[clang] [clang:ast] Suppress warning for unused var without assertions. (NFC) (PR #169822)

[Simon Pilgrim via cfe-commits]

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@@ -12181,6 +12181,7 @@ static bool evalShiftWithCount(
   QualType SourceTy = Call->getArg(0)->getType();
   QualType CountTy = Call->getArg(1)->getType();
   assert(SourceTy->isVectorType() && CountTy->isVectorType());
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RKSimon wrote:

```suggestion
  assert(SourceTy->isVectorType() && Call->getArg(1)->getType()->isVectorType());
```

https://github.com/llvm/llvm-project/pull/169822