chore: update to c++20 (#12117)

This PR upgrades Lean's internal toolchain to use C++20 as a preparatory
step for #12044.

Author: hargoniX

.github/workflows/ci.yml

@@ -260,7 +260,7 @@ jobs:
               {
                 "name": "Linux fsanitize",
                 // Always run on large if available, more reliable regarding timeouts
-                "os": large ? "nscloud-ubuntu-22.04-amd64-8x16-with-cache" : "ubuntu-latest",
+                "os": large ? "nscloud-ubuntu-22.04-amd64-16x32-with-cache" : "ubuntu-latest",
                 "enabled": level >= 2,
                 // do not fail nightlies on this for now
                 "secondary": level <= 2,
@@ -277,7 +277,7 @@ jobs:
                 // * `grind_guide` always times out.
                 // * `pkg/|lake/` tests sometimes time out (likely even hang), related to Lake CI
                 //   failures?
-                "CTEST_OPTIONS": "-E 'StackOverflow|reverse-ffi|interactive|async_select_channel|9366|run/bv_|grind_guide|pkg/|lake/'"
+                "CTEST_OPTIONS": "-E 'StackOverflow|reverse-ffi|interactive|async_select_channel|9366|run/bv_|grind_guide|grind_bitvec2|grind_constProp|grind_indexmap|grind_list|grind_lint|grind_array_attach|grind_ite_trace|pkg/|lake/'"
               },
               {
                 "name": "macOS",

flake.lock

@@ -18,7 +18,7 @@
       # An old nixpkgs for creating releases with an old glibc
       pkgsDist-old-aarch = import inputs.nixpkgs-old { localSystem.config = "aarch64-unknown-linux-gnu"; };
 
-      llvmPackages = pkgs.llvmPackages_15;
+      llvmPackages = pkgs.llvmPackages_19;
 
       devShellWithDist = pkgsDist: pkgs.mkShell.override {
           stdenv = pkgs.overrideCC pkgs.stdenv llvmPackages.clang;

flake.nix

@@ -250,7 +250,7 @@ else()
 endif()
 
 if(NOT MSVC)
-  set(CMAKE_CXX_FLAGS "-Wall -Wextra -std=c++14 ${CMAKE_CXX_FLAGS}")
+  set(CMAKE_CXX_FLAGS "-Wall -Wextra -std=c++20 ${CMAKE_CXX_FLAGS}")
   set(CMAKE_CXX_FLAGS_DEBUG "-g3 ${CMAKE_CXX_FLAGS_DEBUG}")
   if(CMAKE_SYSTEM_NAME MATCHES "Emscripten")
     # smallest+slower | -Oz .. -Os .. -O3 | largest+faster

src/CMakeLists.txt

@@ -57,7 +57,7 @@ void finalize_time_task() {
 time_task::time_task(std::string const & category, options const & opts, name decl) :
         m_category(category) {
     if (get_profiler(opts)) {
-        m_timeit = optional<xtimeit>(get_profiling_threshold(opts), [=](second_duration duration) mutable {
+        m_timeit = optional<xtimeit>(get_profiling_threshold(opts), [=, this](second_duration duration) mutable {
             sstream ss;
             ss << m_category;
             if (decl)

src/library/time_task.cpp

@@ -72,7 +72,7 @@ class buffer {
         m_buffer(reinterpret_cast<T *>(m_initial_buffer)),
         m_pos(0),
         m_capacity(INITIAL_SIZE) {
-        std::for_each(source.begin(), source.end(), [=](T const & e) { push_back(e); });
+        std::for_each(source.begin(), source.end(), [=, this](T const & e) { push_back(e); });
     }
 
     void ensure_capacity(size_t new_capacity) {
@@ -85,7 +85,7 @@ class buffer {
 
     buffer & operator=(buffer const & source) {
         clear();
-        std::for_each(source.begin(), source.end(), [=](T const & e) { push_back(e); });
+        std::for_each(source.begin(), source.end(), [=, this](T const & e) { push_back(e); });
         return *this;
     }
 

