Add operator 'copy', translates as fall-through.

Author: graydon

src/comp/middle/trans.rs

@@ -5052,6 +5052,10 @@ fn trans_expr_out(cx: &@block_ctxt, e: &@ast::expr, output: out_method) ->
         sub.bcx.build.Br(next_cx.llbb);
         ret rslt(next_cx, sub.val);
       }
+      ast::expr_copy(a) {
+        // FIXME: this has more-subtle semantics than just "fall through".
+        ret trans_expr_out(cx, a, output);
+      }
       ast::expr_move(dst, src) {
         let lhs_res = trans_lval(cx, dst);
         assert (lhs_res.is_mem);

src/comp/middle/trans_alt.rs

@@ -517,12 +517,13 @@ fn trans_alt(cx: &@block_ctxt, expr: &@ast::expr, arms: &[ast::arm],
 
 // Not alt-related, but similar to the pattern-munging code above
 fn bind_irrefutable_pat(bcx: @block_ctxt, pat: &@ast::pat, val: ValueRef,
-                        table: hashmap[ast::node_id, ValueRef], copy: bool)
+                        table: hashmap[ast::node_id, ValueRef],
+                        make_copy: bool)
     -> @block_ctxt {
     let ccx = bcx.fcx.lcx.ccx;
     alt pat.node {
       ast::pat_bind(_) {
-        if copy {
+        if make_copy {
             let ty = ty::node_id_to_monotype(ccx.tcx, pat.id);
             let llty = trans::type_of(ccx, pat.span, ty);
             let alloc = trans::alloca(bcx, llty);
@@ -541,7 +542,8 @@ fn bind_irrefutable_pat(bcx: @block_ctxt, pat: &@ast::pat, val: ValueRef,
         let args = extract_variant_args(bcx, pat.id, vdefs, val);
         let i = 0;
         for argval: ValueRef in args.vals {
-            bcx = bind_irrefutable_pat(bcx, sub.(i), argval, table, copy);
+            bcx = bind_irrefutable_pat(bcx, sub.(i), argval, table,
+                                       make_copy);
             i += 1;
         }
       }
@@ -553,15 +555,15 @@ fn bind_irrefutable_pat(bcx: @block_ctxt, pat: &@ast::pat, val: ValueRef,
             let ix: uint =
                 ty::field_idx(ccx.sess, pat.span, f.ident, rec_fields);
             let r = trans::GEP_tup_like(bcx, rec_ty, val, ~[0, ix as int]);
-            bcx = bind_irrefutable_pat(r.bcx, f.pat, r.val, table, copy);
+            bcx = bind_irrefutable_pat(r.bcx, f.pat, r.val, table, make_copy);
         }
       }
       ast::pat_tup(elems) {
         let tup_ty = ty::node_id_to_monotype(ccx.tcx, pat.id);
         let i = 0u;
         for elem in elems {
             let r = trans::GEP_tup_like(bcx, tup_ty, val, ~[0, i as int]);
-            bcx = bind_irrefutable_pat(r.bcx, elem, r.val, table, copy);
+            bcx = bind_irrefutable_pat(r.bcx, elem, r.val, table, make_copy);
             i += 1u;
         }
       }

src/comp/middle/tstate/pre_post_conditions.rs

@@ -406,6 +406,10 @@ fn find_pre_post_expr(fcx: &fn_ctxt, e: @expr) {
       expr_tup(elts) {
         find_pre_post_exprs(fcx, elts, e.id);
       }
+      expr_copy(a) {
+        find_pre_post_expr(fcx, a);
+        copy_pre_post(fcx.ccx, e.id, a);
+      }
       expr_move(lhs, rhs) { handle_update(fcx, e, lhs, rhs, oper_move); }
       expr_swap(lhs, rhs) { handle_update(fcx, e, lhs, rhs, oper_swap); }
       expr_assign(lhs, rhs) { handle_update(fcx, e, lhs, rhs, oper_assign); }

src/comp/middle/tstate/states.rs

@@ -393,6 +393,9 @@ fn find_pre_post_state_expr(fcx: &fn_ctxt, pres: &prestate, e: @expr) ->
                                                      ivec::len(elts)),
                                       elts, return);
       }
+      expr_copy(a) {
+        ret find_pre_post_state_sub(fcx, pres, a, e.id, none);
+      }
       expr_move(lhs, rhs) {
         ret find_pre_post_state_two(fcx, pres, lhs, rhs, e.id, oper_move);
       }

src/comp/middle/tstate/tritv.rs

@@ -204,8 +204,8 @@ fn tritv_copy(target: &t, source: &t) -> bool {
     let changed =
         !bitv::equal(target.uncertain, source.uncertain) ||
             !bitv::equal(target.val, source.val);
-    bitv::copy(target.uncertain, source.uncertain);
-    bitv::copy(target.val, source.val);
+    bitv::assign(target.uncertain, source.uncertain);
+    bitv::assign(target.val, source.val);
     ret changed;
 }
 

