Update to Clang 10 and Visual Studio 2019 version 16.6p2

CMakeLists.txt

@@ -1,7 +1,7 @@
 # Copyright (c) Microsoft Corporation.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.16)
 set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
 project(msvc_standard_libraries LANGUAGES CXX)
 

README.md

@@ -140,7 +140,7 @@ Just try to follow these rules, so we can spend more time fixing bugs and implem
 The STL uses boost-math headers to provide P0226R1 Mathematical Special Functions. We recommend using [vcpkg][] to
 acquire this dependency.
 
-1. Install Visual Studio 2019 16.6 Preview 1 or later.
+1. Install Visual Studio 2019 16.6 Preview 2 or later.
 2. Invoke `git clone https://github.com/microsoft/vcpkg`
 3. Invoke `cd vcpkg`
 4. Invoke `.\bootstrap-vcpkg.bat`
@@ -159,7 +159,7 @@ acquire this dependency.
 These instructions assume you're targeting `x64-windows`; you can change this constant below to target other
 architectures.
 
-1. Install [CMake][] 3.16.5 or later, [Ninja][] 1.10.0 or later, and Visual Studio 2019 16.6 Preview 1 or later.
+1. Install [CMake][] 3.16.5 or later, [Ninja][] 1.10.0 or later, and Visual Studio 2019 16.6 Preview 2 or later.
 2. Invoke `git clone https://github.com/microsoft/vcpkg`
 3. Invoke `cd vcpkg`
 4. Invoke `.\bootstrap-vcpkg.bat`

azure-devops/create-new-agent-image.ps1

@@ -8,7 +8,7 @@
 
 $Location = 'westus2'
 $Prefix = 'StlBuild-' + (Get-Date -Format 'yyyy-MM-dd')
-$VMSize = 'Standard_D16s_v3'
+$VMSize = 'Standard_F16s_v2'
 $ProtoVMName = 'PROTOTYPE'
 $LiveVMPrefix = 'BUILD'
 $WindowsServerSku = '2019-Datacenter'
@@ -249,7 +249,7 @@ $VmssIpConfig = New-AzVmssIpConfig -SubnetId $Nic.IpConfigurations[0].Subnet.Id
 $VmssName = $ResourceGroupName + 'Vmss'
 $Vmss = New-AzVmssConfig `
   -Location $Location `
-  -SkuCapacity 2 `
+  -SkuCapacity 0 `
   -SkuName $VMSize `
   -SkuTier 'Standard' `
   -Overprovision $false `

azure-devops/provision-image.ps1

@@ -40,7 +40,7 @@ $ReleaseInPath = 'Preview'
 $Sku = 'Enterprise'
 $VisualStudioBootstrapperUrl = 'https://aka.ms/vs/16/pre/vs_buildtools.exe'
 $CMakeUrl = 'https://github.com/Kitware/CMake/releases/download/v3.16.5/cmake-3.16.5-win64-x64.msi'
-$LlvmUrl = 'https://releases.llvm.org/9.0.0/LLVM-9.0.0-win64.exe'
+$LlvmUrl = 'https://github.com/llvm/llvm-project/releases/download/llvmorg-10.0.0/LLVM-10.0.0-win64.exe'
 $NinjaUrl = 'https://github.com/ninja-build/ninja/releases/download/v1.10.0/ninja-win.zip'
 $PythonUrl = 'https://www.python.org/ftp/python/3.8.2/python-3.8.2-amd64.exe'
 
@@ -190,4 +190,13 @@ $environmentKey = Get-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control
 Set-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager\Environment' `
   -Name Path `
   -Value "$($environmentKey.Path);C:\Program Files\CMake\bin;C:\Program Files\LLVM\bin"
+
+Add-MPPreference -ExclusionPath C:\agent
+Add-MPPreference -ExclusionPath D:\
+Add-MPPreference -ExclusionProcess ninja.exe
+Add-MPPreference -ExclusionProcess clang-cl.exe
+Add-MPPreference -ExclusionProcess cl.exe
+Add-MPPreference -ExclusionProcess link.exe
+Add-MPPreference -ExclusionProcess python.exe
+
 C:\Windows\system32\sysprep\sysprep.exe /oobe /generalize /shutdown

