[PATCH] D136777: llvm::zip should not require assignment operator

[Tomás Longeri via Phabricator via llvm-commits]

tlongeri created this revision.
tlongeri added a reviewer: mehdi_amini.
Herald added a project: All.
tlongeri requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D136777

Files:
  llvm/include/llvm/ADT/STLExtras.h


Index: llvm/include/llvm/ADT/STLExtras.h
===================================================================
--- llvm/include/llvm/ADT/STLExtras.h
+++ llvm/include/llvm/ADT/STLExtras.h
@@ -646,13 +646,13 @@
   }
 
   template <size_t... Ns>
-  decltype(iterators) tup_inc(std::index_sequence<Ns...>) const {
-    return std::tuple<Iters...>(std::next(std::get<Ns>(iterators))...);
+  void tup_inc(std::index_sequence<Ns...>) {
+    (++std::get<Ns>(iterators), ...);
   }
 
   template <size_t... Ns>
-  decltype(iterators) tup_dec(std::index_sequence<Ns...>) const {
-    return std::tuple<Iters...>(std::prev(std::get<Ns>(iterators))...);
+  void tup_dec(std::index_sequence<Ns...>) {
+    (--std::get<Ns>(iterators), ...);
   }
 
   template <size_t... Ns>
@@ -671,14 +671,14 @@
   }
 
   ZipType &operator++() {
-    iterators = tup_inc(std::index_sequence_for<Iters...>{});
+    tup_inc(std::index_sequence_for<Iters...>{});
     return *reinterpret_cast<ZipType *>(this);
   }
 
   ZipType &operator--() {
     static_assert(Base::IsBidirectional,
                   "All inner iterators must be at least bidirectional.");
-    iterators = tup_dec(std::index_sequence_for<Iters...>{});
+    tup_dec(std::index_sequence_for<Iters...>{});
     return *reinterpret_cast<ZipType *>(this);
   }
 
@@ -769,10 +769,9 @@
 
 namespace detail {
 template <typename Iter>
-Iter next_or_end(const Iter &I, const Iter &End) {
-  if (I == End)
-    return End;
-  return std::next(I);
+void increment_or_end(Iter &I, const Iter &End) {
+  if (I != End)
+    ++I;
 }
 
 template <typename Iter>
@@ -826,9 +825,8 @@
   }
 
   template <size_t... Ns>
-  decltype(iterators) tup_inc(std::index_sequence<Ns...>) const {
-    return std::tuple<Iters...>(
-        next_or_end(std::get<Ns>(iterators), std::get<Ns>(end_iterators))...);
+  void tup_inc(std::index_sequence<Ns...>) const {
+    (increment_or_end(std::get<Ns>(iterators), std::get<Ns>(end_iterators)), ...);
   }
 
 public:
@@ -841,7 +839,7 @@
   }
 
   zip_longest_iterator<Iters...> &operator++() {
-    iterators = tup_inc(std::index_sequence_for<Iters...>{});
+    tup_inc(std::index_sequence_for<Iters...>{});
     return *this;
   }
 


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