librustc: Implement moves based on type. r=nmatsakis

src/libcore/option.rs

@@ -150,8 +150,8 @@ pub pure fn or<T>(opta: Option<T>, optb: Option<T>) -> Option<T> {
     /*!
      * Returns the leftmost some() value, or none if both are none.
      */
-    match opta {
-        Some(_) => move opta,
+    match move opta {
+        Some(move opta) => Some(move opta),
         _ => move optb
     }
 }

src/libcore/pipes.rs

@@ -1029,9 +1029,9 @@ impl<T: Send> Port<T>: Recv<T> {
     pure fn peek() -> bool unsafe {
         let mut endp = None;
         endp <-> self.endp;
-        let peek = match endp {
-          Some(ref endp) => pipes::peek(endp),
-          None => fail ~"peeking empty stream"
+        let peek = match &endp {
+          &Some(ref endp) => pipes::peek(endp),
+          &None => fail ~"peeking empty stream"
         };
         self.endp <-> endp;
         peek

src/librustc/driver/driver.rs

@@ -251,6 +251,9 @@ fn compile_upto(sess: Session, cfg: ast::crate_cfg,
         time(time_passes, ~"alt checking", ||
              middle::check_alt::check_crate(ty_cx, crate));
 
+        time(time_passes, ~"mode computation", ||
+             middle::mode::compute_modes(ty_cx, method_map, crate));
+
         let last_use_map =
             time(time_passes, ~"liveness checking", ||
                  middle::liveness::check_crate(ty_cx, method_map, crate));

src/librustc/metadata/common.rs

@@ -131,7 +131,8 @@ enum astencode_tag { // Reserves 0x50 -- 0x6f
     tag_table_method_map = 0x60,
     tag_table_vtable_map = 0x61,
     tag_table_adjustments = 0x62,
-    tag_table_legacy_boxed_trait = 0x63
+    tag_table_legacy_boxed_trait = 0x63,
+    tag_table_value_mode = 0x64
 }
 
 const tag_item_trait_method_sort: uint = 0x70;

src/librustc/middle/astencode.rs

@@ -856,6 +856,15 @@ fn encode_side_tables_for_id(ecx: @e::encode_ctxt,
             ebml_w.id(id);
         }
     }
+
+    do option::iter(&tcx.value_modes.find(id)) |vm| {
+        do ebml_w.tag(c::tag_table_value_mode) {
+            ebml_w.id(id);
+            do ebml_w.tag(c::tag_table_val) {
+                (*vm).serialize(&ebml_w)
+            }
+        }
+    }
 }
 
 trait doc_decoder_helpers {
@@ -990,6 +999,9 @@ fn decode_side_tables(xcx: extended_decode_ctxt,
                 let adj: @ty::AutoAdjustment = @deserialize(val_dsr);
                 adj.tr(xcx);
                 dcx.tcx.adjustments.insert(id, adj);
+            } else if tag == (c::tag_table_value_mode as uint) {
+                let vm: ty::ValueMode = deserialize(val_dsr);
+                dcx.tcx.value_modes.insert(id, vm);
             } else {
                 xcx.dcx.tcx.sess.bug(
                     fmt!("unknown tag found in side tables: %x", tag));

src/librustc/middle/kind.rs

@@ -12,6 +12,7 @@ use syntax::{visit, ast_util};
 use syntax::ast::*;
 use syntax::codemap::span;
 use middle::ty::{Kind, kind_copyable, kind_noncopyable, kind_const};
+use middle::ty::{CopyValue, MoveValue, ReadValue};
 use std::map::HashMap;
 use util::ppaux::{ty_to_str, tys_to_str};
 use syntax::print::pprust::expr_to_str;
@@ -480,8 +481,16 @@ fn check_copy_ex(cx: ctx, ex: @expr, implicit_copy: bool,
         // borrowed unique value isn't really a copy
         !is_autorefd(cx, ex)
     {
-        let ty = ty::expr_ty(cx.tcx, ex);
-        check_copy(cx, ex.id, ty, ex.span, implicit_copy, why);
+        match cx.tcx.value_modes.find(ex.id) {
+            None => cx.tcx.sess.span_bug(ex.span, ~"no value mode for lval"),
+            Some(MoveValue) | Some(ReadValue) => {} // Won't be a copy.
+            Some(CopyValue) => {
+                debug!("(kind checking) is a copy value: `%s`",
+                       expr_to_str(ex, cx.tcx.sess.intr()));
+                let ty = ty::expr_ty(cx.tcx, ex);
+                check_copy(cx, ex.id, ty, ex.span, implicit_copy, why);
+            }
+        }
     }
 
