[clang] [clang] Save ShuffleVectorExpr args as ConstantExpr (PR #139709)

[Shafik Yaghmour via cfe-commits]

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@@ -4566,9 +4566,11 @@ class ShuffleVectorExpr : public Expr {
 
   void setExprs(const ASTContext &C, ArrayRef<Expr *> Exprs);
 
-  llvm::APSInt getShuffleMaskIdx(const ASTContext &Ctx, unsigned N) const {
+  llvm::APSInt getShuffleMaskIdx(unsigned N) const {
     assert((N < NumExprs - 2) && "Shuffle idx out of range!");
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shafik wrote:

I am looking at `NumExprs - 2` and I can't find where we ever assert or enforce `NumExprs` is always 2 or more.

https://github.com/llvm/llvm-project/pull/139709