Fix compilation under and enable C++20 (#12658)

This commit enables `/std:c++20` for local development under VS17.
Our CIs will continue to use VS16 and C++17 for now in order to reduce
the likelihood of regressions during the current development cycle.
It's expected that we'll migrate to VS17 soon, as this
is what conhost is already being built with anyways.

## PR Checklist
* [x] Closes #12510
* [x] I work here
* [x] Tests added/passed

## Validation Steps Performed
* Everything compiles under `/std:c++20` ✅

dep/CLI11/README.md

@@ -1,5 +1,4 @@
 # CLI11
 
-Taken from [release v1.9.0](https://github.com/CLIUtils/CLI11/releases/tag/v1.9.0), source commit
-[dd0d8e4](https://github.com/CLIUtils/CLI11/commit/dd0d8e4fe729e5b1110232c7a5c9566dad884686)
-
+Taken from [release v1.9.1](https://github.com/CLIUtils/CLI11/releases/tag/v1.9.1), source commit
+[5cb3efa](https://github.com/CLIUtils/CLI11/commit/5cb3efabce007c3a0230e4cc2e27da491c646b6c)

src/cascadia/LocalTests_SettingsModel/ColorSchemeTests.cpp

@@ -84,7 +84,7 @@ namespace SettingsModelLocalTests
 
         for (size_t i = 0; i < expectedCampbellTable.size(); i++)
         {
-            const auto& expected = expectedCampbellTable.at(i);
+            const til::color expected{ expectedCampbellTable.at(i) };
             const til::color actual{ scheme->Table().at(static_cast<uint32_t>(i)) };
             VERIFY_ARE_EQUAL(expected, actual);
         }

src/cascadia/LocalTests_SettingsModel/TerminalSettingsTests.cpp

@@ -795,11 +795,11 @@ namespace SettingsModelLocalTests
         const auto terminalSettings4 = createTerminalSettings(activeProfiles.GetAt(4), colorSchemes);
         const auto terminalSettings5 = createTerminalSettings(activeProfiles.GetAt(5), colorSchemes);
 
-        VERIFY_ARE_EQUAL(RGB(0x12, 0x34, 0x56), terminalSettings0->CursorColor()); // from color scheme
+        VERIFY_ARE_EQUAL(til::color(0x12, 0x34, 0x56), terminalSettings0->CursorColor()); // from color scheme
         VERIFY_ARE_EQUAL(DEFAULT_CURSOR_COLOR, terminalSettings1->CursorColor()); // default
-        VERIFY_ARE_EQUAL(RGB(0x23, 0x45, 0x67), terminalSettings2->CursorColor()); // from profile (trumps color scheme)
-        VERIFY_ARE_EQUAL(RGB(0x34, 0x56, 0x78), terminalSettings3->CursorColor()); // from profile (not set in color scheme)
-        VERIFY_ARE_EQUAL(RGB(0x45, 0x67, 0x89), terminalSettings4->CursorColor()); // from profile (no color scheme)
+        VERIFY_ARE_EQUAL(til::color(0x23, 0x45, 0x67), terminalSettings2->CursorColor()); // from profile (trumps color scheme)
+        VERIFY_ARE_EQUAL(til::color(0x34, 0x56, 0x78), terminalSettings3->CursorColor()); // from profile (not set in color scheme)
+        VERIFY_ARE_EQUAL(til::color(0x45, 0x67, 0x89), terminalSettings4->CursorColor()); // from profile (no color scheme)
         VERIFY_ARE_EQUAL(DEFAULT_CURSOR_COLOR, terminalSettings5->CursorColor()); // default
     }
 

src/cascadia/TerminalApp/AppLogic.cpp

@@ -1007,7 +1007,7 @@ namespace winrt::TerminalApp::implementation
         const auto package{ GetCurrentPackageNoThrow() };
         if (package == nullptr)
         {
-            return;
+            co_return;
         }
 
         const auto tryEnableStartupTask = _settings.GlobalSettings().StartOnUserLogin();

src/cascadia/TerminalApp/TabBase.cpp

@@ -176,7 +176,7 @@ namespace winrt::TerminalApp::implementation
 
         if (_keyChord == keyChordText)
         {
-            return;
+            co_return;
         }
 
         _keyChord = keyChordText;

src/cascadia/TerminalApp/TerminalTab.cpp

@@ -274,7 +274,7 @@ namespace winrt::TerminalApp::implementation
         // Don't reload our icon if it hasn't changed.
         if (iconPath == _lastIconPath)
         {
-            return;
+            co_return;
         }
 
