main.cpp: In function 'int main()':
main.cpp:58:24: error: 'BfsVisitor' was not declared in this scope
   static_assert(sizeof(BfsVisitor<char>) <= 2*sizeof(char*));
                        ^~~~~~~~~~
main.cpp:58:35: error: expected primary-expression before 'char'
   static_assert(sizeof(BfsVisitor<char>) <= 2*sizeof(char*));
                                   ^~~~
main.cpp:58:35: error: expected ')' before 'char'
main.cpp:58:61: error: expected ',' before ';' token
   static_assert(sizeof(BfsVisitor<char>) <= 2*sizeof(char*));
                                                             ^
main.cpp:58:61: error: expected string-literal before ';' token
main.cpp:58:61: error: expected ')' before ';' token
main.cpp:63:16: error: expected primary-expression before 'int'
     BfsVisitor<int> visitor;
                ^~~
main.cpp:64:34: error: 'visitor' was not declared in this scope
     BreadthFirstSearch(graph, 0, visitor);
                                  ^~~~~~~
main.cpp:81:16: error: expected primary-expression before 'int'
     BfsVisitor<int> visitor;
                ^~~
main.cpp:82:34: error: 'visitor' was not declared in this scope
     BreadthFirstSearch(graph, 0, visitor);
                                  ^~~~~~~
main.cpp:114:16: error: expected primary-expression before 'int'
     BfsVisitor<int> visitor;
                ^~~
main.cpp:115:34: error: 'visitor' was not declared in this scope
     BreadthFirstSearch(graph, 0, visitor);
                                  ^~~~~~~