[STLExtras] Remove incorrect hack to make indexed_accessor_range operator== compatible with C++20

[usx95]

This partially reverts c312f02

The motivation behind this is unclear and the change predates the clang implementation of p2468r2 so I am not sure if it was ever intended to work. Rewritten template operators were broken since the beginning.

Moreover, moving away from friend would be beneficial as these would only accepted once clang revises its implementation for fixing #70210. It also helps in making sure that older compilers still compile LLVM (in C++20).

[llvmbot]

@llvm/pr-subscribers-llvm-adt

Author: Utkarsh Saxena (usx95)

Changes

This partially reverts c312f02

The motivation behind this is unclear and the change predates the clang implementation of https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2468r2.html so I am not sure if it was ever intended to work. Rewritten template operators were broken since the beginning.

Moreover, moving away from friend would be beneficial as these would only accepted once clang revises its implementation to fix #70210. It also helps in making sure that older compilers still compile LLVM.

---

Full diff: https://github.com/llvm/llvm-project/pull/72220.diff

1 Files Affected:

• (modified) llvm/include/llvm/ADT/STLExtras.h (+5-9)

diff --git a/llvm/include/llvm/ADT/STLExtras.h b/llvm/include/llvm/ADT/STLExtras.h
index 18bc4d108b156bf..e42b0e8d1b27b71 100644
--- a/llvm/include/llvm/ADT/STLExtras.h
+++ b/llvm/include/llvm/ADT/STLExtras.h
@@ -1291,15 +1291,11 @@ class indexed_accessor_range_base {
   }
 
   /// Compare this range with another.
-  template <typename OtherT>
-  friend bool operator==(const indexed_accessor_range_base &lhs,
-                         const OtherT &rhs) {
-    return std::equal(lhs.begin(), lhs.end(), rhs.begin(), rhs.end());
-  }
-  template <typename OtherT>
-  friend bool operator!=(const indexed_accessor_range_base &lhs,
-                         const OtherT &rhs) {
-    return !(lhs == rhs);
+  template <typename OtherT> bool operator==(const OtherT &rhs) const {
+    return std::equal(begin(), end(), rhs.begin(), rhs.end());
+  }
+  template <typename OtherT> bool operator!=(const OtherT &rhs) const {
+    return !(*this == rhs);
   }
 
   /// Return the size of this range.

[d0k]

Fine with me, but I suppose this will break older clangs just like e558be5 did. Is everyone building clang in C++20 mode on a newer version now?

[ilya-biryukov]

I am testing if our internal builds and the buildbot will break with this change. I have previously assumed they would break, but there were other patches flying around at the same time so maybe I had missed something. It'd be nice if we could land this change and it'd work with some released version of Clang and Clang at head.

I'll post the results of my investigation when I'm done.

[ilya-biryukov]

Both internal and buildbot builds should be fine after this change.
And they should keep working after #72213 lands because it does some extra checks to report those cases as warnings rather than errors (hence, won't break the builds either).

LGTM!