Replace ignore to compile_fail
//! A parser in nom is a function which, for an input type `I`, an output type `O`
//! and an optional error type `E`, will have the following signature:
//!
-//! ```rust,ignore
+//! ```rust,compile_fail
//! fn parser(input: I) -> IResult<I, O, E>;
//! ```
//!
//! Or like this, if you don't want to specify a custom error type (it will be `(I, ErrorKind)` by default):
//!
-//! ```rust,ignore
+//! ```rust,compile_fail
//! fn parser(input: I) -> IResult<I, O>;
//! ```
//!
