[clang] [BoundsSafety][Sema] Allow counted_by and counted_by_or_null on pointers where the pointee type is incomplete but potentially completable (PR #106321)

[Erich Keane via cfe-commits]

================
@@ -186,4 +218,370 @@ bool Sema::CheckCountedByAttrOnField(FieldDecl *FD, Expr *E, bool CountInBytes,
   return false;
 }
 
+SourceRange Sema::BoundsSafetySourceRangeFor(const CountAttributedType *CATy) {
+  // Note: This implementation relies on `CountAttributedType` being unique.
+  // E.g.:
+  //
+  // struct Foo {
+  //   int count;
+  //   char* __counted_by(count) buffer;
+  //   char* __counted_by(count) buffer2;
+  // };
+  //
+  // The types of `buffer` and `buffer2` are unique. The types being
+  // unique means the SourceLocation of the `counted_by` expression can be used
+  // to find where the attribute was written.
+
+  auto Fallback = CATy->getCountExpr()->getSourceRange();
----------------
erichkeane wrote:

I don't think 'auto' is supposed to be used in most of the uses in the function here.

https://github.com/llvm/llvm-project/pull/106321