     if (AssignmentOp.isInvalid())
       continue;
 
@@ -12063,8 +12052,8 @@ OMPClause *Sema::ActOnOpenMPCopyprivateClause(ArrayRef<Expr *> VarList,
         DSAStack->getCurScope(), ELoc, BO_Assign, PseudoDstExpr, PseudoSrcExpr);
     if (AssignmentOp.isInvalid())
       continue;
-    AssignmentOp =
-        ActOnFinishFullExpr(AssignmentOp.get(), ELoc, /*DiscardedValue*/ false);
+    AssignmentOp = ActOnFinishFullExpr(AssignmentOp.get(), ELoc,
+                                       /*DiscardedValue=*/true);
     if (AssignmentOp.isInvalid())
       continue;
 
diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index 9e30c9a396..dacf8d0cf4 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -42,11 +42,12 @@
 using namespace clang;
 using namespace sema;
 
-StmtResult Sema::ActOnExprStmt(ExprResult FE, bool DiscardedValue) {
+StmtResult Sema::ActOnExprStmt(ExprResult FE) {
   if (FE.isInvalid())
     return StmtError();
 
-  FE = ActOnFinishFullExpr(FE.get(), FE.get()->getExprLoc(), DiscardedValue);
+  FE = ActOnFinishFullExpr(FE.get(), FE.get()->getExprLoc(),
+                           /*DiscardedValue*/ true);
   if (FE.isInvalid())
     return StmtError();
 
@@ -347,10 +348,6 @@ sema::CompoundScopeInfo &Sema::getCurCompoundScope() const {
   return getCurFunction()->CompoundScopes.back();
 }
 
-bool Sema::isCurCompoundStmtAStmtExpr() const {
-  return getCurCompoundScope().IsStmtExpr;
-}
-
 StmtResult Sema::ActOnCompoundStmt(SourceLocation L, SourceLocation R,
                                    ArrayRef<Stmt *> Elts, bool isStmtExpr) {
   const unsigned NumElts = Elts.size();
@@ -373,6 +370,14 @@ StmtResult Sema::ActOnCompoundStmt(SourceLocation L, SourceLocation R,
       Diag(D->getLocation(), diag::ext_mixed_decls_code);
     }
   }
+  // Warn about unused expressions in statements.
+  for (unsigned i = 0; i != NumElts; ++i) {
+    // Ignore statements that are last in a statement expression.
+    if (isStmtExpr && i == NumElts - 1)
+      continue;
+
+    DiagnoseUnusedExprResult(Elts[i]);
+  }
 
   // Check for suspicious empty body (null statement) in `for' and `while'
   // statements.  Don't do anything for template instantiations, this just adds
@@ -464,12 +469,15 @@ Sema::ActOnCaseStmt(SourceLocation CaseLoc, ExprResult LHSVal,
 
 /// ActOnCaseStmtBody - This installs a statement as the body of a case.
 void Sema::ActOnCaseStmtBody(Stmt *S, Stmt *SubStmt) {
+  DiagnoseUnusedExprResult(SubStmt);
   cast<CaseStmt>(S)->setSubStmt(SubStmt);
 }
 
 StmtResult
 Sema::ActOnDefaultStmt(SourceLocation DefaultLoc, SourceLocation ColonLoc,
                        Stmt *SubStmt, Scope *CurScope) {
+  DiagnoseUnusedExprResult(SubStmt);
+
   if (getCurFunction()->SwitchStack.empty()) {
     Diag(DefaultLoc, diag::err_default_not_in_switch);
     return SubStmt;
@@ -563,6 +571,9 @@ StmtResult Sema::BuildIfStmt(SourceLocation IfLoc, bool IsConstexpr,
   if (IsConstexpr || isa<ObjCAvailabilityCheckExpr>(Cond.get().second))
     setFunctionHasBranchProtectedScope();
 
+  DiagnoseUnusedExprResult(thenStmt);
+  DiagnoseUnusedExprResult(elseStmt);
+
   return IfStmt::Create(Context, IfLoc, IsConstexpr, InitStmt, Cond.get().first,
                         Cond.get().second, thenStmt, ElseLoc, elseStmt);
 }
@@ -1290,6 +1301,8 @@ StmtResult Sema::ActOnWhileStmt(SourceLocation WhileLoc, ConditionResult Cond,
       !Diags.isIgnored(diag::warn_comma_operator, CondVal.second->getExprLoc()))
     CommaVisitor(*this).Visit(CondVal.second);
 
