Remove by-mutable-ref mode from the compiler

and test cases. Closes #3513

26 files changed, 59 insertions, 95 deletions

diff --git a/doc/rust.md b/doc/rust.md
index 31c52300312..66552c29017 100644
--- a/doc/rust.md
+++ b/doc/rust.md
@@ -2784,14 +2784,12 @@ aside a copy of that value to refer to. If this is not semantically safe (for
 example, if the referred-to value contains mutable fields), it will reject the
 program. If the compiler deems copying the value expensive, it will warn.
 
-A function can be declared to take an argument by mutable reference. This
-allows the function to write to the slot that the reference refers to.
-
-An example function that accepts an value by mutable reference:
+A function with an argument of type `&mut T`, for some type `T`, can write to
+the slot that its argument refers to. An example of such a function is:
 
 ~~~~~~~~
-fn incr(&i: int) {
-    i = i + 1;
+fn incr(i: &mut int) {
+    *i = *i + 1;
 }
 ~~~~~~~~
 
diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index e17b52fb27d..a50189cf598 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -574,7 +574,7 @@ impl<T:cmp::Eq> inferable<T> : cmp::Eq {
 
 // "resolved" mode: the real modes.
 #[auto_serialize]
-enum rmode { by_ref, by_val, by_mutbl_ref, by_move, by_copy }
+enum rmode { by_ref, by_val, by_move, by_copy }
 
 impl rmode : to_bytes::IterBytes {
     pure fn iter_bytes(+lsb0: bool, f: to_bytes::Cb) {
diff --git a/src/libsyntax/parse/obsolete.rs b/src/libsyntax/parse/obsolete.rs
index 782535f5c2b..828d498ca3c 100644
--- a/src/libsyntax/parse/obsolete.rs
+++ b/src/libsyntax/parse/obsolete.rs
@@ -22,7 +22,8 @@ pub enum ObsoleteSyntax {
     ObsoleteClassMethod,
     ObsoleteClassTraits,
     ObsoletePrivSection,
-    ObsoleteModeInFnType
+    ObsoleteModeInFnType,
+    ObsoleteByMutRefMode
 }
 
 impl ObsoleteSyntax : cmp::Eq {
@@ -94,6 +95,10 @@ impl parser : ObsoleteReporter {
                 "to use a (deprecated) mode in a fn type, you should \
                  give the argument an explicit name (like `&&v: int`)"
             ),
+            ObsoleteByMutRefMode => (
+                "by-mutable-reference mode",
+                "Declare an argument of type &mut T instead"
+            ),
         };
 
         self.report(sp, kind, kind_str, desc);
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 6bee9190a83..22c25186c91 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -20,13 +20,13 @@ use obsolete::{
     ObsoleteLowerCaseKindBounds, ObsoleteLet,
     ObsoleteFieldTerminator, ObsoleteStructCtor,
     ObsoleteWith, ObsoleteClassMethod, ObsoleteClassTraits,
-    ObsoleteModeInFnType
+    ObsoleteModeInFnType, ObsoleteByMutRefMode
 };
 use ast::{_mod, add, alt_check, alt_exhaustive, arg, arm, attribute,
              bind_by_ref, bind_by_implicit_ref, bind_by_value, bind_by_move,
              bitand, bitor, bitxor, blk, blk_check_mode, bound_const,
              bound_copy, bound_send, bound_trait, bound_owned, box, by_copy,
-             by_move, by_mutbl_ref, by_ref, by_val, capture_clause,
+             by_move, by_ref, by_val, capture_clause,
              capture_item, cdir_dir_mod, cdir_src_mod, cdir_view_item,
              class_immutable, class_mutable,
              crate, crate_cfg, crate_directive, decl, decl_item, decl_local,
@@ -570,9 +570,10 @@ impl parser {
 
     fn parse_arg_mode() -> mode {
         if self.eat(token::BINOP(token::AND)) {
-            self.span_fatal(copy self.last_span,
-                            ~"Obsolete syntax has no effect");
-            expl(by_mutbl_ref)
+            self.obsolete(copy self.span,
+                          ObsoleteByMutRefMode);
+            // Bogus mode, but doesn't matter since it's an error
+            expl(by_ref)
         } else if self.eat(token::BINOP(token::MINUS)) {
             expl(by_move)
         } else if self.eat(token::ANDAND) {
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index d08b20eed84..bff356e5cb7 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -1688,7 +1688,6 @@ fn print_fn_block_args(s: ps, decl: ast::fn_decl,
 
