[clang] [Clang][Sema]:Fix musttail attribute on a function with not_tail_called attribute has no warning/error (PR #134465)

[Aaron Ballman via cfe-commits]

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@@ -717,6 +717,13 @@ bool Sema::checkMustTailAttr(const Stmt *St, const Attr &MTA) {
     return false;
   }
 
+  if (const FunctionDecl *CalleeDecl = CE->getDirectCallee();
+      CalleeDecl && CalleeDecl->hasAttr<NotTailCalledAttr>()) {
+    Diag(St->getBeginLoc(), diag::err_musttail_mismatch) << /*show-function-callee=*/true << CalleeDecl;
+    Diag(CalleeDecl->getLocation(), diag::note_musttail_disabled_by_not_tail_called) << CalleeDecl;
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AaronBallman wrote:

I don't feel strongly about reusing the existing diagnostic, this new note is fine by me.

https://github.com/llvm/llvm-project/pull/134465