[PATCH] D53793: [ADT] Remove illegal comparison of singular iterators from SmallSetTest

[Eugene Sharygin via Phabricator via llvm-commits]

eush created this revision.
eush added reviewers: fhahn, dblaikie, chandlerc.
Herald added a subscriber: dexonsmith.

This removes the assertion that a copy of a moved-from SmallSetIterator
equals the original, which is illegal due to SmallSetIterator including
an instance of a standard `std::set` iterator.

C++ [iterator.requirements.general] states that comparing singular
iterators has undefined result:

  Iterators can also have singular values that are not associated with
  any sequence. [...] Results of most expressions are undefined for
  singular values; the only exceptions are destroying an iterator that
  holds a singular value, the assignment of a non-singular value to an
  iterator that holds a singular value, and, for iterators that satisfy
  the Cpp17DefaultConstructible requirements, using a value-initialized
  iterator as the source of a copy or move operation.

This assertion triggers the following error in the GNU C++ Library in
debug mode under EXPENSIVE_CHECKS:

  /usr/include/c++/8.2.1/debug/safe_iterator.h:518:
  Error: attempt to compare a singular iterator to a singular iterator.
  
  Objects involved in the operation:
      iterator "lhs" @ 0x0x7fff86420670 {
        state = singular;
      }
      iterator "rhs" @ 0x0x7fff86420640 {
        state = singular;
      }


Repository:
  rL LLVM

https://reviews.llvm.org/D53793

Files:
  unittests/ADT/SmallSetTest.cpp


Index: unittests/ADT/SmallSetTest.cpp
===================================================================
--- unittests/ADT/SmallSetTest.cpp
+++ unittests/ADT/SmallSetTest.cpp
@@ -142,8 +142,4 @@
   auto Iter2 = s1.begin();
   Iter = std::move(Iter2);
   EXPECT_EQ("str 0", *Iter);
-
-  auto Iter3 = s1.end();
-  Iter3 = Iter2;
-  EXPECT_EQ(Iter3, Iter2);
 }


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