         _lastIconPath = iconPath;
@@ -283,7 +283,7 @@ namespace winrt::TerminalApp::implementation
         // for when we show the icon again)
         if (_iconHidden)
         {
-            return;
+            co_return;
         }
 
         auto weakThis{ get_weak() };

src/cascadia/TerminalControl/TermControl.cpp

@@ -2274,7 +2274,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
     {
         if (_IsClosing())
         {
-            return;
+            co_return;
         }
 
         if (e.DataView().Contains(StandardDataFormats::ApplicationLink()))

src/cascadia/TerminalSettingsModel/FileUtils.cpp

@@ -12,7 +12,7 @@
 #include <sddl.h>
 #include <wil/token_helpers.h>
 
-static constexpr std::string_view Utf8Bom{ u8"\uFEFF" };
+static constexpr std::string_view Utf8Bom{ "\xEF\xBB\xBF", 3 };
 static constexpr std::wstring_view UnpackagedSettingsFolderName{ L"Microsoft\\Windows Terminal\\" };
 
 namespace winrt::Microsoft::Terminal::Settings::Model

src/common.build.pre.props

@@ -118,7 +118,8 @@
       <RuntimeTypeInfo>false</RuntimeTypeInfo>
       <ConformanceMode>true</ConformanceMode>
       <UseStandardPreprocessor>true</UseStandardPreprocessor>
-      <LanguageStandard>stdcpp17</LanguageStandard>
+      <LanguageStandard Condition="$(MSBuildVersion) &lt; '17.0.0'">stdcpp17</LanguageStandard>
+      <LanguageStandard Condition="$(MSBuildVersion) &gt;= '17.0.0'">stdcpp20</LanguageStandard>
       <LanguageStandard_C>stdc17</LanguageStandard_C>
       <AdditionalOptions>%(AdditionalOptions) /utf-8 /Zc:externConstexpr /Zc:lambda /Zc:throwingNew</AdditionalOptions>
       <ControlFlowGuard>Guard</ControlFlowGuard>

src/host/ft_host/InitTests.cpp

@@ -25,7 +25,7 @@ static FILE* std_in = nullptr;
 // This will automatically try to terminate the job object (and all of the
 // binaries under test that are children) whenever this class gets shut down.
 // also closes the FILE pointers created by reopening stdin and stdout.
-auto OnAppExitKillJob = wil::scope_exit([&] {
+auto OnAppExitKillJob = wil::scope_exit([] {
     if (std_out != nullptr)
     {
         fclose(std_out);

src/inc/til/bit.h

@@ -8,9 +8,7 @@ namespace til
     template<class To, class From, std::enable_if_t<std::conjunction_v<std::bool_constant<sizeof(To) == sizeof(From)>, std::is_trivially_copyable<To>, std::is_trivially_copyable<From>>, int> = 0>
     [[nodiscard]] constexpr To bit_cast(const From& _Val) noexcept
     {
-#ifdef __cpp_lib_bit_cast
-#warning "Replace til::bit_cast and __builtin_bit_cast with std::bit_cast"
-#endif
+        // TODO: Replace til::bit_cast and __builtin_bit_cast with std::bit_cast
         return __builtin_bit_cast(To, _Val);
     }
 }

src/inc/til/enumset.h

@@ -124,13 +124,14 @@ namespace til // Terminal Implementation Library. Also: "Today I Learned"
         template<typename... Args>
         static constexpr UnderlyingType to_underlying(Args... positions) noexcept
         {
-            return ((UnderlyingType{ 1 } << static_cast<UnderlyingType>(positions)) | ...);
-        }
-
-        template<>
-        static constexpr UnderlyingType to_underlying() noexcept
-        {
-            return 0;
+            if constexpr (sizeof...(positions) == 0)
+            {
+                return 0;
+            }
+            else
+            {
+                return ((UnderlyingType{ 1 } << static_cast<UnderlyingType>(positions)) | ...);
+            }
         }
 
         UnderlyingType _data{};

src/terminal/parser/ft_fuzzer/fuzzing_directed.h

@@ -253,25 +253,27 @@ namespace fuzz
         template<class _Type>
         static _Type GetRandom(__in _Type tMin, __in _Type tMax)
         {
-            std::mt19937 engine(m_rd()); // Mersenne twister MT19937
-            std::uniform_int_distribution<_Type> distribution(tMin, tMax);
-            auto generator = std::bind(distribution, engine);
-            return generator();
+            if constexpr (std::is_same_v<_Type, BYTE>)
+            {
+                // uniform_int_distribution only works with _Is_IntType types, which do not
+                // currently include char or unsigned char, so here is a specialization
+                // specifically for BYTE (unsigned char).
+                std::mt19937 engine(m_rd()); // Mersenne twister MT19937
+                // BYTE is unsigned, so we want to also use an unsigned type to avoid sign
+                // extension of tMin and tMax.
+                std::uniform_int_distribution<unsigned short> distribution(tMin, tMax);
+                auto generator = std::bind(distribution, engine);
+                return static_cast<BYTE>(generator());
+            }
+            else
+            {
+                std::mt19937 engine(m_rd()); // Mersenne twister MT19937
+                std::uniform_int_distribution<_Type> distribution(tMin, tMax);
+                auto generator = std::bind(distribution, engine);
+                return generator();
+            }
         }
 
-        // uniform_int_distribution only works with _Is_IntType types, which do not
-        // currently include char or unsigned char, so here is a specialization
-        // specifically for BYTE (unsigned char).
-        template<>
-        static BYTE GetRandom(__in BYTE tMin, __in BYTE tMax)
-        {
-            std::mt19937 engine(m_rd()); // Mersenne twister MT19937
-            // BYTE is unsigned, so we want to also use an unsigned type to avoid sign
-            // extension of tMin and tMax.
-            std::uniform_int_distribution<unsigned short> distribution(tMin, tMax);
-            auto generator = std::bind(distribution, engine);
-            return static_cast<BYTE>(generator());
-        }
 #ifdef __min_collision__
 #undef __min_collision__
 #define min(a, b) (((a) < (b)) ? (a) : (b))