azure-devops/run-build.yml

@@ -5,7 +5,7 @@ jobs:
 - job: ${{ parameters.targetPlatform }}
   timeoutInMinutes: 360
   pool:
-    name: StlBuild-2020-03-24
+    name: StlBuild-2020-03-28
 
   variables:
     vcpkgLocation: '$(Build.SourcesDirectory)/vcpkg'

stl/inc/algorithm

@@ -1249,8 +1249,8 @@ _FwdIt2 copy_if(_ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _FwdIt2 _Dest, _Pr _Pred
 #if _ITERATOR_DEBUG_ARRAY_OVERLOADS
 template <class _ExPo, class _FwdIt1, class _DestTy, size_t _DestSize, class _Pr,
     _Enable_if_execution_policy_t<_ExPo> = 0>
-_DestTy* copy_if(
-    _ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _DestTy (&_Dest)[_DestSize], _Pr _Pred) noexcept /* terminates */ {
+_DestTy* copy_if(_ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _DestTy (&_Dest)[_DestSize], _Pr _Pred) noexcept
+/* terminates */ {
     // copy each satisfying _Pred, array dest
     // not parallelized at present, parallelism expected to be feasible in a future release
     _REQUIRE_PARALLEL_ITERATOR(_FwdIt1);
@@ -1397,8 +1397,8 @@ pair<_FwdIt2, _DestFalseTy*> partition_copy(_ExPo&&, _FwdIt1 _First, _FwdIt1 _La
 template <class _ExPo, class _FwdIt1, class _DestTrueTy, size_t _DestTrueSize, class _DestFalseTy,
     size_t _DestFalseSize, class _Pr, _Enable_if_execution_policy_t<_ExPo> = 0>
 pair<_DestTrueTy*, _DestFalseTy*> partition_copy(_ExPo&&, _FwdIt1 _First, _FwdIt1 _Last,
-    _DestTrueTy (&_Dest_true)[_DestTrueSize], _DestFalseTy (&_Dest_false)[_DestFalseSize],
-    _Pr _Pred) noexcept /* terminates */ {
+    _DestTrueTy (&_Dest_true)[_DestTrueSize], _DestFalseTy (&_Dest_false)[_DestFalseSize], _Pr _Pred) noexcept
+/* terminates */ {
     // copy true partition to _Dest_true, false to _Dest_false, array dest
     // not parallelized at present, parallelism expected to be feasible in a future release
     _REQUIRE_PARALLEL_ITERATOR(_FwdIt1);
@@ -2005,8 +2005,8 @@ _NODISCARD _FwdIt1 find_end(
     _ExPo&& _Exec, _FwdIt1 _First1, _FwdIt1 _Last1, _FwdIt2 _First2, _FwdIt2 _Last2, _Pr _Pred) noexcept; // terminates
 
 template <class _ExPo, class _FwdIt1, class _FwdIt2, _Enable_if_execution_policy_t<_ExPo> = 0>
-_NODISCARD _FwdIt1 find_end(_ExPo&& _Exec, _FwdIt1 _First1, _FwdIt1 _Last1, _FwdIt2 _First2,
-    _FwdIt2 _Last2) noexcept /* terminates */ { // find last [_First2, _Last2) match
+_NODISCARD _FwdIt1 find_end(_ExPo&& _Exec, _FwdIt1 _First1, _FwdIt1 _Last1, _FwdIt2 _First2, _FwdIt2 _Last2) noexcept
+/* terminates */ { // find last [_First2, _Last2) match
     return _STD find_end(_STD forward<_ExPo>(_Exec), _First1, _Last1, _First2, _Last2, equal_to<>());
 }
 #endif // _HAS_CXX17
@@ -2123,8 +2123,8 @@ _FwdIt2 transform(
 #if _ITERATOR_DEBUG_ARRAY_OVERLOADS
 template <class _ExPo, class _FwdIt1, class _DestTy, size_t _DestSize, class _Fn,
     _Enable_if_execution_policy_t<_ExPo> = 0>
-_DestTy* transform(
-    _ExPo&& _Exec, _FwdIt1 _First, _FwdIt1 _Last, _DestTy (&_Dest)[_DestSize], _Fn _Func) noexcept /* terminates */ {
+_DestTy* transform(_ExPo&& _Exec, _FwdIt1 _First, _FwdIt1 _Last, _DestTy (&_Dest)[_DestSize], _Fn _Func) noexcept
+/* terminates */ {
     // transform [_First, _Last) with _Func, array dest
     return _STD transform(
         _STD forward<_ExPo>(_Exec), _First, _Last, _Array_iterator<_DestTy, _DestSize>(_Dest), _Pass_fn(_Func))
@@ -2338,8 +2338,8 @@ _CONSTEXPR20 _DestTy* replace_copy_if(
 