     fn is_autorefd(cx: ctx, ex: @expr) -> bool {

src/librustc/middle/liveness.rs

@@ -111,6 +111,7 @@ use syntax::codemap::span;
 use syntax::ast::*;
 use io::WriterUtil;
 use capture::{cap_move, cap_drop, cap_copy, cap_ref};
+use middle::ty::MoveValue;
 
 export check_crate;
 export last_use_map;
@@ -1533,6 +1534,22 @@ fn check_expr(expr: @expr, &&self: @Liveness, vt: vt<@Liveness>) {
         for self.variable_from_def_map(expr.id, expr.span).each |var| {
             let ln = self.live_node(expr.id, expr.span);
             self.consider_last_use(expr, ln, *var);
+
+            match self.tcx.value_modes.find(expr.id) {
+                Some(MoveValue) => {
+                    debug!("(checking expr) is a move: `%s`",
+                           expr_to_str(expr, self.tcx.sess.intr()));
+                    self.check_move_from_var(expr.span, ln, *var);
+                }
+                Some(v) => {
+                    debug!("(checking expr) not a move (%?): `%s`",
+                           v,
+                           expr_to_str(expr, self.tcx.sess.intr()));
+                }
+                None => {
+                    fail ~"no mode for lval";
+                }
+            }
         }
 
         visit::visit_expr(expr, self, vt);