+  DiagnoseUnusedExprResult(Body);
+
   if (isa<NullStmt>(Body))
     getCurCompoundScope().setHasEmptyLoopBodies();
 
@@ -1309,7 +1322,7 @@ Sema::ActOnDoStmt(SourceLocation DoLoc, Stmt *Body,
     return StmtError();
   Cond = CondResult.get();
 
-  CondResult = ActOnFinishFullExpr(Cond, DoLoc, /*DiscardedValue*/ false);
+  CondResult = ActOnFinishFullExpr(Cond, DoLoc);
   if (CondResult.isInvalid())
     return StmtError();
   Cond = CondResult.get();
@@ -1319,6 +1332,8 @@ Sema::ActOnDoStmt(SourceLocation DoLoc, Stmt *Body,
       !Diags.isIgnored(diag::warn_comma_operator, Cond->getExprLoc()))
     CommaVisitor(*this).Visit(Cond);
 
+  DiagnoseUnusedExprResult(Body);
+
   return new (Context) DoStmt(Body, Cond, DoLoc, WhileLoc, CondRParen);
 }
 
@@ -1763,6 +1778,11 @@ StmtResult Sema::ActOnForStmt(SourceLocation ForLoc, SourceLocation LParenLoc,
     CommaVisitor(*this).Visit(Second.get().second);
 
   Expr *Third  = third.release().getAs<Expr>();
+
+  DiagnoseUnusedExprResult(First);
+  DiagnoseUnusedExprResult(Third);
+  DiagnoseUnusedExprResult(Body);
+
   if (isa<NullStmt>(Body))
     getCurCompoundScope().setHasEmptyLoopBodies();
 
@@ -1782,7 +1802,7 @@ StmtResult Sema::ActOnForEachLValueExpr(Expr *E) {
   if (result.isInvalid()) return StmtError();
   E = result.get();
 
-  ExprResult FullExpr = ActOnFinishFullExpr(E, /*DiscardedValue*/ false);
+  ExprResult FullExpr = ActOnFinishFullExpr(E);
   if (FullExpr.isInvalid())
     return StmtError();
   return StmtResult(static_cast<Stmt*>(FullExpr.get()));
@@ -1936,8 +1956,7 @@ Sema::ActOnObjCForCollectionStmt(SourceLocation ForLoc,
   if (CollectionExprResult.isInvalid())
     return StmtError();
 
-  CollectionExprResult =
-      ActOnFinishFullExpr(CollectionExprResult.get(), /*DiscardedValue*/ false);
+  CollectionExprResult = ActOnFinishFullExpr(CollectionExprResult.get());
   if (CollectionExprResult.isInvalid())
     return StmtError();
 
@@ -2574,8 +2593,7 @@ StmtResult Sema::BuildCXXForRangeStmt(SourceLocation ForLoc,
     if (!NotEqExpr.isInvalid())
       NotEqExpr = CheckBooleanCondition(ColonLoc, NotEqExpr.get());
     if (!NotEqExpr.isInvalid())
-      NotEqExpr =
-          ActOnFinishFullExpr(NotEqExpr.get(), /*DiscardedValue*/ false);
+      NotEqExpr = ActOnFinishFullExpr(NotEqExpr.get());
     if (NotEqExpr.isInvalid()) {
       Diag(RangeLoc, diag::note_for_range_invalid_iterator)
         << RangeLoc << 0 << BeginRangeRef.get()->getType();
@@ -2598,7 +2616,7 @@ StmtResult Sema::BuildCXXForRangeStmt(SourceLocation ForLoc,
       // co_await during the initial parse.
       IncrExpr = ActOnCoawaitExpr(S, CoawaitLoc, IncrExpr.get());
     if (!IncrExpr.isInvalid())
-      IncrExpr = ActOnFinishFullExpr(IncrExpr.get(), /*DiscardedValue*/ false);
+      IncrExpr = ActOnFinishFullExpr(IncrExpr.get());
     if (IncrExpr.isInvalid()) {
       Diag(RangeLoc, diag::note_for_range_invalid_iterator)
         << RangeLoc << 2 << BeginRangeRef.get()->getType() ;
@@ -2853,7 +2871,7 @@ Sema::ActOnIndirectGotoStmt(SourceLocation GotoLoc, SourceLocation StarLoc,
       return StmtError();
   }
 