src/comp/middle/typeck.rs

@@ -1942,6 +1942,13 @@ fn check_expr_with_unifier(fcx: &@fn_ctxt, expr: &@ast::expr,
         bot = check_expr_with(fcx, e, ty::mk_bool(tcx));
         write::nil_ty(tcx, id);
       }
+      ast::expr_copy(a) {
+        bot = check_expr_with_unifier(fcx, a, unify, expected);
+        let tpot = ty::node_id_to_ty_param_substs_opt_and_ty(fcx.ccx.tcx,
+                                                             a.id);
+        write::ty_fixup(fcx, id, tpot);
+
+      }
       ast::expr_move(lhs, rhs) {
         require_impure(tcx.sess, fcx.purity, expr.span);
         bot = check_assignment(fcx, expr.span, lhs, rhs, id);

src/comp/syntax/ast.rs

@@ -317,6 +317,7 @@ tag expr_ {
      * FIXME: many of these @exprs should be constrained with
      * is_lval once we have constrained types working.
      */
+    expr_copy(@expr);
     expr_move(@expr, @expr);
     expr_assign(@expr, @expr);
     expr_swap(@expr, @expr);

src/comp/syntax/fold.rs

@@ -397,6 +397,9 @@ fn noop_fold_expr(e: &expr_, fld: ast_fold) -> expr_ {
           expr_move(el, er) {
             expr_move(fld.fold_expr(el), fld.fold_expr(er))
           }
+          expr_copy(e) {
+            expr_copy(fld.fold_expr(e))
+          }
           expr_assign(el, er) {
             expr_assign(fld.fold_expr(el), fld.fold_expr(er))
           }

src/comp/syntax/parse/parser.rs

@@ -180,6 +180,7 @@ fn bad_expr_word_table() -> hashmap[str, ()] {
     words.insert("log_err", ());
     words.insert("tag", ());
     words.insert("obj", ());
+    words.insert("copy", ());
     ret words;
 }
 
@@ -999,6 +1000,10 @@ fn parse_bottom_expr(p: &parser) -> @ast::expr {
         hi = e.span.hi;
         expect(p, token::RPAREN);
         ex = ast::expr_chan(e);
+    } else if (eat_word(p, "copy")) {
+        let e = parse_expr(p);
+        ex = ast::expr_copy(e);
+        hi = e.span.hi;
     } else if (eat_word(p, "self")) {
         log "parsing a self-call...";
         expect(p, token::DOT);

src/comp/syntax/print/pprust.rs

@@ -881,6 +881,10 @@ fn print_expr(s: &ps, expr: &@ast::expr) {
         ibox(s, 0u);
         print_block(s, blk);
       }
+      ast::expr_copy(e) {
+        word_space(s, "copy");
+        print_expr(s, e);
+      }
       ast::expr_move(lhs, rhs) {
         print_expr(s, lhs);
         space(s.s);

src/comp/syntax/visit.rs

@@ -299,6 +299,7 @@ fn visit_expr[E](ex: &@expr, e: &E, v: &vt[E]) {
       expr_fn(f) { v.visit_fn(f, ~[], ex.span, none, ex.id, e, v); }
       expr_block(b) { v.visit_block(b, e, v); }
       expr_assign(a, b) { v.visit_expr(b, e, v); v.visit_expr(a, e, v); }
+      expr_copy(a) { v.visit_expr(a, e, v); }
       expr_move(a, b) { v.visit_expr(b, e, v); v.visit_expr(a, e, v); }
       expr_swap(a, b) { v.visit_expr(a, e, v); v.visit_expr(b, e, v); }
       expr_assign_op(_, a, b) {

src/lib/bitv.rs

@@ -3,7 +3,7 @@ export t;
 export create;
 export union;
 export intersect;
-export copy;
+export assign;
 export clone;
 export get;
 export equal;
@@ -63,7 +63,10 @@ fn intersect(v0: &t, v1: &t) -> bool {
 
 fn right(w0: uint, w1: uint) -> uint { ret w1; }
 
-fn copy(v0: &t, v1: t) -> bool { let sub = right; ret process(sub, v0, v1); }
+fn assign(v0: &t, v1: t) -> bool {
+    let sub = right;
+    ret process(sub, v0, v1);
+}
 
 fn clone(v: t) -> t {
     let storage = ivec::init_elt_mut[uint](0u, v.nbits / uint_bits() + 1u);

src/test/run-pass/expr-copy.rs

@@ -0,0 +1,5 @@
+fn main() {
+    let x = 10;
+    let y = copy x;
+    log y;
+}