gistfile1.rs

rustc 0.10-pre (0a5138c 2014-03-04 13:16:41 -0800)

/// A struct with borrowed pointer to a closure.
/// This is to be able to reuse the closure then struct runs out of scope.

pub struct Test<'a> {
	f: &'a 'a ||
}

impl<'a> Test<'a> {
	pub fn new(f: &'a ||) -> Test<'a> {
		Test { f: f }
	}
}

pub struct Test2<'a> {
	f: Option<&'a 'a ||>
}

impl<'a> Test2<'a> {
	pub fn new(f: &'a ||) -> Test2<'a> {
		Test2 { f: Some(f) }
	}
}

fn main() {
	let x = || println!("hello!");
	
    // Works
	(*Test::new(&x).f)();

    // Fails
	(*Test2::new(&x).f.unwrap())();
}


Compiler error:
optionclosure.rs:21:3: 21:23 error: cannot infer an appropriate lifetime for region in type/impl due to conflicting requirements
optionclosure.rs:21 		Test2 { f: Some(f) }
                    		^~~~~~~~~~~~~~~~~~~~
optionclosure.rs:21:14: 21:21 note: first, the lifetime cannot outlive the call at 21:13...
optionclosure.rs:21 		Test2 { f: Some(f) }
                    		           ^~~~~~~
optionclosure.rs:21:14: 21:21 note: ...so that return value is valid for the call
optionclosure.rs:21 		Test2 { f: Some(f) }
                    		           ^~~~~~~
optionclosure.rs:20:37: 22:3 note: but, the lifetime must be valid for the lifetime &'a  as defined on the block at 20:36...
optionclosure.rs:20 	pub fn new(f: &'a ||) -> Test2<'a> {
optionclosure.rs:21 		Test2 { f: Some(f) }
optionclosure.rs:22 	}
optionclosure.rs:21:3: 21:23 note: ...so that types are compatible (expected `Test2<'a>` but found `Test2<>`)
optionclosure.rs:21 		Test2 { f: Some(f) }