Add representation for by-ref let bindings

Issue #918

Author: marijnh

src/comp/middle/alias.rs

@@ -144,7 +144,8 @@ fn visit_decl(cx: @ctx, d: @ast::decl, sc: scope, v: vt<scope>) {
     visit::visit_decl(d, sc, v);
     alt d.node {
       ast::decl_local(locs) {
-        for loc: @ast::local in locs {
+        // FIXME check that init is lvalue
+        for (style, loc) in locs {
             alt loc.node.init {
               some(init) {
                 if init.op == ast::init_move {

src/comp/middle/mut.rs

@@ -142,7 +142,7 @@ fn visit_decl(cx: @ctx, d: @decl, e: (), v: visit::vt<()>) {
     visit::visit_decl(d, e, v);
     alt d.node {
       decl_local(locs) {
-        for loc: @local in locs {
+        for (_, loc) in locs {
             alt loc.node.init {
               some(init) {
                 if init.op == init_move { check_move_rhs(cx, init.expr); }

src/comp/middle/resolve.rs

@@ -371,7 +371,7 @@ fn visit_decl_with_scope(d: @decl, sc: scopes, v: vt<scopes>) {
         };
     alt d.node {
       decl_local(locs) {
-        for loc in locs { v.visit_local(loc, sc, v);; *loc_pos += 1u; }
+        for (_, loc) in locs { v.visit_local(loc, sc, v);; *loc_pos += 1u; }
       }
       decl_item(it) { v.visit_item(it, sc, v); }
     }
@@ -797,7 +797,7 @@ fn lookup_in_block(name: ident, b: ast::blk_, pos: uint, loc_pos: uint,
                     let j = vec::len(locs);
                     while j > 0u {
                         j -= 1u;
-                        let loc = locs[j];
+                        let (_, loc) = locs[j];
                         if ns == ns_value && (i < pos || j < loc_pos) {
                             alt lookup_in_pat(name, loc.node.pat) {
                               some(did) { ret some(ast::def_local(did)); }
@@ -1315,7 +1315,7 @@ fn check_block(e: @env, b: ast::blk, x: (), v: vt<()>) {
             alt d.node {
               ast::decl_local(locs) {
                 let local_values = checker(*e, "value");
-                for loc in locs {
+                for (_, loc) in locs {
                     for each p in ast_util::pat_bindings(loc.node.pat) {
                         let ident = alt p.node { pat_bind(n) { n } };
                         add_name(local_values, p.span, ident);

src/comp/middle/trans.rs

@@ -4538,7 +4538,7 @@ fn trans_stmt(cx: @block_ctxt, s: ast::stmt) -> result {
       ast::stmt_decl(d, _) {
         alt d.node {
           ast::decl_local(locals) {
-            for local: @ast::local in locals {
+            for (_, local) in locals {
                 bcx = init_local(bcx, local).bcx;
             }
           }
@@ -4654,7 +4654,7 @@ iter block_locals(b: ast::blk) -> @ast::local {
           ast::stmt_decl(d, _) {
             alt d.node {
               ast::decl_local(locals) {
-                for local: @ast::local in locals { put local; }
+                for (_, local) in locals { put local; }
               }
               _ {/* fall through */ }
             }

src/comp/middle/tstate/auxiliary.rs

@@ -1063,8 +1063,10 @@ fn local_to_bindings(loc: @local) -> binding {
     {lhs: lhs, rhs: loc.node.init}
 }
 
