[Sema] Fix lifetime extension for temporaries in range-based for loops in C++23 (#145164)

C++23 mandates that temporaries used in range-based for loops are
lifetime-extended
to cover the full loop. This patch adds a check for loop variables and
compiler-
generated `__range` bindings to apply the correct extension.

Includes test cases based on examples from CWG900/P2644R1.

Fixes https://github.com/llvm/llvm-project/issues/109793

1 files changed, 2 insertions, 0 deletions

diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index b8a68af..e414910 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -1317,6 +1317,7 @@ void ASTDeclWriter::VisitVarDecl(VarDecl *D) {
       VarDeclBits.addBits(0, /*Width=*/3);
 
     VarDeclBits.addBit(D->isObjCForDecl());
+    VarDeclBits.addBit(D->isCXXForRangeImplicitVar());
   }
 
   Record.push_back(VarDeclBits);
@@ -2738,6 +2739,7 @@ void ASTWriter::WriteDeclAbbrevs() {
             // isInline, isInlineSpecified, isConstexpr,
             // isInitCapture, isPrevDeclInSameScope, hasInitWithSideEffects,
             // EscapingByref, HasDeducedType, ImplicitParamKind, isObjCForDecl
+            // IsCXXForRangeImplicitVar
   Abv->Add(BitCodeAbbrevOp(0));                         // VarKind (local enum)
   // Type Source Info
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));