src/librustc/middle/mode.rs

@@ -0,0 +1,181 @@
+use middle::ty;
+use middle::ty::{CopyValue, MoveValue, ReadValue, ValueMode, ctxt};
+use middle::typeck::{method_map, method_map_entry};
+
+use core::vec;
+use std::map::HashMap;
+use syntax::ast::{by_copy, by_move, by_ref, by_val, crate, expr, expr_assign};
+use syntax::ast::{expr_addr_of, expr_assign_op, expr_binary, expr_call};
+use syntax::ast::{expr_copy, expr_field, expr_index, expr_method_call};
+use syntax::ast::{expr_path, expr_swap, expr_unary, node_id, sty_uniq};
+use syntax::ast::{sty_value};
+use syntax::ast::{box, uniq, deref, not, neg, expr_paren};
+use syntax::visit;
+use syntax::visit::vt;
+
+struct VisitContext {
+    tcx: ctxt,
+    method_map: HashMap<node_id,method_map_entry>,
+    mode: ValueMode,
+}
+
+fn compute_modes_for_fn_args(callee_id: node_id,
+                             args: &[@expr],
+                             &&cx: VisitContext,
+                             v: vt<VisitContext>) {
+    let arg_tys = ty::ty_fn_args(ty::node_id_to_type(cx.tcx, callee_id));
+    for vec::each2(args, arg_tys) |arg, arg_ty| {
+        match ty::resolved_mode(cx.tcx, arg_ty.mode) {
+            by_ref => {
+                let arg_cx = VisitContext { mode: ReadValue, ..cx };
+                compute_modes_for_expr(*arg, arg_cx, v);
+            }
+            by_val | by_move | by_copy => compute_modes_for_expr(*arg, cx, v)
+        }
+    }
+}
+
+fn record_mode_for_expr(expr: @expr, &&cx: VisitContext) {
+    match cx.mode {
+        ReadValue | CopyValue => {
+            cx.tcx.value_modes.insert(expr.id, cx.mode);
+        }
+        MoveValue => {
+            // This is, contextually, a move, but if this expression
+            // is implicitly copyable it's cheaper to copy.
+            let e_ty = ty::expr_ty(cx.tcx, expr);
+            if ty::type_implicitly_moves(cx.tcx, e_ty) {
+                cx.tcx.value_modes.insert(expr.id, MoveValue);
+            } else {
+                cx.tcx.value_modes.insert(expr.id, CopyValue);
+            }
+        }
+    }
+}
+
+fn compute_modes_for_expr(expr: @expr,
+                          &&cx: VisitContext,
+                          v: vt<VisitContext>) {
+    // Adjust the mode if there was an implicit reference here.
+    let cx = match cx.tcx.adjustments.find(expr.id) {
+        None => cx,
+        Some(adjustment) => {
+            if adjustment.autoref.is_some() {
+                VisitContext { mode: ReadValue, ..cx }
+            } else {
+                cx
+            }
+        }
+    };
+
+    match expr.node {
+        expr_call(callee, args, _) => {
+            let callee_cx = VisitContext { mode: ReadValue, ..cx };
+            compute_modes_for_expr(callee, callee_cx, v);
+            compute_modes_for_fn_args(callee.id, args, cx, v);
+        }
+        expr_path(*) => {
+            record_mode_for_expr(expr, cx);
+        }
+        expr_copy(expr) => {
+            let callee_cx = VisitContext { mode: CopyValue, ..cx };
+            compute_modes_for_expr(expr, callee_cx, v);
+        }
+        expr_method_call(callee, _, _, args, _) => {
+            // The LHS of the dot may or may not result in a move, depending
+            // on the method map entry.
+            let callee_mode;
+            match cx.method_map.find(expr.id) {
+                Some(ref method_map_entry) => {
+                    match method_map_entry.explicit_self {
+                        sty_uniq(_) | sty_value => callee_mode = MoveValue,
+                        _ => callee_mode = ReadValue
+                    }
+                }
+                None => {
+                    cx.tcx.sess.span_bug(expr.span, ~"no method map entry");
+                }
+            }
+
+            let callee_cx = VisitContext { mode: callee_mode, ..cx };
+            compute_modes_for_expr(callee, callee_cx, v);
+
+            compute_modes_for_fn_args(expr.callee_id, args, cx, v);
+        }
+        expr_binary(_, lhs, rhs) | expr_assign_op(_, lhs, rhs) => {
+            // The signatures of these take their arguments by-ref, so they
+            // don't copy or move.
+            let arg_cx = VisitContext { mode: ReadValue, ..cx };
+            compute_modes_for_expr(lhs, arg_cx, v);
+            compute_modes_for_expr(rhs, arg_cx, v);
+        }
+        expr_addr_of(_, arg) => {
+            // Takes its argument by-ref, so it doesn't copy or move.
+            let arg_cx = VisitContext { mode: ReadValue, ..cx };
+            compute_modes_for_expr(arg, arg_cx, v);
+        }
+        expr_unary(unop, arg) => {
+            // Ditto.
+            let arg_cx = VisitContext { mode: ReadValue, ..cx };
+            compute_modes_for_expr(arg, arg_cx, v);
+
+            match unop {
+                deref => {
+                    // This is an lvalue, so it needs a value mode recorded
+                    // for it.
+                    record_mode_for_expr(expr, cx);
+                }
+                box(_) | uniq(_) | not | neg => {}
+            }
+        }
+        expr_field(arg, _, _) => {
+            let arg_cx = VisitContext { mode: ReadValue, ..cx };
+            compute_modes_for_expr(arg, arg_cx, v);
+
+            record_mode_for_expr(expr, cx);
+        }
+        expr_assign(lhs, rhs) => {
+            // The signatures of these take their arguments by-ref, so they
+            // don't copy or move.
+            let arg_cx = VisitContext { mode: ReadValue, ..cx };
+            compute_modes_for_expr(lhs, arg_cx, v);
+            compute_modes_for_expr(rhs, cx, v);
+        }
+        expr_swap(lhs, rhs) => {
+            let arg_cx = VisitContext { mode: ReadValue, ..cx };
+            compute_modes_for_expr(lhs, arg_cx, v);
+            compute_modes_for_expr(rhs, arg_cx, v);
+        }
+        expr_index(lhs, rhs) => {
+            let lhs_cx = VisitContext { mode: ReadValue, ..cx };
+            compute_modes_for_expr(lhs, lhs_cx, v);
+            let rhs_cx = VisitContext { mode: MoveValue, ..cx };
+            compute_modes_for_expr(rhs, rhs_cx, v);
+
+            record_mode_for_expr(expr, cx);
+        }
+        expr_paren(arg) => {
+            compute_modes_for_expr(arg, cx, v);
+            record_mode_for_expr(expr, cx);
+        }
+        _ => {
+            // XXX: Spell out every expression above so when we add them we
+            // don't forget to update this file.
+            visit::visit_expr(expr, cx, v)
+        }
+    }
+}
+
+pub fn compute_modes(tcx: ctxt, method_map: method_map, crate: @crate) {
+    let visitor = visit::mk_vt(@{
+        visit_expr: compute_modes_for_expr,
+        .. *visit::default_visitor()
+    });
+    let callee_cx = VisitContext {
+        tcx: tcx,
+        method_map: method_map,
+        mode: MoveValue
+    };
+    visit::visit_crate(*crate, callee_cx, visitor);
+}
+