 fn mode_to_str(m: ast::mode) -> ~str {
     match m {
-      ast::expl(ast::by_mutbl_ref) => ~"&",
       ast::expl(ast::by_move) => ~"-",
       ast::expl(ast::by_ref) => ~"&&",
       ast::expl(ast::by_val) => ~"++",
diff --git a/src/rustc/metadata/tydecode.rs b/src/rustc/metadata/tydecode.rs
index f3fa0e3f350..1375ff2d0be 100644
--- a/src/rustc/metadata/tydecode.rs
+++ b/src/rustc/metadata/tydecode.rs
@@ -394,7 +394,6 @@ fn parse_arg(st: @pstate, conv: conv_did) -> ty::arg {
 
 fn parse_mode(st: @pstate) -> ast::mode {
     let m = ast::expl(match next(st) {
-        '&' => ast::by_mutbl_ref,
         '-' => ast::by_move,
         '+' => ast::by_copy,
         '=' => ast::by_ref,
diff --git a/src/rustc/metadata/tyencode.rs b/src/rustc/metadata/tyencode.rs
index 611ffb598ae..69689b16e15 100644
--- a/src/rustc/metadata/tyencode.rs
+++ b/src/rustc/metadata/tyencode.rs
@@ -333,7 +333,6 @@ fn enc_arg(w: io::Writer, cx: @ctxt, arg: ty::arg) {
 
 fn enc_mode(w: io::Writer, cx: @ctxt, m: mode) {
     match ty::resolved_mode(cx.tcx, m) {
-      by_mutbl_ref => w.write_char('&'),
       by_move => w.write_char('-'),
       by_copy => w.write_char('+'),
       by_ref => w.write_char('='),
diff --git a/src/rustc/middle/borrowck/check_loans.rs b/src/rustc/middle/borrowck/check_loans.rs
index 5ff2a8933a9..cc8d89a8ace 100644
--- a/src/rustc/middle/borrowck/check_loans.rs
+++ b/src/rustc/middle/borrowck/check_loans.rs
@@ -529,7 +529,7 @@ impl check_loan_ctxt {
                 ast::by_move => {
                     self.check_move_out(*arg);
                 }
-                ast::by_mutbl_ref | ast::by_ref |
+                ast::by_ref |
                 ast::by_copy | ast::by_val => {
                 }
             }
diff --git a/src/rustc/middle/borrowck/gather_loans.rs b/src/rustc/middle/borrowck/gather_loans.rs
index 327db51518b..5dfde8c9af6 100644
--- a/src/rustc/middle/borrowck/gather_loans.rs
+++ b/src/rustc/middle/borrowck/gather_loans.rs
@@ -115,10 +115,6 @@ fn req_loans_in_expr(ex: @ast::expr,
         let scope_r = ty::re_scope(ex.id);
         for vec::each2(args, arg_tys) |arg, arg_ty| {
             match ty::resolved_mode(self.tcx(), arg_ty.mode) {
-              ast::by_mutbl_ref => {
-                let arg_cmt = self.bccx.cat_expr(*arg);
-                self.guarantee_valid(arg_cmt, m_mutbl, scope_r);
-              }
               ast::by_ref => {
                 let arg_cmt = self.bccx.cat_expr(*arg);
                 self.guarantee_valid(arg_cmt, m_imm,  scope_r);
diff --git a/src/rustc/middle/kind.rs b/src/rustc/middle/kind.rs
index 9aff382775c..e2b85441a8f 100644
--- a/src/rustc/middle/kind.rs
+++ b/src/rustc/middle/kind.rs
@@ -323,7 +323,7 @@ fn check_expr(e: @expr, cx: ctx, v: visit::vt<ctx>) {
         for ty::ty_fn_args(ty::expr_ty(cx.tcx, f)).each |arg_t| {
             match ty::arg_mode(cx.tcx, *arg_t) {
               by_copy => maybe_copy(cx, args[i], None),
-              by_ref | by_val | by_mutbl_ref | by_move => ()
+              by_ref | by_val | by_move => ()
             }
             i += 1u;
         }
@@ -335,7 +335,7 @@ fn check_expr(e: @expr, cx: ctx, v: visit::vt<ctx>) {
             Some(ref mme) => {
                 match ty::arg_mode(cx.tcx, mme.self_arg) {
                     by_copy => maybe_copy(cx, lhs, None),
-                    by_ref | by_val | by_mutbl_ref | by_move => ()
+                    by_ref | by_val | by_move => ()
                 }
             }
             _ => ()
@@ -465,14 +465,7 @@ fn check_imm_free_var(cx: ctx, def: def, sp: span) {
             cx.tcx.sess.span_err(sp, msg);
         }
       }
-      def_arg(_, mode) => {
-        match ty::resolved_mode(cx.tcx, mode) {
-          by_ref | by_val | by_move | by_copy => { /* ok */ }
-          by_mutbl_ref => {
-            cx.tcx.sess.span_err(sp, msg);
-          }
-        }
-      }
+      def_arg(*) => { /* ok */ }
       def_upvar(_, def1, _, _) => {
         check_imm_free_var(cx, *def1, sp);
       }
diff --git a/src/rustc/middle/liveness.rs b/src/rustc/middle/liveness.rs
index 6b39a21a7ba..12d63cdacbf 100644
--- a/src/rustc/middle/liveness.rs
+++ b/src/rustc/middle/liveness.rs
@@ -398,7 +398,7 @@ impl IrMaps {
 
