Error handling in Lexer

[Al]

tan/src/lexer/lexer.cpp

Lines 266 to 271 in b2cb68f

         // TODO error handling 
     } 
     _token_infos.emplace_back(t); 
 } else if (line[current] == '"') { // string literals 
     auto *t = 
         advance_for_string_literal(line, current, line_len); 

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This issue was generated by todo based on a TODO comment in b2cb68f when #2 was merged. cc @tjysdsg.