lint: add more linters for using absl:: over std::

tools/code_format/check_format.py

@@ -698,6 +698,8 @@ def checkSourceLine(line, file_path, reportError):
     reportError("Don't use std::optional; use absl::optional instead")
   if tokenInLine("std::variant", line):
     reportError("Don't use std::variant; use absl::variant instead")
+  if tokenInLine("std::visit", line):
+    reportError("Don't use std::visit; use absl::visit instead")
   if "__attribute__((packed))" in line and file_path != "./include/envoy/common/platform.h":
     # __attribute__((packed)) is not supported by MSVC, we have a PACKED_STRUCT macro that
     # can be used instead

tools/code_format/check_format_test_helper.py

@@ -249,6 +249,7 @@ def runChecks():
                                 "Don't use std::optional; use absl::optional instead")
   errors += checkUnfixableError("std_variant.cc",
                                 "Don't use std::variant; use absl::variant instead")
+  errors += checkUnfixableError("std_visit.cc", "Don't use std::visit; use absl::visit instead")
   errors += checkUnfixableError(
       "throw.cc", "Don't introduce throws into exception-free files, use error statuses instead.")
   errors += checkFileExpectingOK("commented_throw.cc")

tools/testdata/check_format/std_visit.cc

@@ -0,0 +1,12 @@
+namespace Envoy {
+  struct SomeVisitorFunctor {
+      template<typename T>
+      void operator()(const T& i) const {}
+  };
+
+  void foo() {
+    absl::variant<int, std::string> foo = std::string("foo");
+    SomeVisitorFunctor visitor;
+    std::visit(visitor, foo);
+  }
+} // namespace Envoy