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.

llvm-svn: 350404

1 files changed, 33 insertions, 22 deletions

diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index 78bef59ff6f..59c4b49bfb1 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -5320,7 +5320,7 @@ 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());
+    EUB = SemaRef.ActOnFinishFullExpr(EUB.get(), /*DiscardedValue*/ false);
 
     // 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
@@ -5349,7 +5349,8 @@ 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());
+      CombEUB =
+          SemaRef.ActOnFinishFullExpr(CombEUB.get(), /*DiscardedValue*/ false);
 
       const CapturedDecl *CD = cast<CapturedStmt>(AStmt)->getCapturedDecl();
       // We expect to have at least 2 more parameters than the 'parallel'
@@ -5383,7 +5384,7 @@ 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());
+    Init = SemaRef.ActOnFinishFullExpr(Init.get(), /*DiscardedValue*/ false);
 
     if (isOpenMPLoopBoundSharingDirective(DKind)) {
       Expr *CombRHS =
@@ -5394,7 +5395,8 @@ 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());
+      CombInit =
+          SemaRef.ActOnFinishFullExpr(CombInit.get(), /*DiscardedValue*/ false);
     }
   }
 
@@ -5426,7 +5428,7 @@ 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());
+  Inc = SemaRef.ActOnFinishFullExpr(Inc.get(), /*DiscardedValue*/ false);
   if (!Inc.isUsable())
     return 0;
 
@@ -5444,7 +5446,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
     // LB = LB + ST
     NextLB =
         SemaRef.BuildBinOp(CurScope, IncLoc, BO_Assign, LB.get(), NextLB.get());
-    NextLB = SemaRef.ActOnFinishFullExpr(NextLB.get());
+    NextLB =
+        SemaRef.ActOnFinishFullExpr(NextLB.get(), /*DiscardedValue*/ false);
     if (!NextLB.isUsable())
       return 0;
     // UB + ST
@@ -5454,7 +5457,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
     // UB = UB + ST
     NextUB =
         SemaRef.BuildBinOp(CurScope, IncLoc, BO_Assign, UB.get(), NextUB.get());
-    NextUB = SemaRef.ActOnFinishFullExpr(NextUB.get());
+    NextUB =
+        SemaRef.ActOnFinishFullExpr(NextUB.get(), /*DiscardedValue*/ false);
     if (!NextUB.isUsable())
       return 0;
     if (isOpenMPLoopBoundSharingDirective(DKind)) {
@@ -5465,7 +5469,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
       // LB = LB + ST
       CombNextLB = SemaRef.BuildBinOp(CurScope, IncLoc, BO_Assign, CombLB.get(),
                                       CombNextLB.get());
-      CombNextLB = SemaRef.ActOnFinishFullExpr(CombNextLB.get());
+      CombNextLB = SemaRef.ActOnFinishFullExpr(CombNextLB.get(),
+                                               /*DiscardedValue*/ false);
       if (!CombNextLB.isUsable())
         return 0;
       // UB + ST
@@ -5476,7 +5481,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
       // UB = UB + ST
       CombNextUB = SemaRef.BuildBinOp(CurScope, IncLoc, BO_Assign, CombUB.get(),
                                       CombNextUB.get());
-      CombNextUB = SemaRef.ActOnFinishFullExpr(CombNextUB.get());
+      CombNextUB = SemaRef.ActOnFinishFullExpr(CombNextUB.get(),
+                                               /*DiscardedValue*/ false);
       if (!CombNextUB.isUsable())
         return 0;
     }
@@ -5497,7 +5503,8 @@ 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());
+    DistInc =
+        SemaRef.ActOnFinishFullExpr(DistInc.get(), /*DiscardedValue*/ false);
     assert(DistInc.isUsable() && "distribute inc expr was not built");
 
     // Build expression: UB = min(UB, prevUB) for #for in composite or combined
@@ -5509,7 +5516,8 @@ 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());
+    PrevEUB =
+        SemaRef.ActOnFinishFullExpr(PrevEUB.get(), /*DiscardedValue*/ false);
 