src/librustc/middle/trans/closure.rs

@@ -270,7 +270,7 @@ fn build_closure(bcx0: block,
     let mut env_vals = ~[];
     for vec::each(cap_vars) |cap_var| {
         debug!("Building closure: captured variable %?", *cap_var);
-        let datum = expr::trans_local_var(bcx, cap_var.def);
+        let datum = expr::trans_local_var(bcx, cap_var.def, None);
         match cap_var.mode {
             capture::cap_ref => {
                 assert proto == ast::ProtoBorrowed;

src/librustc/middle/trans/datum.rs

@@ -509,13 +509,17 @@ impl Datum {
         }
     }
 
-    fn GEPi(bcx: block, ixs: &[uint], ty: ty::t) -> Datum {
+    fn GEPi(bcx: block,
+            ixs: &[uint],
+            ty: ty::t,
+            source: DatumSource)
+         -> Datum {
         let base_val = self.to_ref_llval(bcx);
         Datum {
             val: GEPi(bcx, base_val, ixs),
             mode: ByRef,
             ty: ty,
-            source: FromLvalue
+            source: source
         }
     }
 

src/librustc/middle/trans/expr.rs

@@ -121,6 +121,7 @@ use util::ppaux::ty_to_str;
 use util::common::indenter;
 use ty::{AutoPtr, AutoBorrowVec, AutoBorrowFn};
 use callee::{AutorefArg, DoAutorefArg, DontAutorefArg};
+use middle::ty::MoveValue;
 
 // The primary two functions for translating expressions:
 export trans_to_datum, trans_into;
@@ -736,7 +737,7 @@ fn trans_lvalue_unadjusted(bcx: block, expr: @ast::expr) -> DatumBlock {
                 return trans_def_lvalue(bcx, expr, bcx.def(expr.id));
             }
             ast::expr_field(base, ident, _) => {
-                return trans_rec_field(bcx, base, ident);
+                return trans_rec_field(bcx, base, ident, expr.id);
             }
             ast::expr_index(base, idx) => {
                 return trans_index(bcx, expr, base, idx);
@@ -756,8 +757,10 @@ fn trans_lvalue_unadjusted(bcx: block, expr: @ast::expr) -> DatumBlock {
     }
 }
 
