Closed as not planned
Description
I tried this code:
type Result<T> = std::result::Result<T, std::io::Error>;
pub(crate) struct Foo<'a> {
pub(crate) kernels: Vec<&'a str>,
}
impl<'a> Foo<'a> {
fn parse(buf: &'a [u8]) -> Result<Foo> {
let p = &mut StreamParser::new(buf);
let (m, p) = p.read_map()?;
m.try_foreach(p, |b| {
let b0 = Self::broke(b)?;
Ok(b0)
})?;
Ok(Foo {
kernels: Vec::new(),
})
}
fn broke<'b: 'a>(p: &'b mut StreamParser<'a>) -> Result<&'b mut StreamParser<'a>> {
Ok(p)
}
}
#[derive(Copy, Clone)]
pub(crate) struct StreamParser<'a> {
bytes: &'a [u8],
current_position: usize,
}
#[derive(Copy, Clone, Debug)]
pub(crate) struct Seq {
num_entries: usize,
}
impl Seq {
pub(crate) fn try_foreach<'a, 'b, F>(
&self,
p: &'b mut StreamParser<'a>,
mut f: F
) -> Result<&'b mut StreamParser<'a>>
where F: FnMut(&'b mut StreamParser<'a>) -> Result<&'b mut StreamParser<'a>>
{
(0..self.num_entries).try_fold(p, |p, _| (f)(p))
}
}
impl<'a> StreamParser<'a> {
pub(crate) fn new(bytes: &'a [u8]) -> StreamParser<'a> {
StreamParser {
bytes,
current_position: 0,
}
}
pub(crate) fn read_map(&mut self) -> Result<(Seq, &mut Self)> {
let c = self.read_u8()?;
Ok((
Seq {
num_entries: c as usize,
},
self,
))
}
fn read_u8(&mut self) -> Result<u8> {
let r = self.bytes[self.current_position];
self.current_position += 1;
Ok(r)
}
}The rustc in 1.63 compiles the code successfully while rustc 1.65.0-nightly (cf9ed0d 2022-09-15) fails to compile it:
7 | impl<'a> Foo<'a> {
| -- lifetime `'a` defined here
8 | fn parse(buf: &'a [u8]) -> Result<Foo> {
9 | let p = &mut StreamParser::new(buf);
| ^^^^^^^^^^^^^^^^^^^^^^ creates a temporary which is freed while still in use
10 | let (m, p) = p.read_map()?;
| ------------ argument requires that borrow lasts for `'a`
...
18 | }
Are there any changes in the language specifications that have tighten the lifetime rules?