auto merge of #10042 : thestinger/rust/fail, r=sanxiyn

Closes #10023

Author: bors

src/libstd/rt/borrowck.rs

@@ -57,7 +57,7 @@ pub fn clear_task_borrow_list() {
     let _ = try_take_task_borrow_list();
 }
 
-unsafe fn fail_borrowed(box: *mut raw::Box<()>, file: *c_char, line: size_t) {
+unsafe fn fail_borrowed(box: *mut raw::Box<()>, file: *c_char, line: size_t) -> ! {
     debug_borrow("fail_borrowed: ", box, 0, 0, file, line);
 
     match try_take_task_borrow_list() {

src/libstd/unstable/lang.rs

@@ -22,8 +22,7 @@ pub fn fail_(expr: *c_char, file: *c_char, line: size_t) -> ! {
 }
 
 #[lang="fail_bounds_check"]
-pub fn fail_bounds_check(file: *c_char, line: size_t,
-                         index: size_t, len: size_t) {
+pub fn fail_bounds_check(file: *c_char, line: size_t, index: size_t, len: size_t) -> ! {
     let msg = format!("index out of bounds: the len is {} but the index is {}",
                       len as uint, index as uint);
     do msg.with_c_str |buf| {