             (*v).push(id);
           }
-          Arg(_, _, by_ref) | Arg(_, _, by_mutbl_ref) |
+          Arg(_, _, by_ref) |
           Arg(_, _, by_val) | Self | Field(_) | ImplicitRet |
           Local(LocalInfo {kind: FromMatch(bind_by_implicit_ref), _}) => {
             debug!("--but it is not owned");
@@ -919,7 +919,7 @@ impl Liveness {
         // inputs passed by & mode should be considered live on exit:
         for decl.inputs.each |arg| {
             match ty::resolved_mode(self.tcx, arg.mode) {
-              by_mutbl_ref | by_ref | by_val => {
+              by_ref | by_val => {
                 // These are "non-owned" modes, so register a read at
                 // the end.  This will prevent us from moving out of
                 // such variables but also prevent us from registering
@@ -1573,7 +1573,7 @@ fn check_expr(expr: @expr, &&self: @Liveness, vt: vt<@Liveness>) {
         let targs = ty::ty_fn_args(ty::expr_ty(self.tcx, f));
         for vec::each2(args, targs) |arg_expr, arg_ty| {
             match ty::resolved_mode(self.tcx, arg_ty.mode) {
-                by_val | by_copy | by_ref | by_mutbl_ref => {}
+                by_val | by_copy | by_ref => {}
                 by_move => {
                     self.check_move_from_expr(*arg_expr, vt);
                 }
@@ -1865,24 +1865,7 @@ impl @Liveness {
     fn warn_about_unused_args(sp: span, decl: fn_decl, entry_ln: LiveNode) {
         for decl.inputs.each |arg| {
             let var = self.variable(arg.id, arg.ty.span);
-            match ty::resolved_mode(self.tcx, arg.mode) {
-              by_mutbl_ref => {
-                // for mutable reference arguments, something like
-                //    x = 1;
-                // is not worth warning about, as it has visible
-                // side effects outside the fn.
-                match self.assigned_on_entry(entry_ln, var) {
-                  Some(_) => { /*ok*/ }
-                  None => {
-                    // but if it is not written, it ought to be used
-                    self.warn_about_unused(sp, entry_ln, var);
-                  }
-                }
-              }
-              by_val | by_ref | by_move | by_copy => {
-                self.warn_about_unused(sp, entry_ln, var);
-              }
-            }
+            self.warn_about_unused(sp, entry_ln, var);
         }
     }
 
