[llvm] Fixed build with C++20 standard (PR #169772)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-adt

Author: Vedran Miletić (vedranmiletic)

<details>
<summary>Changes</summary>

Overload for operator- in ADT iterator is now constrained with concept BaseT::IsRandomAccess.

Patch by Jonathan Wakely.

Fixes #<!-- -->139072.

---
Full diff: https://github.com/llvm/llvm-project/pull/169772.diff


1 Files Affected:

- (modified) llvm/include/llvm/ADT/iterator.h (+5-1) 


``````````diff
diff --git a/llvm/include/llvm/ADT/iterator.h b/llvm/include/llvm/ADT/iterator.h
index 6f0c42fe08bec..f55f9d4a3e7f2 100644
--- a/llvm/include/llvm/ADT/iterator.h
+++ b/llvm/include/llvm/ADT/iterator.h
@@ -267,7 +267,11 @@ class iterator_adaptor_base
     return *static_cast<DerivedT *>(this);
   }
   using BaseT::operator-;
-  difference_type operator-(const DerivedT &RHS) const {
+  difference_type operator-(const DerivedT &RHS) const
+#ifdef __cpp_concepts
+    requires(bool(BaseT::IsRandomAccess))
+#endif
+  {
     static_assert(
         BaseT::IsRandomAccess,
         "The '-' operator is only defined for random access iterators.");

``````````

</details>


https://github.com/llvm/llvm-project/pull/169772