Custom hooks with RPIT no longer compile in Rust 2024

[kawadakk]

Problem
#[hook] generates code that no longer compiles under Lifetime Capture Rules 2024 (RFC 3498).

Steps To Reproduce

# Cargo.toml
[package]
name = "foo"
edition = "2024"

[dependencies]
yew = { version = "0.21.0", features = ["csr"] }

// src/lib.rs
use yew::prelude::*;

#[hook]
pub fn use_foo() -> impl Sized {
    42
}

$ cargo +nightly-2024-12-12 check
error: lifetime may not live long enough
 --> src/lib.rs:3:1
  |
3 | #[hook]
  | -^^^^^-
  | |     |
  | |     return type of closure `impl Sized` contains a lifetime `'2`
  | let's call the lifetime of this reference `'1`
  | returning this value requires that `'1` must outlive `'2`
  |
  = note: this error originates in the attribute macro `hook` (in Nightly builds, run with -Z macro-backtrace for more info)

Expected behavior
Successful compilation as in Rust 2021

Screenshots
If applicable, add screenshots to help explain your problem.

Environment:

• Yew version: 0.21.0
• Rust version: nightly-2024-12-12
• Target, if relevant: N/A
• Build tool, if relevant: N/A
• OS, if relevant: N/A
• Browser and version, if relevant: N/A

Questionnaire

• I'm interested in fixing this myself but don't know where to start
• I would like to fix and I have a solution
• I don't have time to fix this right now, but maybe later

[kawadakk]

A possible work-around is to manually list all type and lifetime parameters in scope by + use<...>. Example:

#[hook]
// pub fn use_foo() -> impl Sized {
pub fn use_foo() -> impl Sized + use<> {
    42
}

#[hook]
// pub fn use_bar(x: &impl Clone) -> impl Clone {
pub fn use_bar<'a, X: Clone>(x: &'a X) -> impl Clone + use<'a, X> {
    42
}