src/runtime/buffer.h

@@ -64,7 +64,7 @@ void check_interrupted() {
     if (g_cancel_tk) {
         inc_ref(g_cancel_tk);
         if (lean_io_cancel_token_is_set(g_cancel_tk) &&
-            !std::uncaught_exception()) {
+            !std::uncaught_exceptions()) {
             throw interrupted();
         }
     }

src/runtime/interrupt.cpp

@@ -125,7 +125,7 @@ list<T> append(list<T> const & l1, list<T> const & l2) {
 /** \brief Given list <tt>(a_0, ..., a_k)</tt>, return list <tt>(f(a_0), ..., f(a_k))</tt>. */
 template<typename To, typename From, typename F>
 list<To> map2(list<From> const & l, F && f) {
-    static_assert(std::is_same<typename std::result_of<F(From const &)>::type, To>::value,
+    static_assert(std::is_same<typename std::invoke_result<F(From const &)>::type, To>::value,
                   "map: return type of f is not equal to input type");
     if (is_nil(l)) {
         return list<To>();
@@ -271,7 +271,7 @@ list<T> map_reuse(list<T> const & l, F && f, Eq const & eq = Eq()) {
 /** \brief Given list <tt>(a_0, ..., a_k)</tt>, exec f(a_0); f(a_1); ... f(a_k)</tt>. */
 template<typename T, typename F>
 void for_each(list<T> const & l, F && f) {
-    static_assert(std::is_same<typename std::result_of<F(T const &)>::type, void>::value,
+    static_assert(std::is_same<typename std::invoke_result<F(T const &)>::type, void>::value,
                   "for_each: return type of f is not void");
     typedef typename list<T>::cell cell;
     cell * it = l.raw();
@@ -285,7 +285,7 @@ void for_each(list<T> const & l, F && f) {
     exec f(a_0, b_0); f(a_1, b_1); ... f(a_k, b_k)</tt>. */
 template<typename T1, typename T2, typename F>
 void for_each2(list<T1> const & l1, list<T2> const & l2, F && f) {
-    static_assert(std::is_same<typename std::result_of<F(T1 const &, T2 const &)>::type, void>::value,
+    static_assert(std::is_same<typename std::invoke_result<F(T1 const &, T2 const &)>::type, void>::value,
                   "for_each2: return type of f is not void");
     typedef typename list<T1>::cell cell1;
     typedef typename list<T2>::cell cell2;
@@ -303,7 +303,7 @@ void for_each2(list<T1> const & l1, list<T2> const & l2, F && f) {
     exec f(a_0, b_0, c_0); f(a_1, b_1, c_1); ... f(a_k, b_k, c_k)</tt>. */
 template<typename T1, typename T2, typename T3, typename F>
 void for_each3(list<T1> const & l1, list<T2> const & l2, list<T3> const & l3, F && f) {
-    static_assert(std::is_same<typename std::result_of<F(T1 const &, T2 const &, T3 const &)>::type, void>::value,
+    static_assert(std::is_same<typename std::invoke_result<F(T1 const &, T2 const &, T3 const &)>::type, void>::value,
                   "for_each2: return type of f is not void");
     typedef typename list<T1>::cell cell1;
     typedef typename list<T2>::cell cell2;
@@ -322,7 +322,7 @@ void for_each3(list<T1> const & l1, list<T2> const & l2, list<T3> const & l3, F
 /** \brief Compare two lists using the binary predicate p. */
 template<typename T, typename P>
 bool compare(list<T> const & l1, list<T> const & l2, P && p) {
-    static_assert(std::is_same<typename std::result_of<P(T const &, T const &)>::type, bool>::value,
+    static_assert(std::is_same<typename std::invoke_result<P(T const &, T const &)>::type, bool>::value,
                   "compare: return type of f is not bool");
     auto it1 = l1.begin();
     auto it2 = l2.begin();