error

compiler error in a macro? o_O

* 1) bin: rustc  ../src/main.rs -L ../lib/ -o fs                                                                                           
<std macros>:6:9: 6:32 error: instantiating a type parameter with an incompatible type `&str`, which does not fulfill `Send`
<std macros>:6         ::std::rt::begin_unwind($msg, file!(), line!())
                       ^~~~~~~~~~~~~~~~~~~~~~~
<std macros>:1:1: 26:2 note: in expansion of fail!
../src/types.rs:41:4: 42:4 note: expansion site
error: aborting due to previous error

types.rs

use std::path::Path;
use std::fmt::{Show, Formatter, Result};
use std::io::FileStat;
use std::vec::Vec;



///represents a collection of paths used for batch processing
pub struct PathCollection {
	paths: Vec<Path>,
	///can be used by Operations to setup till where they have processed. useful to store information
	num_processed: uint,
}

impl PathCollection {
	pub fn new(paths: Vec<Path>) -> PathCollection {
		return PathCollection { paths: paths, num_processed: 0 }
	}

	///returns num_processed / len(Paths). can be used to get a measure of progress
	pub fn get_progress(&self) -> f32 {
		self.num_processed as f32 / self.paths.len() as f32  
	}

	pub fn get_current<'a>(&'a self) -> &'a Path {
		return self.paths.get(self.num_processed)
	}

	pub fn goto_next(&mut self) -> () {
		self.num_processed += 1;
		assert!(self.num_processed <= self.paths.len(), "asked to goto next where none exists")
	}
}

pub trait Operation {
	fn run(&mut self) -> bool;
	fn done(&self) -> bool;

	fn assert_done(&self, error: &str) {
		if !self.done() {
			fail!(error)
		}
	}
}

pub trait Progress {
	fn get_progress(&self) -> f32;
}

* 1) bin: rustc ../src/main.rs -L ../lib/ -o fs
<std macros>:6:9: 6:32 error: instantiating a type parameter with an incompatible type `&str`, which does not fulfill `Send`
<std macros>:6 ::std::rt::begin_unwind($msg, file!(), line!())
^~~~~~~~~~~~~~~~~~~~~~~
<std macros>:1:1: 26:2 note: in expansion of fail!
../src/types.rs:41:4: 42:4 note: expansion site
error: aborting due to previous error