diff --git a/src/rustc/middle/mem_categorization.rs b/src/rustc/middle/mem_categorization.rs
index fe465db1312..dc5874ea2cf 100644
--- a/src/rustc/middle/mem_categorization.rs
+++ b/src/rustc/middle/mem_categorization.rs
@@ -523,9 +523,6 @@ impl &mem_categorization_ctxt {
             // m: mutability of the argument
             // lp: loan path, must be none for aliasable things
             let {m,lp} = match ty::resolved_mode(self.tcx, mode) {
-              ast::by_mutbl_ref => {
-                {m: m_mutbl, lp: None}
-              }
               ast::by_move | ast::by_copy => {
                 {m: m_imm, lp: Some(@lp_arg(vid))}
               }
diff --git a/src/rustc/middle/trans/base.rs b/src/rustc/middle/trans/base.rs
index afa008fdbb7..95711f8da36 100644
--- a/src/rustc/middle/trans/base.rs
+++ b/src/rustc/middle/trans/base.rs
@@ -1503,7 +1503,7 @@ fn copy_args_to_allocas(fcx: fn_ctxt,
         // the event it's not truly needed.
         let llarg;
         match ty::resolved_mode(tcx, arg_ty.mode) {
-            ast::by_ref | ast::by_mutbl_ref => {
+            ast::by_ref => {
                 llarg = raw_llarg;
             }
             ast::by_move | ast::by_copy => {
diff --git a/src/rustc/middle/trans/callee.rs b/src/rustc/middle/trans/callee.rs
index e7b4dd171e3..c851c5bc725 100644
--- a/src/rustc/middle/trans/callee.rs
+++ b/src/rustc/middle/trans/callee.rs
@@ -592,7 +592,7 @@ fn trans_arg_expr(bcx: block,
             DoAutorefArg => { val = arg_datum.to_ref_llval(bcx); }
             DontAutorefArg => {
                 match arg_mode {
-                    ast::by_ref | ast::by_mutbl_ref => {
+                    ast::by_ref => {
                         val = arg_datum.to_ref_llval(bcx);
                     }
 
diff --git a/src/rustc/middle/trans/meth.rs b/src/rustc/middle/trans/meth.rs
index b4a64abeed7..d8a2fda4d14 100644
--- a/src/rustc/middle/trans/meth.rs
+++ b/src/rustc/middle/trans/meth.rs
@@ -154,7 +154,7 @@ fn trans_method_callee(bcx: block, callee_id: ast::node_id,
         typeck::method_trait(_, off, vstore) => {
             trans_trait_callee(bcx, callee_id, off, self, vstore)
         }
-        typeck::method_self(_, off) => {
+        typeck::method_self(*) => {
             bcx.tcx().sess.span_bug(self.span, ~"self method call");
         }
     }
diff --git a/src/rustc/middle/trans/reflect.rs b/src/rustc/middle/trans/reflect.rs
index 3996f0ff5ee..c105caecaeb 100644
--- a/src/rustc/middle/trans/reflect.rs
+++ b/src/rustc/middle/trans/reflect.rs
@@ -210,7 +210,6 @@ impl reflector {
                   ast::expl(e) => match e {
                     ast::by_ref => 1u,
                     ast::by_val => 2u,
-                    ast::by_mutbl_ref => 3u,
                     ast::by_move => 4u,
                     ast::by_copy => 5u
                   }
diff --git a/src/rustc/middle/trans/type_use.rs b/src/rustc/middle/trans/type_use.rs
index 8eabf26e217..ee247eb5db7 100644
--- a/src/rustc/middle/trans/type_use.rs
+++ b/src/rustc/middle/trans/type_use.rs
@@ -53,7 +53,7 @@ fn type_uses_for(ccx: @crate_ctxt, fn_id: def_id, n_tps: uint)
                     by_val | by_move | by_copy => {
                         type_needs(cx, use_repr, arg.ty);
                     }
-                    by_ref | by_mutbl_ref => {}
+                    by_ref => {}
                 }
             }
         }
diff --git a/src/test/bench/task-perf-word-count-generic.rs b/src/test/bench/task-perf-word-count-generic.rs
index 97b031c6024..30add8c730c 100644
--- a/src/test/bench/task-perf-word-count-generic.rs
+++ b/src/test/bench/task-perf-word-count-generic.rs
@@ -144,7 +144,7 @@ mod map_reduce {
     fn start_mappers<K1: Copy Send, K2: Hash IterBytes Eq Const Copy Send,
                      V: Copy Send>(
         map: &mapper<K1, K2, V>,
-        &ctrls: ~[ctrl_proto::server::open<K2, V>],
+        ctrls: &mut ~[ctrl_proto::server::open<K2, V>],
         inputs: &~[K1])
         -> ~[joinable_task]
     {
@@ -213,9 +213,9 @@ mod map_reduce {
         let mut is_done = false;
 