-fn trans_def_lvalue(bcx: block, ref_expr: @ast::expr,
-                    def: ast::def) -> DatumBlock {
+fn trans_def_lvalue(bcx: block,
+                    ref_expr: @ast::expr,
+                    def: ast::def)
+                 -> DatumBlock {
     let _icx = bcx.insn_ctxt("trans_def_lvalue");
     let ccx = bcx.ccx();
     match def {
@@ -779,17 +782,21 @@ fn trans_def_lvalue(bcx: block, ref_expr: @ast::expr,
         _ => {
             DatumBlock {
                 bcx: bcx,
-                datum: trans_local_var(bcx, def)
+                datum: trans_local_var(bcx, def, Some(ref_expr.id))
             }
         }
     }
 }
 
-fn trans_local_var(bcx: block, def: ast::def) -> Datum {
+fn trans_local_var(bcx: block,
+                   def: ast::def,
+                   expr_id_opt: Option<ast::node_id>)
+                -> Datum {
     let _icx = bcx.insn_ctxt("trans_local_var");
 
     return match def {
         ast::def_upvar(nid, _, _, _) => {
+            // Can't move upvars, so this is never a FromLvalueLastUse.
             let local_ty = node_id_type(bcx, nid);
             match bcx.fcx.llupvars.find(nid) {
                 Some(val) => {
@@ -807,10 +814,10 @@ fn trans_local_var(bcx: block, def: ast::def) -> Datum {
             }
         }
         ast::def_arg(nid, _) => {
-            take_local(bcx, bcx.fcx.llargs, nid)
+            take_local(bcx, bcx.fcx.llargs, nid, expr_id_opt)
         }
         ast::def_local(nid, _) | ast::def_binding(nid, _) => {
-            take_local(bcx, bcx.fcx.lllocals, nid)
+            take_local(bcx, bcx.fcx.lllocals, nid, expr_id_opt)
         }
         ast::def_self(nid) => {
             let self_info: ValSelfData = match bcx.fcx.llself {
@@ -832,7 +839,7 @@ fn trans_local_var(bcx: block, def: ast::def) -> Datum {
                 val: casted_val,
                 ty: self_info.t,
                 mode: ByRef,
-                source: FromLvalue
+                source: source_from_opt_lvalue_type(bcx.tcx(), expr_id_opt)
             }
         }
         _ => {
@@ -843,8 +850,8 @@ fn trans_local_var(bcx: block, def: ast::def) -> Datum {
 
     fn take_local(bcx: block,
                   table: HashMap<ast::node_id, local_val>,
-                  nid: ast::node_id) -> Datum {
-
+                  nid: ast::node_id,
+                  expr_id_opt: Option<ast::node_id>) -> Datum {
         let (v, mode) = match table.find(nid) {
             Some(local_mem(v)) => (v, ByRef),
             Some(local_imm(v)) => (v, ByValue),
@@ -858,7 +865,12 @@ fn trans_local_var(bcx: block, def: ast::def) -> Datum {
         debug!("take_local(nid=%?, v=%s, mode=%?, ty=%s)",
                nid, bcx.val_str(v), mode, bcx.ty_to_str(ty));
 
-        Datum { val: v, ty: ty, mode: mode, source: FromLvalue }
+        Datum {
+            val: v,
+            ty: ty,
+            mode: mode,
+            source: source_from_opt_lvalue_type(bcx.tcx(), expr_id_opt)
+        }
     }
 }
 
@@ -943,7 +955,8 @@ fn with_field_tys<R>(tcx: ty::ctxt,
 
 fn trans_rec_field(bcx: block,
                    base: @ast::expr,
-                   field: ast::ident) -> DatumBlock {
+                   field: ast::ident,
+                   expr_id: ast::node_id) -> DatumBlock {
     let mut bcx = bcx;
     let _icx = bcx.insn_ctxt("trans_rec_field");
 
