auto merge of #6784 : nikomatsakis/rust/moves-into-borrowck, r=pcwalton

Move the computation of what data is moved out of `liveness` and into `borrowck`. The resulting code is cleaner, since before we had a split distribution of responsibilities, and also this avoids having multiple implementations of the dataflow code. Liveness is still used to report warnings about useless writes. This will go away when we get the control-flow graph code landed (working on that).

Also adds borrow checker documentation.

Fixes #4384.
Required to support once fns and to properly fix closures (#2202).
First step to generalize our treatment of moves somewhat as well.

src/librust/rust.rc

@@ -152,15 +152,15 @@ fn cmd_help(args: &[~str]) -> ValidUsage {
     }
 
     match args {
-        [command_string] => print_usage(command_string),
-        _                => Invalid
+        [ref command_string] => print_usage(copy *command_string),
+        _                    => Invalid
     }
 }
 
 fn cmd_test(args: &[~str]) -> ValidUsage {
     match args {
-        [filename] => {
-            let test_exec = Path(filename).filestem().unwrap() + "test~";
+        [ref filename] => {
+            let test_exec = Path(*filename).filestem().unwrap() + "test~";
             invoke("rustc", &[~"--test", filename.to_owned(),
                               ~"-o", test_exec.to_owned()], rustc::main);
             let exit_code = run::process_status(~"./" + test_exec, []);
@@ -172,8 +172,8 @@ fn cmd_test(args: &[~str]) -> ValidUsage {
 
 fn cmd_run(args: &[~str]) -> ValidUsage {
     match args {
-        [filename, ..prog_args] => {
-            let exec = Path(filename).filestem().unwrap() + "~";
+        [ref filename, ..prog_args] => {
+            let exec = Path(*filename).filestem().unwrap() + "~";
             invoke("rustc", &[filename.to_owned(), ~"-o", exec.to_owned()],
                    rustc::main);
             let exit_code = run::process_status(~"./"+exec, prog_args);

src/librustc/driver/driver.rs

@@ -263,8 +263,8 @@ pub fn compile_rest(sess: Session,
         time(time_passes, ~"loop checking", ||
              middle::check_loop::check_crate(ty_cx, crate));
 
-        let middle::moves::MoveMaps {moves_map, variable_moves_map,
-                                     moved_variables_set, capture_map} =
+        let middle::moves::MoveMaps {moves_map, moved_variables_set,
+                                     capture_map} =
             time(time_passes, ~"compute moves", ||
                  middle::moves::compute_moves(ty_cx, method_map, crate));
 
@@ -274,7 +274,6 @@ pub fn compile_rest(sess: Session,
 
         time(time_passes, ~"liveness checking", ||
              middle::liveness::check_crate(ty_cx, method_map,
-                                           variable_moves_map,
                                            capture_map, crate));
 
         let (root_map, write_guard_map) =