-fn locals_to_bindings(locals: [@local]) -> [binding] {
-    vec::map(local_to_bindings, locals)
+fn locals_to_bindings(locals: [(let_style, @local)]) -> [binding] {
+    let rslt = [];
+    for (_, loc) in locals { rslt += [local_to_bindings(loc)]; }
+    ret rslt;
 }
 
 fn callee_modes(fcx: fn_ctxt, callee: node_id) -> [ty::mode] {

src/comp/middle/tstate/pre_post_conditions.rs

@@ -572,7 +572,7 @@ fn find_pre_post_stmt(fcx: fn_ctxt, s: stmt) {
           decl_local(alocals) {
             let e_pp;
             let prev_pp = empty_pre_post(num_constraints(fcx.enclosing));
-            for alocal: @local in alocals {
+            for (_, alocal) in alocals {
                 alt alocal.node.init {
                   some(an_init) {
                     /* LHS always becomes initialized,

src/comp/middle/typeck.rs

@@ -2418,7 +2418,7 @@ fn check_stmt(fcx: @fn_ctxt, stmt: @ast::stmt) -> bool {
         node_id = id;
         alt decl.node {
           ast::decl_local(ls) {
-            for l: @ast::local in ls { bot |= check_decl_local(fcx, l); }
+            for (_, l) in ls { bot |= check_decl_local(fcx, l); }
           }
           ast::decl_item(_) {/* ignore for now */ }
         }

src/comp/syntax/ast.rs

@@ -149,7 +149,9 @@ type local = spanned<local_>;
 
 type decl = spanned<decl_>;
 
-tag decl_ { decl_local([@local]); decl_item(@item); }
+tag let_style { let_copy; let_ref; }
+
+tag decl_ { decl_local([(let_style, @local)]); decl_item(@item); }
 
 type arm = {pats: [@pat], guard: option::t<@expr>, body: blk};
 

src/comp/syntax/fold.rs

@@ -296,7 +296,10 @@ fn noop_fold_pat(p: pat_, fld: ast_fold) -> pat_ {
 
 fn noop_fold_decl(d: decl_, fld: ast_fold) -> decl_ {
     ret alt d {
-          decl_local(ls) { decl_local(vec::map(fld.fold_local, ls)) }
+          decl_local(ls) {
+            decl_local(vec::map({|l| let (st, lc) = l;
+                                 (st, fld.fold_local(lc))}, ls))
+          }
           decl_item(it) { decl_item(fld.fold_item(it)) }
         }
 }

src/comp/syntax/parse/parser.rs

@@ -1505,11 +1505,13 @@ fn parse_local(p: parser, allow_init: bool) -> @ast::local {
 }
 
 fn parse_let(p: parser) -> @ast::decl {
+    fn parse_let_style(p: parser) -> ast::let_style {
+        eat(p, token::BINOP(token::AND)) ? ast::let_ref : ast::let_copy
+    }
     let lo = p.get_lo_pos();
-    let locals = [parse_local(p, true)];
-    while p.peek() == token::COMMA {
-        p.bump();
-        locals += [parse_local(p, true)];
+    let locals = [(parse_let_style(p), parse_local(p, true))];
+    while eat(p, token::COMMA) {
+        locals += [(parse_let_style(p), parse_local(p, true))];
     }
     ret @spanned(lo, p.get_last_hi_pos(), ast::decl_local(locals));
 }

src/comp/syntax/print/pprust.rs

@@ -1024,8 +1024,10 @@ fn print_decl(s: ps, decl: @ast::decl) {
         space_if_not_bol(s);
         ibox(s, indent_unit);
         word_nbsp(s, "let");
-        fn print_local(s: ps, loc: @ast::local) {
+        fn print_local(s: ps, loc_st: (ast::let_style, @ast::local)) {
+            let (st, loc) = loc_st;
             ibox(s, indent_unit);
+            if st == ast::let_ref { word(s.s, "&"); }
             print_local_decl(s, loc);
             end(s);
             alt loc.node.init {

src/comp/syntax/visit.rs

@@ -212,7 +212,7 @@ fn visit_stmt<E>(s: @stmt, e: E, v: vt<E>) {
 fn visit_decl<E>(d: @decl, e: E, v: vt<E>) {
     alt d.node {
       decl_local(locs) {
-        for loc: @ast::local in locs { v.visit_local(loc, e, v); }
+        for (_, loc) in locs { v.visit_local(loc, e, v); }
       }
       decl_item(it) { v.visit_item(it, e, v); }
     }