@@ -951,12 +964,30 @@ fn trans_rec_field(bcx: block,
     do with_field_tys(bcx.tcx(), base_datum.ty, None) |_dtor, field_tys| {
         let ix = ty::field_idx_strict(bcx.tcx(), field, field_tys);
         DatumBlock {
-            datum: base_datum.GEPi(bcx, [0u, 0u, ix], field_tys[ix].mt.ty),
+            datum: base_datum.GEPi(bcx,
+                                   [0u, 0u, ix],
+                                   field_tys[ix].mt.ty,
+                                   source_from_opt_lvalue_type(
+                                        bcx.tcx(), Some(expr_id))),
             bcx: bcx
         }
     }
 }
 
+fn source_from_opt_lvalue_type(tcx: ty::ctxt,
+                               expr_id_opt: Option<ast::node_id>)
+                            -> DatumSource {
+    match expr_id_opt {
+        None => FromLvalue,
+        Some(expr_id) => {
+            match tcx.value_modes.find(expr_id) {
+                Some(MoveValue) => FromLastUseLvalue,
+                Some(_) | None => FromLvalue,
+            }
+        }
+    }
+}
+
 fn trans_index(bcx: block,
                index_expr: @ast::expr,
                base: @ast::expr,
@@ -1010,8 +1041,11 @@ fn trans_index(bcx: block,
     let elt = PointerCast(bcx, elt, T_ptr(vt.llunit_ty));
     return DatumBlock {
         bcx: bcx,
-        datum: Datum {val: elt, ty: vt.unit_ty,
-                      mode: ByRef, source: FromLvalue}
+        datum: Datum {val: elt,
+                      ty: vt.unit_ty,
+                      mode: ByRef,
+                      source: source_from_opt_lvalue_type(
+                            bcx.tcx(), Some(index_expr.id))}
     };
 }
 
@@ -1101,7 +1135,10 @@ fn trans_rec_or_struct(bcx: block,
                 if !fields.any(|f| f.node.ident == field_ty.ident) {
                     let dest = GEPi(bcx, addr, struct_field(i));
                     let base_field =
-                        base_datum.GEPi(bcx, struct_field(i), field_ty.mt.ty);
+                        base_datum.GEPi(bcx,
+                                        struct_field(i),
+                                        field_ty.mt.ty,
+                                        FromLvalue);
                     bcx = base_field.store_to(bcx, INIT, dest);
                 }
             }

src/librustc/middle/trans/foreign.rs

@@ -65,7 +65,7 @@ fn is_sse(++c: x86_64_reg_class) -> bool {
     };
 }
 
-fn is_ymm(cls: ~[x86_64_reg_class]) -> bool {
+fn is_ymm(cls: &[x86_64_reg_class]) -> bool {
     let len = vec::len(cls);
     return (len > 2u &&
          is_sse(cls[0]) &&
@@ -136,13 +136,13 @@ fn classify_ty(ty: TypeRef) -> ~[x86_64_reg_class] {
         };
     }
 
-    fn all_mem(cls: ~[mut x86_64_reg_class]) {
+    fn all_mem(cls: &[mut x86_64_reg_class]) {
         for uint::range(0, cls.len()) |i| {
             cls[i] = memory_class;
         }
     }
 
-    fn unify(cls: ~[mut x86_64_reg_class],
+    fn unify(cls: &[mut x86_64_reg_class],
              i: uint,
              newv: x86_64_reg_class) {
         if cls[i] == newv {
@@ -167,8 +167,8 @@ fn classify_ty(ty: TypeRef) -> ~[x86_64_reg_class] {
         }
     }
 
