I'm trying to write a parser with pom, which is great - no problems writing the parsers and feeding in string literal as test data. However, when I try to run it bytes from a file, it chokes;
108 | fn parse_files() -> Result<(), Box<dyn Error>> {
109 | let byte_vec: Vec<u8> = std::fs::read("assets/valid_so_far.idl")?;
110 | let byte_slice: &[u8] = &byte_vec;
| ^^^^^^^^^ borrowed value does not live long enough
111 | let idl_parser = idl();
112 | let parse_result = idl_parser.parse(byte_slice)?;
| ---------------------------- argument requires that `byte_vec` is borrowed for `'static`
113 |
114 | Ok(())
115 | }
| - `byte_vec` dropped here while still borrowed
I don't see what's going wrong here. I can't interpret the compiler error here and I don't understand why the lifetimes aren't OK here.
The parse function on line 109 has this signature:
fn parse(&self, input: &'a [I]) -> Result<O>
pub type Result<O> = ::std::result::Result<O, Error>;
no problems writing the parsers and feeding in string literal as test data.
This works because all string literals have the 'static lifetime. When you switch to read from a file instead, the latent 'static is gone. The behavior of the code actually changes so that it triggers the error.
The question is then why your parser implementation expects a 'static input in the first place. I suspect that the example given in the pom read-me file is to be blamed here. For example it has the following code:
use pom::Parser;
fn space() -> Parser<u8, ()> {
one_of(b" \t\r\n").repeat(0..).discard()
}
pom::Parser<u8, ()> is actually an alias for pom::parser::Parser<'static, u8, ()>. If it were to be written as:
use pom::parser::Parser;
fn space<'a>() -> Parser<'a, u8, ()> {
one_of(b" \t\r\n").repeat(0..).discard()
}
then it should be able to handle both 'static and non-'static input. Make similar changes to your parser code and it will work again.