You're seeing just the function not_lookahead, go back to Ergo.Combinators module for more information.
Link to this function

not_lookahead(parser, opts \\ [])

The not_lookahead parser accepts a parser and attempts to match it. If the match fails the not_lookahead parser returns status: :ok but does not affect the context otherwise.

If the match succeeds the not_lookahead parser fails with {:error, :lookahead_fail}


iex> alias Ergo.Context iex> import Ergo.{Combinators, Terminals} iex> parser = not_lookahead(literal("Foo")) iex> assert %Context{status: :ok, input: "Hello World"} = Ergo.parse(parser, "Hello World")

iex> alias Ergo.{Context, Parser} iex> import Ergo.{Combinators, Terminals} iex> parser = not_lookahead(literal("Hello")) iex> assert %Context{status: {:error, [{:lookahead_fail, "Satisfied: literal<Hello>"}]}, input: "Hello World"} = Ergo.parse(parser, "Hello World")