-    fn classify_struct(tys: ~[TypeRef],
-                       cls: ~[mut x86_64_reg_class], i: uint,
+    fn classify_struct(tys: &[TypeRef],
+                       cls: &[mut x86_64_reg_class], i: uint,
                        off: uint) {
         if vec::is_empty(tys) {
             classify(T_i64(), cls, i, off);
@@ -183,7 +183,7 @@ fn classify_ty(ty: TypeRef) -> ~[x86_64_reg_class] {
     }
 
     fn classify(ty: TypeRef,
-                cls: ~[mut x86_64_reg_class], ix: uint,
+                cls: &[mut x86_64_reg_class], ix: uint,
                 off: uint) {
         let t_align = ty_align(ty);
         let t_size = ty_size(ty);
@@ -231,7 +231,7 @@ fn classify_ty(ty: TypeRef) -> ~[x86_64_reg_class] {
         }
     }
 
-    fn fixup(ty: TypeRef, cls: ~[mut x86_64_reg_class]) {
+    fn fixup(ty: TypeRef, cls: &[mut x86_64_reg_class]) {
         let mut i = 0u;
         let llty = llvm::LLVMGetTypeKind(ty) as int;
         let e = vec::len(cls);
@@ -289,8 +289,8 @@ fn classify_ty(ty: TypeRef) -> ~[x86_64_reg_class] {
     return vec::from_mut(move cls);
 }
 
-fn llreg_ty(cls: ~[x86_64_reg_class]) -> TypeRef {
-    fn llvec_len(cls: ~[x86_64_reg_class]) -> uint {
+fn llreg_ty(cls: &[x86_64_reg_class]) -> TypeRef {
+    fn llvec_len(cls: &[x86_64_reg_class]) -> uint {
         let mut len = 1u;
         for vec::each(cls) |c| {
             if *c != sseup_class {
@@ -342,7 +342,7 @@ type x86_64_tys = {
     sret: bool
 };
 
-fn x86_64_tys(atys: ~[TypeRef],
+fn x86_64_tys(atys: &[TypeRef],
               rty: TypeRef,
               ret_def: bool) -> x86_64_tys {
     fn is_reg_ty(ty: TypeRef) -> bool {
@@ -355,18 +355,18 @@ fn x86_64_tys(atys: ~[TypeRef],
         };
     }
 
-    fn is_pass_byval(cls: ~[x86_64_reg_class]) -> bool {
+    fn is_pass_byval(cls: &[x86_64_reg_class]) -> bool {
         return cls[0] == memory_class ||
             cls[0] == x87_class ||
             cls[0] == complex_x87_class;
     }
 
-    fn is_ret_bysret(cls: ~[x86_64_reg_class]) -> bool {
+    fn is_ret_bysret(cls: &[x86_64_reg_class]) -> bool {
         return cls[0] == memory_class;
     }
 
     fn x86_64_ty(ty: TypeRef,
-                 is_mem_cls: fn(cls: ~[x86_64_reg_class]) -> bool,
+                 is_mem_cls: fn(cls: &[x86_64_reg_class]) -> bool,
                  attr: Attribute) -> (x86_64_llty, Option<Attribute>) {
         let mut cast = false;
         let mut ty_attr = option::None;

src/librustc/middle/ty.rs

@@ -117,6 +117,7 @@ export ty_uint, mk_uint, mk_mach_uint;
 export ty_uniq, mk_uniq, mk_imm_uniq, type_is_unique_box;
 export ty_infer, mk_infer, type_is_ty_var, mk_var, mk_int_var, mk_float_var;
 export InferTy, TyVar, IntVar, FloatVar;
+export ValueMode, ReadValue, CopyValue, MoveValue;
 export ty_self, mk_self, type_has_self;
 export ty_class;
 export Region, bound_region, encl_region;
@@ -134,6 +135,7 @@ export ty_region;
 export Kind, kind_implicitly_copyable, kind_send_copy, kind_copyable;
 export kind_noncopyable, kind_const;
 export kind_can_be_copied, kind_can_be_sent, kind_can_be_implicitly_copied;
+export type_implicitly_moves;
 export kind_is_safe_for_default_mode;
 export kind_is_owned;
 export meta_kind, kind_lteq, type_kind;
@@ -251,6 +253,15 @@ type field_ty = {
   mutability: ast::class_mutability
 };
 
