How do I use Iterator's #map with #fold in rust?

rustc 0.13.0-nightly (f168c12c5 2014-10-25 20:57:10 +0000)

I have the following code.

fn main() { let nums = vec![1i,2,3]; let strings = nums.iter() .map(|n| n.to_string()) .fold(String::new, |a, b| a.push_str(b.as_slice())); assert_eq!("123", strings.as_slice()); } 

It should convert the integers in nums to their string representations and join them to one big String.

Here's what I get from rustc:

test2.rs:6:31: 6:53 error: type `fn() -> collections::string::String` does not implement any method in scope named `push_str` test2.rs:6 .fold(String::new, |a, b| a.push_str(b.as_slice())); ^~~~~~~~~~~~~~~~~~~~~~ test2.rs:8:29: 8:39 error: type `fn() -> collections::string::String` does not implement any method in scope named `as_slice` test2.rs:8 assert_eq!("123", strings.as_slice()); ^~~~~~~~~~ <std macros>:6:23: 6:33 error: the type of this value must be known in this context <std macros>:6 if !((*given_val == *expected_val) && ^~~~~~~~~~ <std macros>:1:1: 14:2 note: in expansion of assert_eq! test2.rs:8:3: 8:41 note: expansion site <std macros>:6:23: 6:33 error: the type of this value must be known in this context <std macros>:6 if !((*given_val == *expected_val) && ^~~~~~~~~~ <std macros>:1:1: 14:2 note: in expansion of assert_eq! test2.rs:8:3: 8:41 note: expansion site <std macros>:6:37: 6:50 error: the type of this value must be known in this context <std macros>:6 if !((*given_val == *expected_val) && ^~~~~~~~~~~~~ <std macros>:1:1: 14:2 note: in expansion of assert_eq! test2.rs:8:3: 8:41 note: expansion site <std macros>:7:23: 7:36 error: the type of this value must be known in this context <std macros>:7 (*expected_val == *given_val)) { ^~~~~~~~~~~~~ <std macros>:1:1: 14:2 note: in expansion of assert_eq! test2.rs:8:3: 8:41 note: expansion site error: aborting due to 6 previous errors 

So it complains about the type fn() -> collections::string::String, but I was expecting the result of the map to be just a plain collections::string::String.

Did I do anything wrong here, or is map not supposed to be used like I tried it in the example?

EDIT:

haha ok I found the mistake, String::new is a fn() -> collections::string::String, so it was a typo!

correct is .fold(String::new(), |a, b| a.push_string(b.as_slice()));