 #if _HAS_CXX17
 template <class _ExPo, class _FwdIt1, class _FwdIt2, class _Pr, class _Ty, _Enable_if_execution_policy_t<_ExPo> = 0>
-_FwdIt2 replace_copy_if(
-    _ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _FwdIt2 _Dest, _Pr _Pred, const _Ty& _Val) noexcept /* terminates */ {
+_FwdIt2 replace_copy_if(_ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _FwdIt2 _Dest, _Pr _Pred, const _Ty& _Val) noexcept
+/* terminates */ {
     // copy replacing each satisfying _Pred with _Val
     // not parallelized at present, parallelism expected to be feasible in a future release
     _REQUIRE_PARALLEL_ITERATOR(_FwdIt1);
@@ -2474,8 +2474,8 @@ _FwdIt2 remove_copy(_ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _FwdIt2 _Dest, const
 #if _ITERATOR_DEBUG_ARRAY_OVERLOADS
 template <class _ExPo, class _FwdIt1, class _DestTy, size_t _DestSize, class _Ty,
     _Enable_if_execution_policy_t<_ExPo> = 0>
-_DestTy* remove_copy(
-    _ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _DestTy (&_Dest)[_DestSize], const _Ty& _Val) noexcept /* terminates */ {
+_DestTy* remove_copy(_ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _DestTy (&_Dest)[_DestSize], const _Ty& _Val) noexcept
+/* terminates */ {
     // copy omitting each matching _Val, array dest
     // not parallelized at present, parallelism expected to be feasible in a future release
     _REQUIRE_PARALLEL_ITERATOR(_FwdIt1);
@@ -2524,8 +2524,8 @@ _FwdIt2 remove_copy_if(_ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _FwdIt2 _Dest, _P
 #if _ITERATOR_DEBUG_ARRAY_OVERLOADS
 template <class _ExPo, class _FwdIt1, class _DestTy, size_t _DestSize, class _Pr,
     _Enable_if_execution_policy_t<_ExPo> = 0>
-_DestTy* remove_copy_if(
-    _ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _DestTy (&_Dest)[_DestSize], _Pr _Pred) noexcept /* terminates */ {
+_DestTy* remove_copy_if(_ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _DestTy (&_Dest)[_DestSize], _Pr _Pred) noexcept
+/* terminates */ {
     // copy omitting each element satisfying _Pred, array dest
     // not parallelized at present, parallelism expected to be feasible in a future release
     _REQUIRE_PARALLEL_ITERATOR(_FwdIt1);
@@ -2772,8 +2772,8 @@ _FwdIt2 unique_copy(_ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _FwdIt2 _Dest, _Pr _
 #if _ITERATOR_DEBUG_ARRAY_OVERLOADS
 template <class _ExPo, class _FwdIt1, class _DestTy, size_t _DestSize, class _Pr,
     _Enable_if_execution_policy_t<_ExPo> = 0>
-_DestTy* unique_copy(
-    _ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _DestTy (&_Dest)[_DestSize], _Pr _Pred) noexcept /* terminates */ {
+_DestTy* unique_copy(_ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _DestTy (&_Dest)[_DestSize], _Pr _Pred) noexcept
+/* terminates */ {
     // copy compressing pairs that match, array dest
     // not parallelized at present, parallelism expected to be feasible in a future release
     _REQUIRE_PARALLEL_ITERATOR(_FwdIt1);
@@ -3866,8 +3866,8 @@ _DestTy* merge(_ExPo&&, _FwdIt1 _First1, _FwdIt1 _Last1, _FwdIt2 _First2, _FwdIt
 #endif // _ITERATOR_DEBUG_ARRAY_OVERLOADS
 