-  ExprResult ExprRes = ActOnFinishFullExpr(E, /*DiscardedValue*/ false);
+  ExprResult ExprRes = ActOnFinishFullExpr(E);
   if (ExprRes.isInvalid())
     return StmtError();
   E = ExprRes.get();
@@ -3203,8 +3221,7 @@ Sema::ActOnCapScopeReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
           ExpressionEvaluationContext::DiscardedStatement &&
       (HasDeducedReturnType || CurCap->HasImplicitReturnType)) {
     if (RetValExp) {
-      ExprResult ER =
-          ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/ false);
+      ExprResult ER = ActOnFinishFullExpr(RetValExp, ReturnLoc);
       if (ER.isInvalid())
         return StmtError();
       RetValExp = ER.get();
@@ -3331,8 +3348,7 @@ Sema::ActOnCapScopeReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
   }
 
   if (RetValExp) {
-    ExprResult ER =
-        ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/ false);
+    ExprResult ER = ActOnFinishFullExpr(RetValExp, ReturnLoc);
     if (ER.isInvalid())
       return StmtError();
     RetValExp = ER.get();
@@ -3562,8 +3578,7 @@ StmtResult Sema::BuildReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
           ExpressionEvaluationContext::DiscardedStatement &&
       FnRetType->getContainedAutoType()) {
     if (RetValExp) {
-      ExprResult ER =
-          ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/ false);
+      ExprResult ER = ActOnFinishFullExpr(RetValExp, ReturnLoc);
       if (ER.isInvalid())
         return StmtError();
       RetValExp = ER.get();
@@ -3657,8 +3672,7 @@ StmtResult Sema::BuildReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
       }
 
       if (RetValExp) {
-        ExprResult ER =
-            ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/ false);
+        ExprResult ER = ActOnFinishFullExpr(RetValExp, ReturnLoc);
         if (ER.isInvalid())
           return StmtError();
         RetValExp = ER.get();
@@ -3737,8 +3751,7 @@ StmtResult Sema::BuildReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
     }
 
     if (RetValExp) {
-      ExprResult ER =
-          ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/ false);
+      ExprResult ER = ActOnFinishFullExpr(RetValExp, ReturnLoc);
       if (ER.isInvalid())
         return StmtError();
       RetValExp = ER.get();
@@ -3791,7 +3804,7 @@ StmtResult Sema::BuildObjCAtThrowStmt(SourceLocation AtLoc, Expr *Throw) {
     if (Result.isInvalid())
       return StmtError();
 
-    Result = ActOnFinishFullExpr(Result.get(), /*DiscardedValue*/ false);
+    Result = ActOnFinishFullExpr(Result.get());
     if (Result.isInvalid())
       return StmtError();
     Throw = Result.get();
@@ -3863,7 +3876,7 @@ Sema::ActOnObjCAtSynchronizedOperand(SourceLocation atLoc, Expr *operand) {
   }
 
   // The operand to @synchronized is a full-expression.
-  return ActOnFinishFullExpr(operand, /*DiscardedValue*/ false);
+  return ActOnFinishFullExpr(operand);
 }
 
 StmtResult
diff --git a/lib/Sema/TreeTransform.h b/lib/Sema/TreeTransform.h
index df14768cbe..9de4e8d654 100644
--- a/lib/Sema/TreeTransform.h
+++ b/lib/Sema/TreeTransform.h
@@ -328,7 +328,7 @@ public:
   /// other mechanism.
   ///
   /// \returns the transformed statement.
-  StmtResult TransformStmt(Stmt *S, bool DiscardedValue = false);
+  StmtResult TransformStmt(Stmt *S);
 
   /// Transform the given statement.
   ///
@@ -3269,8 +3269,8 @@ private:
                                       bool DeducibleTSTContext);
 };
 
-template <typename Derived>
-StmtResult TreeTransform<Derived>::TransformStmt(Stmt *S, bool DiscardedValue) {
+template<typename Derived>
+StmtResult TreeTransform<Derived>::TransformStmt(Stmt *S) {
   if (!S)
     return S;
 
@@ -3294,7 +3294,7 @@ StmtResult TreeTransform<Derived>::TransformStmt(Stmt *S, bool DiscardedValue) {
       if (E.isInvalid())
         return StmtError();
 
-      return getSema().ActOnExprStmt(E, DiscardedValue);
+      return getSema().ActOnExprStmt(E);
     }
   }
 
