In some areas of the world (VHDL/Ada), you have to maintain symbol table for correct lexing.

These languages have constructions like OBJECT_NAME'ATTRIBUTE (object name can be anything with visible name in the scope and attributes depend on its kind) and RECORD_TYPE_NAME'SLICE where we create value of RECORD_TYPE_NAME using slice, which is collection of values of record fields.

There are also character literals, which have form like 'a', '1', '#', ''''. Just as you can expect here.

The combination of record value construction and lexer forms for character literals makes it hard to parse something like MY_RECORD'('1','0',false, 10).

Symbol table and/or dynamic parse construction allows you to parse these texts easily and specify the syntax straightforwardly. The other approach with construction of separate AST complicates things a lot.