Introduce a new kind of failed result for isLvalue/isModifiableLvalue

which describes temporary objects of class type in C++. Use this to
provide a more-specific, remappable diagnostic when takin the address
of such a temporary.

llvm-svn: 96396

1 files changed, 29 insertions, 2 deletions

diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index 4cb0aa4560d..fac65064c07 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -1120,8 +1120,15 @@ Expr::isLvalueResult Expr::isLvalueInternal(ASTContext &Ctx) const {
       return LV_Valid;
     break;
   case ImplicitCastExprClass:
-    return cast<ImplicitCastExpr>(this)->isLvalueCast()? LV_Valid
-                                                       : LV_InvalidExpression;
+    if (cast<ImplicitCastExpr>(this)->isLvalueCast())
+      return LV_Valid;
+
+    // If this is a conversion to a class temporary, make a note of
+    // that.
+    if (Ctx.getLangOptions().CPlusPlus && getType()->isRecordType())
+      return LV_ClassTemporary;
+
+    break;
   case ParenExprClass: // C99 6.5.1p5
     return cast<ParenExpr>(this)->getSubExpr()->isLvalue(Ctx);
   case BinaryOperatorClass:
@@ -1171,9 +1178,15 @@ Expr::isLvalueResult Expr::isLvalueInternal(ASTContext &Ctx) const {
     if (ReturnType->isLValueReferenceType())
       return LV_Valid;
 
+    // If the function is returning a class temporary, make a note of
+    // that.
+    if (Ctx.getLangOptions().CPlusPlus && ReturnType->isRecordType())
+      return LV_ClassTemporary;
+
     break;
   }
   case CompoundLiteralExprClass: // C99 6.5.2.5p5
+    // FIXME: Is this what we want in C++?
     return LV_Valid;
   case ChooseExprClass:
     // __builtin_choose_expr is an lvalue if the selected operand is.
@@ -1207,6 +1220,13 @@ Expr::isLvalueResult Expr::isLvalueInternal(ASTContext &Ctx) const {
     if (cast<ExplicitCastExpr>(this)->getTypeAsWritten()->
           isLValueReferenceType())
       return LV_Valid;
+
+    // If this is a conversion to a class temporary, make a note of
+    // that.
+    if (Ctx.getLangOptions().CPlusPlus && 
+        cast<ExplicitCastExpr>(this)->getTypeAsWritten()->isRecordType())
+      return LV_ClassTemporary;
+
     break;
   case CXXTypeidExprClass:
     // C++ 5.2.8p1: The result of a typeid expression is an lvalue of ...
@@ -1253,6 +1273,11 @@ Expr::isLvalueResult Expr::isLvalueInternal(ASTContext &Ctx) const {
         return LV_Valid;
     break;
 
+  case Expr::CXXConstructExprClass:
+  case Expr::CXXTemporaryObjectExprClass:
+  case Expr::CXXZeroInitValueExprClass:
+    return LV_ClassTemporary;
+
   default:
     break;
   }
@@ -1296,6 +1321,8 @@ Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const {
   case LV_SubObjCPropertySetting: return MLV_SubObjCPropertySetting;
   case LV_SubObjCPropertyGetterSetting: 
     return MLV_SubObjCPropertyGetterSetting;
+  case LV_ClassTemporary:
+    return MLV_ClassTemporary;
   }
 
   // The following is illegal: