Move visited_cases in class scope

Rename visited_cases to visited_switch_cases_ and move it in class
scope. VisitSwitchStmt always resets the set of visited switch cases.

The old implementation was buggy because it saved reused SwitchCase
pointers across translation units, making contain() return true for
switches declared in other TUs.

Author: lucic71

cpp2rust/converter/converter.cpp

@@ -2579,13 +2579,11 @@ bool Converter::VisitImplicitValueInitExpr(clang::ImplicitValueInitExpr *expr) {
   return false;
 }
 
-static std::unordered_set<clang::SwitchCase *> visited_cases;
-
 bool Converter::VisitSwitchCase(clang::SwitchCase *stmt) {
-  if (visited_cases.contains(stmt)) {
+  if (visited_switch_cases_.contains(stmt)) {
     return false;
   }
-  visited_cases.insert(stmt);
+  visited_switch_cases_.insert(stmt);
 
   if (auto case_stmt = clang::dyn_cast<clang::CaseStmt>(stmt)) {
     Convert(case_stmt->getLHS());
@@ -2615,6 +2613,8 @@ bool Converter::VisitSwitchStmt(clang::SwitchStmt *stmt) {
   auto body = llvm::cast<clang::CompoundStmt>(stmt->getBody());
   assert(body);
 
+  visited_switch_cases_ = {};
+
   break_with_explicit_label_ = true;
   for (auto it = body->body_begin(), end = body->body_end(); it != end;) {
     if (auto switch_case = clang::dyn_cast<clang::SwitchCase>(*it)) {

cpp2rust/converter/converter.h

@@ -462,6 +462,7 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
   bool break_with_explicit_label_ = false;
   std::stack<clang::Expr *> curr_for_inc_;
   std::stack<clang::QualType> curr_init_type_;
+  std::unordered_set<clang::SwitchCase *> visited_switch_cases_;
 
   std::unordered_set<const clang::VarDecl *> map_iter_decls_;