 template <class _ExPo, class _FwdIt1, class _FwdIt2, class _FwdIt3, _Enable_if_execution_policy_t<_ExPo> = 0>
-_FwdIt3 merge(_ExPo&&, _FwdIt1 _First1, _FwdIt1 _Last1, _FwdIt2 _First2, _FwdIt2 _Last2,
-    _FwdIt3 _Dest) noexcept /* terminates */ {
+_FwdIt3 merge(_ExPo&&, _FwdIt1 _First1, _FwdIt1 _Last1, _FwdIt2 _First2, _FwdIt2 _Last2, _FwdIt3 _Dest) noexcept
+/* terminates */ {
     // copy merging ranges, both using operator<
     // not parallelized at present, parallelism expected to be feasible in a future release
     _REQUIRE_PARALLEL_ITERATOR(_FwdIt1);
@@ -4614,17 +4614,17 @@ _CONSTEXPR20 _RanIt partial_sort_copy(_InIt _First1, _InIt _Last1, _RanIt _First
 
 #if _HAS_CXX17
 template <class _ExPo, class _FwdIt, class _RanIt, class _Pr, _Enable_if_execution_policy_t<_ExPo> = 0>
-_RanIt partial_sort_copy(
-    _ExPo&&, _FwdIt _First1, _FwdIt _Last1, _RanIt _First2, _RanIt _Last2, _Pr _Pred) noexcept /* terminates */ {
+_RanIt partial_sort_copy(_ExPo&&, _FwdIt _First1, _FwdIt _Last1, _RanIt _First2, _RanIt _Last2, _Pr _Pred) noexcept
+/* terminates */ {
     // copy [_First1, _Last1) into [_First2, _Last2) using _Pred
     // parallelism suspected to be infeasible
     _REQUIRE_PARALLEL_ITERATOR(_FwdIt);
     return _STD partial_sort_copy(_First1, _Last1, _First2, _Last2, _Pass_fn(_Pred));
 }
 
 template <class _ExPo, class _FwdIt, class _RanIt, _Enable_if_execution_policy_t<_ExPo> = 0>
-_RanIt partial_sort_copy(
-    _ExPo&&, _FwdIt _First1, _FwdIt _Last1, _RanIt _First2, _RanIt _Last2) noexcept /* terminates */ {
+_RanIt partial_sort_copy(_ExPo&&, _FwdIt _First1, _FwdIt _Last1, _RanIt _First2, _RanIt _Last2) noexcept
+/* terminates */ {
     // copy [_First1, _Last1) into [_First2, _Last2), using operator<
     // parallelism suspected to be infeasible
     _REQUIRE_PARALLEL_ITERATOR(_FwdIt);
@@ -4715,8 +4715,8 @@ _NODISCARD _CONSTEXPR20 bool includes(_InIt1 _First1, _InIt1 _Last1, _InIt2 _Fir
 #if _HAS_CXX17
 // FUNCTION TEMPLATE includes
 template <class _ExPo, class _FwdIt1, class _FwdIt2, class _Pr, _Enable_if_execution_policy_t<_ExPo> = 0>
-_NODISCARD bool includes(
-    _ExPo&&, _FwdIt1 _First1, _FwdIt1 _Last1, _FwdIt2 _First2, _FwdIt2 _Last2, _Pr _Pred) noexcept /* terminates */ {
+_NODISCARD bool includes(_ExPo&&, _FwdIt1 _First1, _FwdIt1 _Last1, _FwdIt2 _First2, _FwdIt2 _Last2, _Pr _Pred) noexcept
+/* terminates */ {
     // test if every element in sorted [_First2, _Last2) is in sorted [_First1, _Last1), using _Pred
     // not parallelized at present, parallelism expected to be feasible in a future release
     _REQUIRE_PARALLEL_ITERATOR(_FwdIt1);
@@ -4725,8 +4725,8 @@ _NODISCARD bool includes(
 }
 