+/// How an lvalue is to be used.
+#[auto_serialize]
+#[auto_deserialize]
+pub enum ValueMode {
+    ReadValue,  // Non-destructively read the value; do not copy or move.
+    CopyValue,  // Copy the value.
+    MoveValue,  // Move the value.
+}
+
 // Contains information needed to resolve types and (in the future) look up
 // the types of AST nodes.
 type creader_cache_key = {cnum: int, pos: uint, len: uint};
@@ -429,7 +440,10 @@ type ctxt =
       destructor_for_type: HashMap<ast::def_id, ast::def_id>,
 
       // A method will be in this list if and only if it is a destructor.
-      destructors: HashMap<ast::def_id, ()>
+      destructors: HashMap<ast::def_id, ()>,
+
+      // Records the value mode (read, copy, or move) for every value.
+      value_modes: HashMap<ast::node_id, ValueMode>,
       };
 
 enum tbox_flag {
@@ -968,7 +982,8 @@ fn mk_ctxt(s: session::Session,
       automatically_derived_methods: HashMap(),
       automatically_derived_methods_for_impl: HashMap(),
       destructor_for_type: HashMap(),
-      destructors: HashMap()}
+      destructors: HashMap(),
+      value_modes: HashMap()}
 }
 
 
@@ -2258,6 +2273,11 @@ fn type_kind(cx: ctxt, ty: t) -> Kind {
     return result;
 }
 
+fn type_implicitly_moves(cx: ctxt, ty: t) -> bool {
+    let kind = type_kind(cx, ty);
+    !(kind_can_be_copied(kind) && kind_can_be_implicitly_copied(kind))
+}
+
 /// gives a rough estimate of how much space it takes to represent
 /// an instance of `ty`.  Used for the mode transition.
 fn type_size(cx: ctxt, ty: t) -> uint {

src/librustc/rustc.rc

@@ -181,6 +181,8 @@ mod middle {
     #[legacy_exports]
     #[path = "middle/privacy.rs"]
     mod privacy;
+    #[path = "middle/mode.rs"]
+    mod mode;
 }
 
 mod front {

src/libstd/net_tcp.rs

@@ -610,9 +610,9 @@ fn listen_common(host_ip: ip::IpAddr, port: uint, backlog: uint,
         kill_ch: kill_ch,
         on_connect_cb: move on_connect_cb,
         iotask: iotask,
-        ipv6: match host_ip {
-            ip::Ipv4(_) => { false }
-            ip::Ipv6(_) => { true }
+        ipv6: match &host_ip {
+            &ip::Ipv4(_) => { false }
+            &ip::Ipv6(_) => { true }
         },
         mut active: true
     };

src/libsyntax/ext/tt/macro_parser.rs

@@ -100,8 +100,8 @@ enum matcher_pos_up { /* to break a circularity */
 }
 
 fn is_some(&&mpu: matcher_pos_up) -> bool {
-    match mpu {
-      matcher_pos_up(None) => false,
+    match &mpu {
+      &matcher_pos_up(None) => false,
       _ => true
     }
 }

src/test/auxiliary/moves_based_on_type_lib.rs

@@ -0,0 +1,15 @@
+#[crate_type="lib"];
+
+pub struct S {
+    x: int,
+    drop {
+        io::println("goodbye");
+    }
+}
+
+pub fn f() {
+    let x = S { x: 1 };
+    let y = x;
+    let z = y;
+}
+

src/test/compile-fail/use-after-move-based-on-type.rs

@@ -0,0 +1,6 @@
+fn main() {
+    let x = ~"Hello!";
+    let _y = x;
+    io::println(x); //~ ERROR use of moved variable
+}
+

src/test/run-pass/moves-based-on-type-cross-crate.rs

@@ -0,0 +1,9 @@
+// xfail-fast
+// aux-build:moves_based_on_type_lib.rs
+
+extern mod moves_based_on_type_lib;
+use moves_based_on_type_lib::f;
+
+fn main() {
+    f();
+}