         fn get<V: Copy Send>(p: Port<reduce_proto<V>>,
-                             &ref_count: int, &is_done: bool)
+                             ref_count: &mut int, is_done: &mut bool)
            -> Option<V> {
-            while !is_done || ref_count > 0 {
+            while !*is_done || *ref_count > 0 {
                 match recv(p) {
                   emit_val(v) => {
                     // error!("received %d", v);
@@ -223,16 +223,16 @@ mod map_reduce {
                   }
                   done => {
                     // error!("all done");
-                    is_done = true;
+                    *is_done = true;
                   }
-                  addref => { ref_count += 1; }
-                  release => { ref_count -= 1; }
+                  addref => { *ref_count += 1; }
+                  release => { *ref_count -= 1; }
                 }
             }
             return None;
         }
 
-        (*reduce)(&key, || get(p, ref_count, is_done) );
+        (*reduce)(&key, || get(p, &mut ref_count, &mut is_done) );
     }
 
     fn map_reduce<K1: Copy Send, K2: Hash IterBytes Eq Const Copy Send, V: Copy Send>(
@@ -246,7 +246,7 @@ mod map_reduce {
         // to do the rest.
 
         let reducers = map::HashMap();
-        let mut tasks = start_mappers(&map, ctrl, &inputs);
+        let mut tasks = start_mappers(&map, &mut ctrl, &inputs);
         let mut num_mappers = vec::len(inputs) as int;
 
         while num_mappers > 0 {
diff --git a/src/test/compile-fail/deprecated-mode-fn-arg.rs b/src/test/compile-fail/deprecated-mode-fn-arg.rs
index 2c20e604f50..bb466e2c00b 100644
--- a/src/test/compile-fail/deprecated-mode-fn-arg.rs
+++ b/src/test/compile-fail/deprecated-mode-fn-arg.rs
@@ -1,11 +1,9 @@
 #[forbid(deprecated_mode)];
 
-fn foo(_f: fn(&i: int)) { //~ ERROR explicit mode
-    //~^ WARNING Obsolete syntax has no effect
+fn foo(_f: fn(&i: int)) { //~ ERROR by-mutable-reference mode
 }
 
-type Bar = fn(&i: int); //~ ERROR explicit mode
-    //~^ WARNING Obsolete syntax has no effect
+type Bar = fn(&i: int); //~ ERROR by-mutable-reference mode
 
 fn main() {
 }
\ No newline at end of file
diff --git a/src/test/compile-fail/unnamed_argument_mode.rs b/src/test/compile-fail/unnamed_argument_mode.rs
index 36e6edc96f9..77d40aae6a2 100644
--- a/src/test/compile-fail/unnamed_argument_mode.rs
+++ b/src/test/compile-fail/unnamed_argument_mode.rs
@@ -1,11 +1,8 @@
-//error-pattern: mismatched types
+//error-pattern: by-mutable-reference mode
 
 fn bad(&a: int) {
 }
 
-// unnamed argument &int is now parsed x: &int
-// it's not parsed &x: int anymore
-
 fn called(f: fn(&int)) {
 }
 
diff --git a/src/test/run-pass/argument-passing.rs b/src/test/run-pass/argument-passing.rs
index 2a839863455..e8aaf88374f 100644
--- a/src/test/run-pass/argument-passing.rs
+++ b/src/test/run-pass/argument-passing.rs
@@ -1,10 +1,10 @@
 // xfail-fast
 #[legacy_modes];
 
-fn f1(a: {mut x: int}, &b: int, -c: int) -> int {
-    let r = a.x + b + c;
+fn f1(a: {mut x: int}, b: &mut int, -c: int) -> int {
+    let r = a.x + *b + c;
     a.x = 0;
-    b = 10;
+    *b = 10;
     return r;
 }
 