 template <class _ExPo, class _FwdIt1, class _FwdIt2, _Enable_if_execution_policy_t<_ExPo> = 0>
-_NODISCARD bool includes(
-    _ExPo&&, _FwdIt1 _First1, _FwdIt1 _Last1, _FwdIt2 _First2, _FwdIt2 _Last2) noexcept /* terminates */ {
+_NODISCARD bool includes(_ExPo&&, _FwdIt1 _First1, _FwdIt1 _Last1, _FwdIt2 _First2, _FwdIt2 _Last2) noexcept
+/* terminates */ {
     // test if every element in sorted [_First2, _Last2) is in sorted [_First1, _Last1), using operator<
     // not parallelized at present, parallelism expected to be feasible in a future release
     _REQUIRE_PARALLEL_ITERATOR(_FwdIt1);
@@ -4818,8 +4818,8 @@ _DestTy* set_union(_ExPo&&, _FwdIt1 _First1, _FwdIt1 _Last1, _FwdIt2 _First2, _F
 #endif // _ITERATOR_DEBUG_ARRAY_OVERLOADS
 
 template <class _ExPo, class _FwdIt1, class _FwdIt2, class _FwdIt3, _Enable_if_execution_policy_t<_ExPo> = 0>
-_FwdIt3 set_union(_ExPo&&, _FwdIt1 _First1, _FwdIt1 _Last1, _FwdIt2 _First2, _FwdIt2 _Last2,
-    _FwdIt3 _Dest) noexcept /* terminates */ {
+_FwdIt3 set_union(_ExPo&&, _FwdIt1 _First1, _FwdIt1 _Last1, _FwdIt2 _First2, _FwdIt2 _Last2, _FwdIt3 _Dest) noexcept
+/* terminates */ {
     // OR sets [_First1, _Last1) and [_First2, _Last2), using operator<
     // not parallelized at present, parallelism expected to be feasible in a future release
     _REQUIRE_PARALLEL_ITERATOR(_FwdIt1);
@@ -5281,8 +5281,8 @@ _NODISCARD constexpr pair<_FwdIt, _FwdIt> minmax_element(_FwdIt _First, _FwdIt _
 
 #if _HAS_CXX17
 template <class _ExPo, class _FwdIt, class _Pr, _Enable_if_execution_policy_t<_ExPo> = 0>
-_NODISCARD pair<_FwdIt, _FwdIt> minmax_element(
-    _ExPo&&, _FwdIt _First, _FwdIt _Last, _Pr _Pred) noexcept /* terminates */ {
+_NODISCARD pair<_FwdIt, _FwdIt> minmax_element(_ExPo&&, _FwdIt _First, _FwdIt _Last, _Pr _Pred) noexcept
+/* terminates */ {
     // find smallest and largest elements, using _Pred
     // not parallelized at present, parallelism expected to be feasible in a future release
     return _STD minmax_element(_First, _Last, _Pass_fn(_Pred));

stl/inc/array

@@ -150,8 +150,8 @@ public:
         return _Elems[_Pos];
     }
 
-    _NODISCARD constexpr const_reference operator[](_In_range_(0, _Size - 1) size_type _Pos) const
-        noexcept /* strengthened */ {
+    _NODISCARD constexpr const_reference operator[](_In_range_(0, _Size - 1) size_type _Pos) const noexcept
+    /* strengthened */ {
 #if _CONTAINER_DEBUG_LEVEL > 0
         _STL_VERIFY(_Pos < _Size, "array subscript out of range");
 #endif // _CONTAINER_DEBUG_LEVEL > 0
@@ -200,7 +200,7 @@ struct _Enforce_same {
 };
 
 template <class _First, class... _Rest>
-array(_First, _Rest...)->array<typename _Enforce_same<_First, _Rest...>::type, 1 + sizeof...(_Rest)>;
+array(_First, _Rest...) -> array<typename _Enforce_same<_First, _Rest...>::type, 1 + sizeof...(_Rest)>;
 #endif // _HAS_CXX17
 
 template <class _Ty>

stl/inc/atomic

@@ -1637,7 +1637,7 @@ public:
 
