DR616, and part of P0135R1: member access (or pointer-to-member access) on a

temporary produces an xvalue, not a prvalue. Support this by materializing the
temporary prior to performing the member access.

llvm-svn: 288563

4 files changed, 40 insertions, 16 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 667ea6cb4e3..4415100ab45 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -9810,8 +9810,8 @@ static bool IsReadonlyMessage(Expr *E, Sema &S) {
   const MemberExpr *ME = dyn_cast<MemberExpr>(E);
   if (!ME) return false;
   if (!isa<FieldDecl>(ME->getMemberDecl())) return false;
-  ObjCMessageExpr *Base =
-    dyn_cast<ObjCMessageExpr>(ME->getBase()->IgnoreParenImpCasts());
+  ObjCMessageExpr *Base = dyn_cast<ObjCMessageExpr>(
+      ME->getBase()->IgnoreImplicit()->IgnoreParenImpCasts());
   if (!Base) return false;
   return Base->getMethodDecl() != nullptr;
 }
@@ -9894,7 +9894,7 @@ static void DiagnoseConstAssignment(Sema &S, const Expr *E,
   while (true) {
     IsDereference = NextIsDereference;
 
-    E = E->IgnoreParenImpCasts();
+    E = E->IgnoreImplicit()->IgnoreParenImpCasts();
     if (const MemberExpr *ME = dyn_cast<MemberExpr>(E)) {
       NextIsDereference = ME->isArrow();
       const ValueDecl *VD = ME->getMemberDecl();
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 79b5356d79d..28ccd607507 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -4984,11 +4984,14 @@ QualType Sema::CheckPointerToMemberOperands(ExprResult &LHS, ExprResult &RHS,
          !RHS.get()->getType()->isPlaceholderType() &&
          "placeholders should have been weeded out by now");
 
-  // The LHS undergoes lvalue conversions if this is ->*.
-  if (isIndirect) {
+  // The LHS undergoes lvalue conversions if this is ->*, and undergoes the
+  // temporary materialization conversion otherwise.
+  if (isIndirect)
     LHS = DefaultLvalueConversion(LHS.get());
-    if (LHS.isInvalid()) return QualType();
-  }
+  else if (LHS.get()->isRValue())
+    LHS = TemporaryMaterializationConversion(LHS.get());
+  if (LHS.isInvalid())
+    return QualType();
 
   // The RHS always undergoes lvalue conversions.
   RHS = DefaultLvalueConversion(RHS.get());
diff --git a/clang/lib/Sema/SemaExprMember.cpp b/clang/lib/Sema/SemaExprMember.cpp
index eddf0d69a22..806a3d813ee 100644
--- a/clang/lib/Sema/SemaExprMember.cpp
+++ b/clang/lib/Sema/SemaExprMember.cpp
@@ -969,6 +969,15 @@ Sema::BuildMemberReferenceExpr(Expr *BaseExpr, QualType BaseExprType,
     BaseType = BaseType->castAs<PointerType>()->getPointeeType();
   }
   R.setBaseObjectType(BaseType);
+
+  // C++1z [expr.ref]p2:
+  //   For the first option (dot) the first expression shall be a glvalue [...]
+  if (!IsArrow && BaseExpr->isRValue()) {
+    ExprResult Converted = TemporaryMaterializationConversion(BaseExpr);
+    if (Converted.isInvalid())
+      return ExprError();
+    BaseExpr = Converted.get();
+  }
   
   LambdaScopeInfo *const CurLSI = getCurLambda();
   // If this is an implicit member reference and the overloaded
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index f5e38b4fbdf..3937aad012d 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -5963,10 +5963,7 @@ performReferenceExtension(Expr *Init,
 
     // Step over any subobject adjustments; we may have a materialized
     // temporary inside them.
-    SmallVector<const Expr *, 2> CommaLHSs;
-    SmallVector<SubobjectAdjustment, 2> Adjustments;
-    Init = const_cast<Expr *>(
-        Init->skipRValueSubobjectAdjustments(CommaLHSs, Adjustments));
+    Init = const_cast<Expr *>(Init->skipRValueSubobjectAdjustments());
 
     // Per current approach for DR1376, look through casts to reference type
     // when performing lifetime extension.
@@ -5996,10 +5993,7 @@ performReferenceExtension(Expr *Init,
 static void performLifetimeExtension(Expr *Init,
                                      const InitializedEntity *ExtendingEntity) {
   // Dig out the expression which constructs the extended temporary.
-  SmallVector<const Expr *, 2> CommaLHSs;
-  SmallVector<SubobjectAdjustment, 2> Adjustments;
-  Init = const_cast<Expr *>(
-      Init->skipRValueSubobjectAdjustments(CommaLHSs, Adjustments));
+  Init = const_cast<Expr *>(Init->skipRValueSubobjectAdjustments());
 
   if (CXXBindTemporaryExpr *BTE = dyn_cast<CXXBindTemporaryExpr>(Init))
     Init = BTE->getSubExpr();
@@ -6218,6 +6212,22 @@ Sema::CreateMaterializeTemporaryExpr(QualType T, Expr *Temporary,
   return MTE;
 }
 
+ExprResult Sema::TemporaryMaterializationConversion(Expr *E) {
+  // In C++98, we don't want to implicitly create an xvalue.
+  // FIXME: This means that AST consumers need to deal with "prvalues" that
+  // denote materialized temporaries. Maybe we should add another ValueKind
+  // for "xvalue pretending to be a prvalue" for C++98 support.
+  if (!E->isRValue() || !getLangOpts().CPlusPlus11)
+    return E;
+
+  // C++1z [conv.rval]/1: T shall be a complete type.
+  QualType T = E->getType();
+  if (RequireCompleteType(E->getExprLoc(), T, diag::err_incomplete_type))
+    return ExprError();
+
+  return CreateMaterializeTemporaryExpr(E->getType(), E, false);
+}
+
 ExprResult
 InitializationSequence::Perform(Sema &S,
                                 const InitializedEntity &Entity,
@@ -6316,7 +6326,9 @@ InitializationSequence::Perform(Sema &S,
   if (Args.size() == 1 && Args[0]->getType()->isArrayType() &&
       Entity.getType()->isPointerType() &&
       InitializedEntityOutlivesFullExpression(Entity)) {
-    Expr *Init = Args[0];
+    const Expr *Init = Args[0]->skipRValueSubobjectAdjustments();
+    if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(Init))
+      Init = MTE->GetTemporaryExpr();
     Expr::LValueClassification Kind = Init->ClassifyLValue(S.Context);
     if (Kind == Expr::LV_ClassTemporary || Kind == Expr::LV_ArrayTemporary)
       S.Diag(Init->getLocStart(), diag::warn_temporary_array_to_pointer_decay)