Inferring the regex pattern from terminals

If a token type should only produce terminals with known literal values (for example, a set of keywords), regex can be omitted since it can be inferred from the terminals.

use teleparse::prelude::*;

#[derive_lexicon]
#[teleparse(terminal_parse)]
pub enum MyToken {
    #[teleparse(terminal(Pizza = "pizza", Pasta = "pasta"))]
    Food,
}

fn main() {}

This is the Don't-Repeat-Yourself (DRY) principle. In fact, derive_lexicon enforces it:

use teleparse::prelude::*;

#[derive_lexicon]
pub enum TokenType {
    #[teleparse(terminal(
        OpAdd = "+", 
        OpSub = "-", 
        OpMul = "*", 
        OpDiv = "/",
    ), regex(r"[\+\-\*/]"))]
    Operator,
}

fn main() {}

error: Defining `regex` here is redundant because all terminals have a literal match pattern, so the rule can already be inferred.
  --> tests/ui/lex_redundant_regex.rs:11:5
   |
11 |     Operator,
   |     ^^^^^^^^