[clang] [Clang] Extend lifetime of temporaries in mem-default-init for P2718R0 (PR #86960)

[Eli Friedman via cfe-commits]

================
@@ -1230,11 +1230,26 @@ CodeGenFunction::EmitCXXForRangeStmt(const CXXForRangeStmt &S,
   JumpDest LoopExit = getJumpDestInCurrentScope("for.end");
 
   LexicalScope ForScope(*this, S.getSourceRange());
+  const DeclStmt *RangeDS = cast<DeclStmt>(S.getRangeStmt());
+  const VarDecl *RangeVar = cast<VarDecl>(RangeDS->getSingleDecl());
+  if (getLangOpts().CPlusPlus23)
----------------
efriedma-quic wrote:

Oh, so it's actually supposed to say "If a temporary expression is bound to a reference member from a default member initializer, and that member initializer is used by a constructor, the constructor is ill-formed" or something like that?  I guess that makes sense in context, but the language could be improved.

Back to the issue we were discussing here, when are the destructors for non-lifetime-extended temporaries supposed to run?  If they're supposed to stay live for the whole expression, probably the rewriting code in Sema should just rewrite out the ExprWithCleanups.

If they're supposed to be destroyed, you might need to add a special-case to ExprWithCleanups handling to special-case the cleanups for the temporaries that are supposed to be lifetime-extended.  (If you're going to touch this code, make sure you're working on latest main, since #85398 landed recently.)

https://github.com/llvm/llvm-project/pull/86960