 #if _HAS_CXX17
 template <class _Ty>
-atomic(_Ty)->atomic<_Ty>;
+atomic(_Ty) -> atomic<_Ty>;
 #endif // _HAS_CXX17
 
 // NONMEMBER OPERATIONS ON ATOMIC TYPES

stl/inc/bitset

@@ -286,23 +286,18 @@ public:
         constexpr bool _Bits_zero  = _Bits == 0;
         constexpr bool _Bits_small = _Bits <= 32;
         constexpr bool _Bits_large = _Bits > 64;
-        if
-            _CONSTEXPR_IF(_Bits_zero) {
-                return 0;
-            }
-        else if
-            _CONSTEXPR_IF(_Bits_small) {
-                return static_cast<unsigned long>(_Array[0]);
-            }
-        else {
-            if
-                _CONSTEXPR_IF(_Bits_large) {
-                    for (size_t _Idx = 1; _Idx <= _Words; ++_Idx) {
-                        if (_Array[_Idx] != 0) {
-                            _Xoflo(); // fail if any high-order words are nonzero
-                        }
+        if _CONSTEXPR_IF (_Bits_zero) {
+            return 0;
+        } else if _CONSTEXPR_IF (_Bits_small) {
+            return static_cast<unsigned long>(_Array[0]);
+        } else {
+            if _CONSTEXPR_IF (_Bits_large) {
+                for (size_t _Idx = 1; _Idx <= _Words; ++_Idx) {
+                    if (_Array[_Idx] != 0) {
+                        _Xoflo(); // fail if any high-order words are nonzero
                     }
                 }
+            }
 
             if (_Array[0] > ULONG_MAX) {
                 _Xoflo();
@@ -315,19 +310,16 @@ public:
     _NODISCARD unsigned long long to_ullong() const {
         constexpr bool _Bits_zero  = _Bits == 0;
         constexpr bool _Bits_large = _Bits > 64;
-        if
-            _CONSTEXPR_IF(_Bits_zero) {
-                return 0;
-            }
-        else {
-            if
-                _CONSTEXPR_IF(_Bits_large) {
-                    for (size_t _Idx = 1; _Idx <= _Words; ++_Idx) {
-                        if (_Array[_Idx] != 0) {
-                            _Xoflo(); // fail if any high-order words are nonzero
-                        }
+        if _CONSTEXPR_IF (_Bits_zero) {
+            return 0;
+        } else {
+            if _CONSTEXPR_IF (_Bits_large) {
+                for (size_t _Idx = 1; _Idx <= _Words; ++_Idx) {
+                    if (_Array[_Idx] != 0) {
+                        _Xoflo(); // fail if any high-order words are nonzero
                     }
                 }
+            }
 
             return _Array[0];
         }
@@ -431,10 +423,9 @@ private:
 
     void _Trim() noexcept { // clear any trailing bits in last word
         constexpr bool _Work_to_do = _Bits == 0 || _Bits % _Bitsperword != 0;
-        if
-            _CONSTEXPR_IF(_Work_to_do) {
-                _Array[_Words] &= (_Ty{1} << _Bits % _Bitsperword) - 1;
-            }
+        if _CONSTEXPR_IF (_Work_to_do) {
+            _Array[_Words] &= (_Ty{1} << _Bits % _Bitsperword) - 1;
+        }
     }
 
     bitset& _Set_unchecked(size_t _Pos, bool _Val) noexcept { // set bit at _Pos to _Val, no checking
@@ -534,12 +525,11 @@ basic_istream<_Elem, _Tr>& operator>>(basic_istream<_Elem, _Tr>& _Istr, bitset<_
 
     constexpr bool _Has_bits = _Bits > 0;
 
-    if
-        _CONSTEXPR_IF(_Has_bits) {
-            if (!_Changed) {
-                _State |= _Istr_t::failbit;
-            }
+    if _CONSTEXPR_IF (_Has_bits) {
+        if (!_Changed) {
+            _State |= _Istr_t::failbit;
         }
+    }
 
     _Istr.setstate(_State);
     _Right = bitset<_Bits>(_Str); // convert string and store