@@ -4715,8 +4715,7 @@ TreeTransform<Derived>::TransformVariableArrayType(TypeLocBuilder &TLB,
   }
   if (SizeResult.isInvalid())
     return QualType();
-  SizeResult =
-      SemaRef.ActOnFinishFullExpr(SizeResult.get(), /*DiscardedValue*/ false);
+  SizeResult = SemaRef.ActOnFinishFullExpr(SizeResult.get());
   if (SizeResult.isInvalid())
     return QualType();
 
@@ -6521,9 +6520,7 @@ TreeTransform<Derived>::TransformCompoundStmt(CompoundStmt *S,
   bool SubStmtChanged = false;
   SmallVector<Stmt*, 8> Statements;
   for (auto *B : S->body()) {
-    StmtResult Result =
-        getDerived().TransformStmt(B, !IsStmtExpr || B != S->body_back());
-
+    StmtResult Result = getDerived().TransformStmt(B);
     if (Result.isInvalid()) {
       // Immediately fail if this was a DeclStmt, since it's very
       // likely that this will cause problems for future statements.
diff --git a/test/CXX/stmt.stmt/stmt.select/p3.cpp b/test/CXX/stmt.stmt/stmt.select/p3.cpp
index 4804cc559d..7a6a408ec9 100644
--- a/test/CXX/stmt.stmt/stmt.select/p3.cpp
+++ b/test/CXX/stmt.stmt/stmt.select/p3.cpp
@@ -1,5 +1,5 @@
-// RUN: %clang_cc1 -fsyntax-only -Wno-unused-value -verify %s
-// RUN: %clang_cc1 -fsyntax-only -Wno-unused-value -std=c++1z -Wc++14-compat -verify %s -DCPP17
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++1z -Wc++14-compat -verify %s -DCPP17
 
 int f();
 
@@ -71,6 +71,7 @@ void whileInitStatement() {
 // last loop above. It would be nice to remove this.
 void whileInitStatement2() {
   while (; false) {} // expected-error {{expected expression}}
-  // expected-error@-1 {{expected ';' after expression}}
-  // expected-error@-2 {{expected expression}}
+  // expected-warning@-1 {{expression result unused}}
+  // expected-error@-2 {{expected ';' after expression}}
+  // expected-error@-3 {{expected expression}}
 }
diff --git a/test/CodeCompletion/pragma-macro-token-caching.c b/test/CodeCompletion/pragma-macro-token-caching.c
index 59b6621b56..432706e85c 100644
--- a/test/CodeCompletion/pragma-macro-token-caching.c
+++ b/test/CodeCompletion/pragma-macro-token-caching.c
@@ -12,7 +12,7 @@ void completeParam(int param) {
 
 void completeParamPragmaError(int param) {
     Outer(__extension__({ _Pragma(2) })); // expected-error {{_Pragma takes a parenthesized string literal}}
-    param; // expected-warning {{expression result unused}}
+    param;
 }
 
 // RUN: %clang_cc1 -fsyntax-only -verify -code-completion-at=%s:16:1 %s | FileCheck %s
diff --git a/test/Parser/cxx1z-init-statement.cpp b/test/Parser/cxx1z-init-statement.cpp
index ade60dc762..3d119ef8e7 100644
--- a/test/Parser/cxx1z-init-statement.cpp
+++ b/test/Parser/cxx1z-init-statement.cpp
@@ -13,9 +13,9 @@ int f() {
   if (T(n) = 0; n) {}
 
   // init-statement expressions
-  if (T{f()}; f()) {} // expected-warning {{expression result unused}}
-  if (T{f()}, g, h; f()) {} // expected-warning 2{{unused}} expected-warning {{expression result unused}}
-  if (T(f()), g, h + 1; f()) {} // expected-warning 2{{unused}} expected-warning {{expression result unused}}
+  if (T{f()}; f()) {}
+  if (T{f()}, g, h; f()) {} // expected-warning 2{{unused}}
+  if (T(f()), g, h + 1; f()) {} // expected-warning 2{{unused}}
 