@@ -12,7 +12,7 @@ fn f2(a: int, f: fn(int)) -> int { f(1); return a; }
 
 fn main() {
     let mut a = {mut x: 1}, b = 2, c = 3;
-    assert (f1(a, b, c) == 6);
+    assert (f1(a, &mut b, c) == 6);
     assert (a.x == 0);
     assert (b == 10);
     assert (f2(a.x, |x| a.x = 50 ) == 0);
diff --git a/src/test/run-pass/fn-bare-assign.rs b/src/test/run-pass/fn-bare-assign.rs
index ae6b1a1079f..71996552d0c 100644
--- a/src/test/run-pass/fn-bare-assign.rs
+++ b/src/test/run-pass/fn-bare-assign.rs
@@ -1,15 +1,15 @@
-fn f(i: int, &called: bool) {
+fn f(i: int, called: &mut bool) {
     assert i == 10;
-    called = true;
+    *called = true;
 }
 
-fn g(f: extern fn(int, &v: bool), &called: bool) {
+fn g(f: extern fn(int, v: &mut bool), called: &mut bool) {
     f(10, called);
 }
 
 fn main() {
     let mut called = false;
     let h = f;
-    g(h, called);
+    g(h, &mut called);
     assert called == true;
 }
\ No newline at end of file
diff --git a/src/test/run-pass/lazy-and-or.rs b/src/test/run-pass/lazy-and-or.rs
index 7ad71854dc4..3e84c9f6f72 100644
--- a/src/test/run-pass/lazy-and-or.rs
+++ b/src/test/run-pass/lazy-and-or.rs
@@ -1,12 +1,12 @@
 
 
-fn incr(&x: int) -> bool { x += 1; assert (false); return false; }
+fn incr(x: &mut int) -> bool { *x += 1; assert (false); return false; }
 
 fn main() {
     let x = 1 == 2 || 3 == 3;
     assert (x);
     let mut y: int = 10;
-    log(debug, x || incr(y));
+    log(debug, x || incr(&mut y));
     assert (y == 10);
     if true && x { assert (true); } else { assert (false); }
 }
diff --git a/src/test/run-pass/mutable-alias-vec.rs b/src/test/run-pass/mutable-alias-vec.rs
index e54197ccc6b..d5b1eef993e 100644
--- a/src/test/run-pass/mutable-alias-vec.rs
+++ b/src/test/run-pass/mutable-alias-vec.rs
@@ -3,13 +3,13 @@
 // -*- rust -*-
 extern mod std;
 
-fn grow(&v: ~[int]) { v += ~[1]; }
+fn grow(v: &mut ~[int]) { *v += ~[1]; }
 
 fn main() {
     let mut v: ~[int] = ~[];
-    grow(v);
-    grow(v);
-    grow(v);
+    grow(&mut v);
+    grow(&mut v);
+    grow(&mut v);
     let len = vec::len::<int>(v);
     log(debug, len);
     assert (len == 3 as uint);
diff --git a/src/test/run-pass/unique-fn-arg-mut.rs b/src/test/run-pass/unique-fn-arg-mut.rs
index 8d9386d70ff..36d1d689f5f 100644
--- a/src/test/run-pass/unique-fn-arg-mut.rs
+++ b/src/test/run-pass/unique-fn-arg-mut.rs
@@ -1,9 +1,9 @@
-fn f(&i: ~int) {
-    i = ~200;
+fn f(i: &mut ~int) {
+    *i = ~200;
 }
 
 fn main() {
     let mut i = ~100;
-    f(i);
+    f(&mut i);
     assert *i == 200;
 }
\ No newline at end of file
diff --git a/src/test/run-pass/writealias.rs b/src/test/run-pass/writealias.rs
index 9dba2e2adfd..eb3fa602f12 100644
--- a/src/test/run-pass/writealias.rs
+++ b/src/test/run-pass/writealias.rs
@@ -4,10 +4,10 @@
 // -*- rust -*-
 type point = {x: int, y: int, mut z: int};
 
-fn f(&p: point) { p.z = 13; }
+fn f(p: &mut point) { p.z = 13; }
 
 fn main() {
     let mut x: point = {x: 10, y: 11, mut z: 12};
-    f(x);
+    f(&mut x);
     assert (x.z == 13);
 }