Address philnik777's suggestions

Author: winner245

libcxx/include/string

@@ -2360,8 +2360,14 @@ private:
     size_type __old_size = size();
     if (__n > __old_size)
       __annotate_increase(__n - __old_size);
-    pointer __p =
-        __is_long() ? (__set_long_size(__n), __get_long_pointer()) : (__set_short_size(__n), __get_short_pointer());
+    pointer __p;
+    if (__is_long()) {
+      __set_long_size(__n);
+      __p = __get_long_pointer();
+    } else {
+      __set_short_size(__n);
+      __p = __get_short_pointer();
+    }
     traits_type::move(std::__to_address(__p), __s, __n);
     traits_type::assign(__p[__n], value_type());
     if (__old_size > __n)
@@ -2701,36 +2707,42 @@ template <class _CharT, class _Traits, class _Allocator>
 template <bool __is_short>
 _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_NOINLINE basic_string<_CharT, _Traits, _Allocator>&
 basic_string<_CharT, _Traits, _Allocator>::__assign_no_alias(const value_type* __s, size_type __n) {
-  size_type __cap      = capacity();
-  size_type __old_size = size();
-  if (__n <= __cap) {
-    if (__n > __old_size)
-      __annotate_increase(__n - __old_size);
-    pointer __p =
-        __is_short ? (__set_short_size(__n), __get_short_pointer()) : (__set_long_size(__n), __get_long_pointer());
+  const auto __cap = __is_short ? static_cast<size_type>(__min_cap) : __get_long_cap();
+  const auto __sz  = __is_short ? __get_short_size() : __get_long_size();
+  if (__n < __cap) {
+    if (__n > __sz)
+      __annotate_increase(__n - __sz);
+    pointer __p;
+    if (__is_short) {
+      __p = __get_short_pointer();
+      __set_short_size(__n);
+    } else {
+      __p = __get_long_pointer();
+      __set_long_size(__n);
+    }
     traits_type::copy(std::__to_address(__p), __s, __n);
     traits_type::assign(__p[__n], value_type());
-    if (__old_size > __n)
-      __annotate_shrink(__old_size);
+    if (__sz > __n)
+      __annotate_shrink(__sz);
   } else {
-    __grow_by_and_replace(__cap, __n - __cap, __old_size, 0, __old_size, __n, __s);
+    __grow_by_and_replace(__cap - 1, __n - __cap + 1, __sz, 0, __sz, __n, __s);
   }
   return *this;
 }
 
 template <class _CharT, class _Traits, class _Allocator>
 _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_NOINLINE basic_string<_CharT, _Traits, _Allocator>&
 basic_string<_CharT, _Traits, _Allocator>::__assign_external(const value_type* __s, size_type __n) {
-  size_type __cap      = capacity();
-  size_type __old_size = size();
+  const auto __cap = capacity();
+  const auto __sz  = size();
   if (__cap >= __n) {
-    if (__n > __old_size)
-      __annotate_increase(__n - __old_size);
+    if (__n > __sz)
+      __annotate_increase(__n - __sz);
     value_type* __p = std::__to_address(__get_pointer());
     traits_type::move(__p, __s, __n);
     return __null_terminate_at(__p, __n);
   } else {
-    __grow_by_and_replace(__cap, __n - __cap, __old_size, 0, __old_size, __n, __s);
+    __grow_by_and_replace(__cap, __n - __cap, __sz, 0, __sz, __n, __s);
     return *this;
   }
 }
@@ -2763,7 +2775,14 @@ basic_string<_CharT, _Traits, _Allocator>::operator=(value_type __c) {
   size_type __old_size = size();
   if (__old_size == 0)
     __annotate_increase(1);
-  pointer __p = __is_long() ? (__set_long_size(1), __get_long_pointer()) : (__set_short_size(1), __get_short_pointer());
+  pointer __p;
+  if (__is_long()) {
+    __set_long_size(1);
+    __p = __get_long_pointer();
+  } else {
+    __set_short_size(1);
+    __p = __get_short_pointer();
+  }
   traits_type::assign(*__p, __c);
   traits_type::assign(*++__p, value_type());
   if (__old_size > 1)
@@ -2947,10 +2966,8 @@ template <class _CharT, class _Traits, class _Allocator>
 _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string<_CharT, _Traits, _Allocator>&
 basic_string<_CharT, _Traits, _Allocator>::assign(const value_type* __s) {
   _LIBCPP_ASSERT_NON_NULL(__s != nullptr, "string::assign received nullptr");
-  if (__builtin_constant_p(*__s)) {
-    const size_type __n = traits_type::length(__s);
-    return __fits_in_sso(__n) ? __assign_short(__s, __n) : __assign_external(__s, __n);
-  }
+  if (auto __len = traits_type::length(__s); __builtin_constant_p(__len) && __fits_in_sso(__len))
+    return __assign_short(__s, __len);
   return __assign_external(__s);
 }
 // append
@@ -3026,8 +3043,14 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 void basic_string<_CharT, _Traits, _Allocator>::pu
     __is_short = false; // the string is always long after __grow_by
   }
   __annotate_increase(1);
-  pointer __p = __is_short ? (__set_short_size(__sz + 1), __get_short_pointer() + __sz)
-                           : (__set_long_size(__sz + 1), __get_long_pointer() + __sz);
+  pointer __p;
+  if (__is_short) {
+    __p = __get_short_pointer() + __sz;
+    __set_short_size(__sz + 1);
+  } else {
+    __p = __get_long_pointer() + __sz;
+    __set_long_size(__sz + 1);
+  }
   traits_type::assign(*__p, __c);
   traits_type::assign(*++__p, value_type());
 }
@@ -3468,9 +3491,9 @@ inline _LIBCPP_CONSTEXPR_SINCE_CXX20 void basic_string<_CharT, _Traits, _Allocat
   _LIBCPP_ASSERT_INTERNAL(__is_long(), "Trying to shrink small string");
 
   // We're a long string and we're shrinking into the small buffer.
-  auto __ptr  = __get_long_pointer();
-  auto __size = __get_long_size();
-  auto __cap  = __get_long_cap();
+  const auto __ptr  = __get_long_pointer();
+  const auto __size = __get_long_size();
+  const auto __cap  = __get_long_cap();
 
   if (__fits_in_sso(__target_capacity)) {
     __annotation_guard __g(*this);