[llvm] [ADT] Require base equality in indexed_accessor_iterator::operator==() (PR #107856)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-adt

Author: Andrei Golubev (andrey-golubev)

<details>
<summary>Changes</summary>

Similarly to operator<(), equality-comparing iterators from different ranges must really be forbidden. The preconditions for being able to do `it1 < it2` and `it1 != it2` (or `it1 == it2` for the matter) ought to be the same. Thus, there's little sense in keeping explicit base object comparison in operator==() whilst having this is a precondition in operator<() and operator-() (e.g. used for std::distance() and such).

---
Full diff: https://github.com/llvm/llvm-project/pull/107856.diff


1 Files Affected:

- (modified) llvm/include/llvm/ADT/STLExtras.h (+2-1) 


``````````diff
diff --git a/llvm/include/llvm/ADT/STLExtras.h b/llvm/include/llvm/ADT/STLExtras.h
index e11d6cac7685e4..eb441bb31c9bc8 100644
--- a/llvm/include/llvm/ADT/STLExtras.h
+++ b/llvm/include/llvm/ADT/STLExtras.h
@@ -1194,7 +1194,8 @@ class indexed_accessor_iterator
     return index - rhs.index;
   }
   bool operator==(const indexed_accessor_iterator &rhs) const {
-    return base == rhs.base && index == rhs.index;
+    assert(base == rhs.base && "incompatible iterators");
+    return index == rhs.index;
   }
   bool operator<(const indexed_accessor_iterator &rhs) const {
     assert(base == rhs.base && "incompatible iterators");

``````````

</details>


https://github.com/llvm/llvm-project/pull/107856