Implement P1771
As passed in the Cologne meeting and treated by Core as a DR,
[[nodiscard]] was applied to constructors so that they can be diagnosed
in cases where the user forgets a variable name for a type.
The intent is to enable the library to start using this on the
constructors of scope_guard/lock_guard.
Differential Revision: https://reviews.llvm.org/D64914
llvm-svn: 367027
diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index 3400f7d..94a1ccc 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -196,6 +196,25 @@
return true;
}
+static bool DiagnoseNoDiscard(Sema &S, const WarnUnusedResultAttr *A,
+ SourceLocation Loc, SourceRange R1,
+ SourceRange R2, bool IsCtor) {
+ if (!A)
+ return false;
+ StringRef Msg = A->getMessage();
+
+ if (Msg.empty()) {
+ if (IsCtor)
+ return S.Diag(Loc, diag::warn_unused_constructor) << A << R1 << R2;
+ return S.Diag(Loc, diag::warn_unused_result) << A << R1 << R2;
+ }
+
+ if (IsCtor)
+ return S.Diag(Loc, diag::warn_unused_constructor_msg) << A << Msg << R1
+ << R2;
+ return S.Diag(Loc, diag::warn_unused_result_msg) << A << Msg << R1 << R2;
+}
+
void Sema::DiagnoseUnusedExprResult(const Stmt *S) {
if (const LabelStmt *Label = dyn_cast_or_null<LabelStmt>(S))
return DiagnoseUnusedExprResult(Label->getSubStmt());
@@ -254,19 +273,19 @@
return;
E = WarnExpr;
+ if (const auto *Cast = dyn_cast<CastExpr>(E))
+ if (Cast->getCastKind() == CK_NoOp ||
+ Cast->getCastKind() == CK_ConstructorConversion)
+ E = Cast->getSubExpr()->IgnoreImpCasts();
+
if (const CallExpr *CE = dyn_cast<CallExpr>(E)) {
if (E->getType()->isVoidType())
return;
- if (const auto *A = cast_or_null<WarnUnusedResultAttr>(
- CE->getUnusedResultAttr(Context))) {
- StringRef Msg = A->getMessage();
- if (!Msg.empty())
- Diag(Loc, diag::warn_unused_result_msg) << A << Msg << R1 << R2;
- else
- Diag(Loc, diag::warn_unused_result) << A << R1 << R2;
+ if (DiagnoseNoDiscard(*this, cast_or_null<WarnUnusedResultAttr>(
+ CE->getUnusedResultAttr(Context)),
+ Loc, R1, R2, /*isCtor=*/false))
return;
- }
// If the callee has attribute pure, const, or warn_unused_result, warn with
// a more specific message to make it clear what is happening. If the call
@@ -284,9 +303,24 @@
return;
}
}
+ } else if (const auto *CE = dyn_cast<CXXConstructExpr>(E)) {
+ if (const CXXConstructorDecl *Ctor = CE->getConstructor()) {
+ const auto *A = Ctor->getAttr<WarnUnusedResultAttr>();
+ A = A ? A : Ctor->getParent()->getAttr<WarnUnusedResultAttr>();
+ if (DiagnoseNoDiscard(*this, A, Loc, R1, R2, /*isCtor=*/true))
+ return;
+ }
+ } else if (const auto *ILE = dyn_cast<InitListExpr>(E)) {
+ if (const TagDecl *TD = ILE->getType()->getAsTagDecl()) {
+
+ if (DiagnoseNoDiscard(*this, TD->getAttr<WarnUnusedResultAttr>(), Loc, R1,
+ R2, /*isCtor=*/false))
+ return;
+ }
} else if (ShouldSuppress)
return;
+ E = WarnExpr;
if (const ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(E)) {
if (getLangOpts().ObjCAutoRefCount && ME->isDelegateInitCall()) {
Diag(Loc, diag::err_arc_unused_init_message) << R1;
@@ -294,14 +328,9 @@
}
const ObjCMethodDecl *MD = ME->getMethodDecl();
if (MD) {
- if (const auto *A = MD->getAttr<WarnUnusedResultAttr>()) {
- StringRef Msg = A->getMessage();
- if (!Msg.empty())
- Diag(Loc, diag::warn_unused_result_msg) << A << Msg << R1 << R2;
- else
- Diag(Loc, diag::warn_unused_result) << A << R1 << R2;
+ if (DiagnoseNoDiscard(*this, MD->getAttr<WarnUnusedResultAttr>(), Loc, R1,
+ R2, /*isCtor=*/false))
return;
- }
}
} else if (const PseudoObjectExpr *POE = dyn_cast<PseudoObjectExpr>(E)) {
const Expr *Source = POE->getSyntacticForm();