     // Build IV <= PrevUB to be used in parallel for is in combination with
     // a distribute directive with schedule(static, 1)
@@ -5613,8 +5621,10 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
   Built.IterationVarRef = IV.get();
   Built.LastIteration = LastIteration.get();
   Built.NumIterations = NumIterations.get();
-  Built.CalcLastIteration =
-      SemaRef.ActOnFinishFullExpr(CalcLastIteration.get()).get();
+  Built.CalcLastIteration = SemaRef
+                                .ActOnFinishFullExpr(CalcLastIteration.get(),
+                                                     /*DiscardedValue*/ false)
+                                .get();
   Built.PreCond = PreCond.get();
   Built.PreInits = buildPreInits(C, Captures);
   Built.Cond = Cond.get();
@@ -10267,8 +10277,8 @@ OMPClause *Sema::ActOnOpenMPLastprivateClause(ArrayRef<Expr *> VarList,
                                          PseudoDstExpr, PseudoSrcExpr);
     if (AssignmentOp.isInvalid())
       continue;
-    AssignmentOp = ActOnFinishFullExpr(AssignmentOp.get(), ELoc,
-                                       /*DiscardedValue=*/true);
+    AssignmentOp =
+        ActOnFinishFullExpr(AssignmentOp.get(), ELoc, /*DiscardedValue*/ false);
     if (AssignmentOp.isInvalid())
       continue;
 
@@ -11274,7 +11284,8 @@ static bool actOnOMPReductionKindClause(
                            BO_Assign, LHSDRE, ConditionalOp);
         }
         if (ReductionOp.isUsable())
-          ReductionOp = S.ActOnFinishFullExpr(ReductionOp.get());
+          ReductionOp = S.ActOnFinishFullExpr(ReductionOp.get(),
+                                              /*DiscardedValue*/ false);
       }
       if (!ReductionOp.isUsable())
         continue;
@@ -11612,7 +11623,7 @@ OMPClause *Sema::ActOnOpenMPLinearClause(
         buildDeclRefExpr(*this, SaveVar, StepExpr->getType(), StepLoc);
     ExprResult CalcStep =
         BuildBinOp(CurScope, StepLoc, BO_Assign, SaveRef.get(), StepExpr);
-    CalcStep = ActOnFinishFullExpr(CalcStep.get());
+    CalcStep = ActOnFinishFullExpr(CalcStep.get(), /*DiscardedValue*/ false);
 
     // Warn about zero linear step (it would be probably better specified as
     // making corresponding variables 'const').
@@ -11700,7 +11711,7 @@ static bool FinishOpenMPLinearClause(OMPLinearClause &Clause, DeclRefExpr *IV,
     else
       Update = *CurPrivate;
     Update = SemaRef.ActOnFinishFullExpr(Update.get(), DE->getBeginLoc(),
-                                         /*DiscardedValue=*/true);
+                                         /*DiscardedValue*/ false);
 
     // Build final: Var = InitExpr + NumIterations * Step
     ExprResult Final;
@@ -11711,7 +11722,7 @@ static bool FinishOpenMPLinearClause(OMPLinearClause &Clause, DeclRefExpr *IV,
     else
       Final = *CurPrivate;
     Final = SemaRef.ActOnFinishFullExpr(Final.get(), DE->getBeginLoc(),
-                                        /*DiscardedValue=*/true);
+                                        /*DiscardedValue*/ false);
 
     if (!Update.isUsable() || !Final.isUsable()) {
       Updates.push_back(nullptr);
@@ -11879,7 +11890,7 @@ OMPClause *Sema::ActOnOpenMPCopyinClause(ArrayRef<Expr *> VarList,
     if (AssignmentOp.isInvalid())
       continue;
     AssignmentOp = ActOnFinishFullExpr(AssignmentOp.get(), DE->getExprLoc(),
-                                       /*DiscardedValue=*/true);
+                                       /*DiscardedValue*/ false);
     if (AssignmentOp.isInvalid())
       continue;
 
@@ -11987,8 +11998,8 @@ OMPClause *Sema::ActOnOpenMPCopyprivateClause(ArrayRef<Expr *> VarList,
         DSAStack->getCurScope(), ELoc, BO_Assign, PseudoDstExpr, PseudoSrcExpr);
     if (AssignmentOp.isInvalid())
       continue;
-    AssignmentOp = ActOnFinishFullExpr(AssignmentOp.get(), ELoc,
-                                       /*DiscardedValue=*/true);
+    AssignmentOp =
+        ActOnFinishFullExpr(AssignmentOp.get(), ELoc, /*DiscardedValue*/ false);
     if (AssignmentOp.isInvalid())
       continue;