[clang] [clang][Sema] Combine fallout warnings to just one warning (PR #127546)

[via cfe-commits]

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@@ -696,12 +661,12 @@ static void CheckFallThroughForBody(Sema &S, const Decl *D, const Stmt *Body,
   if (CD.checkDiagnostics(Diags, ReturnsVoid, HasNoReturn))
       return;
   SourceLocation LBrace = Body->getBeginLoc(), RBrace = Body->getEndLoc();
-  auto EmitDiag = [&](SourceLocation Loc, unsigned DiagID) {
+  auto EmitDiag = [&](SourceLocation Loc, unsigned DiagID, unsigned FunMode) {
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foxtran wrote:

Unfortunately, in `diag_FallThrough_HasNoReturn` case, we have one argument, and in `diag_FallThrough_ReturnsNonVoid` we have two arguments, so I just removed `EmitDiag` since it can not check how many arguments diag message have and use a proper branch. 

https://github.com/llvm/llvm-project/pull/127546