   // condition declarations
   if (T(n){g}) {}
@@ -35,7 +35,7 @@ int f() {
 
   // Likewise for 'switch'
   switch (int n; n) {}
-  switch (g; int g = 5) {} // expected-warning {{expression result unused}}
+  switch (g; int g = 5) {}
 
   if (int a, b; int c = a) { // expected-note 6{{previous}}
     int a; // expected-error {{redefinition}}
diff --git a/test/Parser/switch-recovery.cpp b/test/Parser/switch-recovery.cpp
index eacd017ab2..a3a0178cd1 100644
--- a/test/Parser/switch-recovery.cpp
+++ b/test/Parser/switch-recovery.cpp
@@ -105,7 +105,7 @@ void test9(int x) { // expected-note {{'x' declared here}}
               expected-error {{expected expression}}
     8:: x; // expected-error {{expected ';' after expression}} \
               expected-error {{no member named 'x' in the global namespace; did you mean simply 'x'?}} \
-              expected-warning {{expression result unused}}
+              expected-warning 2 {{expression result unused}}
     9:: :y; // expected-error {{expected ';' after expression}} \
                expected-error {{expected unqualified-id}} \
                expected-warning {{expression result unused}}
diff --git a/test/SemaCXX/cxx1z-init-statement.cpp b/test/SemaCXX/cxx1z-init-statement.cpp
index eea2589ab7..d37acd08ce 100644
--- a/test/SemaCXX/cxx1z-init-statement.cpp
+++ b/test/SemaCXX/cxx1z-init-statement.cpp
@@ -1,5 +1,5 @@
-// RUN: %clang_cc1 -std=c++1z -Wno-unused-value -verify %s
-// RUN: %clang_cc1 -std=c++17 -Wno-unused-value -verify %s
+// RUN: %clang_cc1 -std=c++1z -verify %s
+// RUN: %clang_cc1 -std=c++17 -verify %s
 
 void testIf() {
   int x = 0;
@@ -12,7 +12,7 @@ void testIf() {
     int x = 0; // expected-error {{redefinition of 'x'}}
 
   if (x; int a = 0) ++a;
-  if (x, +x; int a = 0) // expected-note 2 {{previous definition is here}}
+  if (x, +x; int a = 0) // expected-note 2 {{previous definition is here}} expected-warning {{unused}}
     int a = 0; // expected-error {{redefinition of 'a'}}
   else
     int a = 0; // expected-error {{redefinition of 'a'}}
@@ -48,7 +48,7 @@ void testSwitch() {
       ++a;
   }
 
-  switch (x, +x; int a = 0) { // expected-note {{previous definition is here}}
+  switch (x, +x; int a = 0) { // expected-note {{previous definition is here}} expected-warning {{unused}}
     case 0:
       int a = 0; // expected-error {{redefinition of 'a'}} // expected-note {{previous definition is here}}
     case 1:
diff --git a/test/SemaCXX/for-range-examples.cpp b/test/SemaCXX/for-range-examples.cpp
index 5424b7a8ee..477789b56c 100644
--- a/test/SemaCXX/for-range-examples.cpp
+++ b/test/SemaCXX/for-range-examples.cpp
@@ -244,7 +244,7 @@ void foo ()
 { 
   int b = 1, a[b];
   a[0] = 0;
-  [&] { for (int c : a) 0; } (); // expected-warning {{expression result unused}}
+  [&] { for (int c : a) 0; } ();
 }
 
 
diff --git a/test/SemaCXX/warn-unused-result.cpp b/test/SemaCXX/warn-unused-result.cpp
index f1de4618a7..88f5ab1e85 100644
--- a/test/SemaCXX/warn-unused-result.cpp
+++ b/test/SemaCXX/warn-unused-result.cpp
@@ -33,36 +33,6 @@ void test() {
   const S &s4 = g1();
 }
 
-void testSubstmts(int i) {
-  switch (i) {
-  case 0:
-    f(); // expected-warning {{ignoring return value}}
-  default:
-    f(); // expected-warning {{ignoring return value}}
-  }
-
-  if (i)
-    f(); // expected-warning {{ignoring return value}}
-  else
-    f(); // expected-warning {{ignoring return value}}
-
-  while (i)
-    f(); // expected-warning {{ignoring return value}}
-
-  do
-    f(); // expected-warning {{ignoring return value}}
-  while (i);
-
-  for (f(); // expected-warning {{ignoring return value}}
-       ;
-       f() // expected-warning {{ignoring return value}}
-      )
-    f(); // expected-warning {{ignoring return value}}
-
-  f(),  // expected-warning {{ignoring return value}}
-  (void)f();
-}
-
 struct X {
  int foo() __attribute__((warn_unused_result));
 };
@@ -236,13 +206,3 @@ void f() {
   (void)++p;
 }
 } // namespace
-
-namespace PR39837 {
-[[clang::warn_unused_result]] int f(int);
-
-void g() {
-  int a[2];
-  for (int b : a)
-    f(b); // expected-warning {{ignoring return value}}
-}
-} // namespace PR39837