Change:
Here is the error Here is the code that generates the error My system is x86_64 archlinux. The rust compiler version is Let me know if you guys need anything else. (The code is really short so it shouldn't be hard to just type it in to duplicate the bug)
It only needs one line for me
Workaround (in the sense that the compiler no longer ICE's): I think there is some unfortunate interaction here with the way we attempt to infer which kind of numeric literals are in the array (, , etc) and other code not being prepared to handle the that results when you don't have that information available.
This is almost certainly a duplicate of (but maybe the integer inference codepath is slightly different?).
This also causes the same ICE -
Similarly:
Looks like it's been fixed.

Discussion:
<ins> // Copyright 2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. use std::io; use std::vec; pub struct Container<'a> { reader: &'a mut Reader //~ ERROR explicit lifetime bound required } impl<'a> Container<'a> { pub fn wrap<'s>(reader: &'s mut Reader) -> Container<'s> { Container { reader: reader } } pub fn read_to(&mut self, vec: &mut [u8]) { self.reader.read(vec); } } pub fn for_stdin<'a>() -> Container<'a> { let mut r = io::stdin(); Container::wrap(&mut r as &mut Reader) } fn main() { let mut c = for_stdin(); let mut v = vec::Vec::from_elem(10, 0u8); c.read_to(v.as_mut_slice()); } </ins>

<ins> // Copyright 2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. fn blah() -> int { //~ ERROR not all control paths return a value 1i ; //~ NOTE consider removing this semicolon: } fn main() { } </ins>

<ins> // Copyright 2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. #![feature(struct_variant)] mod a { pub enum Enum { EnumStructVariant { x: u8, y: u8, z: u8 } } pub fn get_enum_struct_variant() -> () { EnumStructVariant { x: 1, y: 2, z: 3 } //~^ ERROR mismatched types: expected `()`, found `a::Enum` (expected (), found enum a::Enum) } } mod b { mod test { use a; fn test_enum_struct_variant() { let enum_struct_variant = ::a::get_enum_struct_variant(); match enum_struct_variant { a::EnumStructVariant { x, y, z } => { //~^ ERROR error: mismatched types: expected `()`, found a structure pattern } } } } } fn main() {} </ins>

<ins> // Copyright 2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. fn main() { let mut array = [1, 2, 3]; //~^ ERROR cannot determine a type for this local variable: cannot determine the type of this integ let pie_slice = array.slice(1, 2); } </ins>

<ins> // Copyright 2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. pub fn foo(params: Option<&[&str]>) -> uint { params.unwrap().head().unwrap().len() } fn main() { let name = "Foo"; let msg = foo(Some(&[name.as_slice()])); //~^ ERROR mismatched types: expected `core::option::Option<&[&str]>` assert_eq!(msg, 3); } </ins>

<ins> // Copyright 2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. fn main() { let v = &[]; //~ ERROR cannot determine a type for this local variable: unconstrained type let it = v.iter(); } </ins>

<ins> // Copyright 2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. // error-pattern:explicit failure pub fn main() { fail!(); println!("{}", 1i); } </ins>

<ins> // Copyright 2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. // error-pattern:bad input fn main() { Some("foo").unwrap_or(fail!("bad input")).to_string(); } </ins>

<ins> // Copyright 2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. pub mod two_tuple { trait T {} struct P<'a>(&'a T + 'a, &'a T + 'a); pub fn f<'a>(car: &'a T, cdr: &'a T) -> P<'a> { P(car, cdr) } } pub mod two_fields { trait T {} struct P<'a> { car: &'a T + 'a, cdr: &'a T + 'a } pub fn f<'a>(car: &'a T, cdr: &'a T) -> P<'a> { P{ car: car, cdr: cdr } } } fn main() {} </ins>

<ins> // Copyright 2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. fn main() { if true { proc(_) {} } else { proc(_: &mut ()) {} }; } </ins>