Minor cleanup

include/fmt/format.h

@@ -752,12 +752,11 @@ template <typename T> struct allocator : private std::decay<void> {
 
   void deallocate(T* p, size_t) { std::free(p); }
 
-  FMT_CONSTEXPR20 friend bool operator==(allocator, allocator) noexcept {
+  constexpr friend auto operator==(allocator, allocator) noexcept -> bool {
     return true;  // All instances of this allocator are equivalent.
   }
-
-  FMT_CONSTEXPR20 friend bool operator!=(allocator a, allocator b) noexcept {
-    return !(a == b);
+  constexpr friend auto operator!=(allocator, allocator) noexcept -> bool {
+    return false;
   }
 };
 
@@ -834,42 +833,32 @@ class basic_memory_buffer : public detail::buffer<T> {
   FMT_CONSTEXPR20 ~basic_memory_buffer() { deallocate(); }
 
  private:
-  template <typename Alloc = Allocator>
-  FMT_CONSTEXPR20
-      typename std::enable_if<std::allocator_traits<Alloc>::
-                                  propagate_on_container_move_assignment::value,
-                              bool>::type
-      allocator_move_impl(basic_memory_buffer& other) {
+  template <typename Alloc = Allocator,
+            FMT_ENABLE_IF(std::allocator_traits<Alloc>::
+                              propagate_on_container_move_assignment::value)>
+  FMT_CONSTEXPR20 auto move_alloc(basic_memory_buffer& other) -> bool {
     alloc_ = std::move(other.alloc_);
     return true;
   }
-  // If the allocator does not propagate,
-  // then copy the content from source buffer.
-  template <typename Alloc = Allocator>
-  FMT_CONSTEXPR20
-      typename std::enable_if<!std::allocator_traits<Alloc>::
-                                  propagate_on_container_move_assignment::value,
-                              bool>::type
-      allocator_move_impl(basic_memory_buffer& other) {
+  // If the allocator does not propagate then copy the data from other.
+  template <typename Alloc = Allocator,
+            FMT_ENABLE_IF(!std::allocator_traits<Alloc>::
+                              propagate_on_container_move_assignment::value)>
+  FMT_CONSTEXPR20 auto move_alloc(basic_memory_buffer& other) -> bool {
     T* data = other.data();
-    if (alloc_ != other.alloc_ && data != other.store_) {
-      size_t size = other.size();
-      // Perform copy operation, allocators are different
-      this->resize(size);
-      detail::copy<T>(data, data + size, this->data());
-      return false;
-    }
-    return true;
+    if (alloc_ == other.alloc_ || data == other.store_) return true;
+    size_t size = other.size();
+    // Perform copy operation, allocators are different.
+    this->resize(size);
+    detail::copy<T>(data, data + size, this->data());
+    return false;
   }
 
   // Move data from other to this buffer.
   FMT_CONSTEXPR20 void move(basic_memory_buffer& other) {
     T* data = other.data();
     size_t size = other.size(), capacity = other.capacity();
-    // Replicate the behaviour of std library containers
-    if (!allocator_move_impl(other)) {
-      return;
-    }
+    if (!move_alloc(other)) return;
     if (data == other.store_) {
       this->set(store_, capacity);
       detail::copy<T>(other.store_, other.store_ + size, store_);