[clang] [clang][Sema] Recheck array size once the element type is complete (PR #219817)

[Erich Keane via cfe-commits]

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@@ -9688,6 +9688,28 @@ static void assignInheritanceModel(Sema &S, CXXRecordDecl *RD) {
   }
 }
 
+/// Return the (possibly nested) constant array type in \p T whose size cannot
+/// be represented, if any. BuildArrayType can only check the element count if
+/// the element type is still incomplete when the array type is formed.
+static const ConstantArrayType *findArrayTypeTooLarge(const ASTContext &Context,
+                                                      QualType T) {
+  const auto *CAT = dyn_cast<ConstantArrayType>(T.getCanonicalType());
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erichkeane wrote:

You can't do dyn_cast here.  you have to use `getAsConstantArrayType`.

https://github.com/llvm/llvm-project/pull/219817