Add support for break and cont to rustc

Testing proper cleanup is hampered by
https://github.com/graydon/rust/issues/293

Author: marijnh

Diff for: src/comp/front/ast.rs

@@ -246,6 +246,8 @@ tag expr_ {
     expr_path(path, option.t[def], ann);
     expr_ext(path, vec[@expr], option.t[@expr], @expr, ann);
     expr_fail;
+    expr_break;
+    expr_cont;
     expr_ret(option.t[@expr]);
     expr_put(option.t[@expr]);
     expr_be(@expr);

Diff for: src/comp/front/lexer.rs

@@ -111,6 +111,8 @@ impure fn new_reader(io.reader rdr, str filename) -> reader
 
     keywords.insert("for", token.FOR);
     keywords.insert("each", token.EACH);
+    keywords.insert("break", token.BREAK);
+    keywords.insert("cont", token.CONT);
     keywords.insert("put", token.PUT);
     keywords.insert("ret", token.RET);
     keywords.insert("be", token.BE);

Diff for: src/comp/front/parser.rs

@@ -829,6 +829,16 @@ impure fn parse_bottom_expr(parser p) -> @ast.expr {
             }
         }
 
+        case (token.BREAK) {
+            p.bump();
+            ex = ast.expr_break;
+        }
+
+        case (token.CONT) {
+            p.bump();
+            ex = ast.expr_cont;
+        }
+
         case (token.PUT) {
             p.bump();
             alt (p.peek()) {

Diff for: src/comp/front/token.rs

@@ -74,6 +74,9 @@ tag token {
     ALT;
     CASE;
 
+    BREAK;
+    CONT;
+
     FAIL;
     DROP;
 
@@ -242,6 +245,9 @@ fn to_str(token t) -> str {
         case (ALT) { ret "alt"; }
         case (CASE) { ret "case"; }
 
+        case (BREAK) { ret "break"; }
+        case (CONT) { ret "cont"; }
+
         case (FAIL) { ret "fail"; }
         case (DROP) { ret "drop"; }
 

Diff for: src/comp/middle/fold.rs

@@ -170,6 +170,10 @@ type ast_fold[ENV] =
 
      (fn(&ENV e, &span sp) -> @expr)              fold_expr_fail,
 
+     (fn(&ENV e, &span sp) -> @expr)              fold_expr_break,
+
+     (fn(&ENV e, &span sp) -> @expr)              fold_expr_cont,
+
      (fn(&ENV e, &span sp,
          &option.t[@expr] rv) -> @expr)           fold_expr_ret,
 
@@ -695,6 +699,14 @@ fn fold_expr[ENV](&ENV env, ast_fold[ENV] fld, &@expr e) -> @expr {
             ret fld.fold_expr_fail(env_, e.span);
         }
 
+        case (ast.expr_break) {
+            ret fld.fold_expr_break(env_, e.span);
+        }
+
+        case (ast.expr_cont) {
+            ret fld.fold_expr_cont(env_, e.span);
+        }
+
         case (ast.expr_ret(?oe)) {
             auto oee = none[@expr];
             alt (oe) {
@@ -1266,6 +1278,14 @@ fn identity_fold_expr_fail[ENV](&ENV env, &span sp) -> @expr {
     ret @respan(sp, ast.expr_fail);
 }
 
+fn identity_fold_expr_break[ENV](&ENV env, &span sp) -> @expr {
+    ret @respan(sp, ast.expr_break);
+}
+
+fn identity_fold_expr_cont[ENV](&ENV env, &span sp) -> @expr {
+    ret @respan(sp, ast.expr_cont);
+}
+
 fn identity_fold_expr_ret[ENV](&ENV env, &span sp,
                                &option.t[@expr] rv) -> @expr {
     ret @respan(sp, ast.expr_ret(rv));
@@ -1565,6 +1585,8 @@ fn new_identity_fold[ENV]() -> ast_fold[ENV] {
          fold_expr_path   = bind identity_fold_expr_path[ENV](_,_,_,_,_),
          fold_expr_ext    = bind identity_fold_expr_ext[ENV](_,_,_,_,_,_,_),
          fold_expr_fail   = bind identity_fold_expr_fail[ENV](_,_),
+         fold_expr_break  = bind identity_fold_expr_break[ENV](_,_),
+         fold_expr_cont   = bind identity_fold_expr_cont[ENV](_,_),
          fold_expr_ret    = bind identity_fold_expr_ret[ENV](_,_,_),
          fold_expr_put    = bind identity_fold_expr_put[ENV](_,_,_),
          fold_expr_be     = bind identity_fold_expr_be[ENV](_,_,_),

Diff for: src/comp/middle/trans.rs

@@ -130,6 +130,7 @@ tag cleanup {
 
 tag block_kind {
     SCOPE_BLOCK;
+    LOOP_SCOPE_BLOCK(option.t[@block_ctxt], @block_ctxt);
     NON_SCOPE_BLOCK;
 }
 
@@ -990,7 +991,7 @@ fn trans_non_gc_free(@block_ctxt cx, ValueRef v) -> result {
 }
 
 fn find_scope_cx(@block_ctxt cx) -> @block_ctxt {
-    if (cx.kind == SCOPE_BLOCK) {
+    if (cx.kind != NON_SCOPE_BLOCK) {
         ret cx;
     }
     alt (cx.parent) {
@@ -3043,13 +3044,15 @@ fn trans_for(@block_ctxt cx,
              @ast.decl decl,
              @ast.expr seq,
              &ast.block body) -> result {
-
     fn inner(@block_ctxt cx,
              @ast.local local, ValueRef curr,
-             @ty.t t, ast.block body) -> result {
+             @ty.t t, ast.block body,
+             @block_ctxt outer_next_cx) -> result {
 
-        auto scope_cx = new_scope_block_ctxt(cx, "for loop scope");
         auto next_cx = new_sub_block_ctxt(cx, "next");
+        auto scope_cx =
+            new_loop_scope_block_ctxt(cx, option.some[@block_ctxt](next_cx),
+                                      outer_next_cx, "for loop scope");
 
         cx.build.Br(scope_cx.llbb);
         auto local_res = alloc_local(scope_cx, local);
@@ -3069,10 +3072,13 @@ fn trans_for(@block_ctxt cx,
         }
     }
 
+    auto next_cx = new_sub_block_ctxt(cx, "next");
     auto seq_ty = ty.expr_ty(seq);
     auto seq_res = trans_expr(cx, seq);
-    ret iter_sequence(seq_res.bcx, seq_res.val, seq_ty,
-                      bind inner(_, local, _, _, body));
+    auto it = iter_sequence(seq_res.bcx, seq_res.val, seq_ty,
+                            bind inner(_, local, _, _, body, next_cx));
+    it.bcx.build.Br(next_cx.llbb);
+    ret res(next_cx, it.val);
 }
 
 
@@ -3308,8 +3314,9 @@ fn trans_while(@block_ctxt cx, @ast.expr cond,
                &ast.block body) -> result {
 
     auto cond_cx = new_scope_block_ctxt(cx, "while cond");
-    auto body_cx = new_scope_block_ctxt(cx, "while loop body");
     auto next_cx = new_sub_block_ctxt(cx, "next");
+    auto body_cx = new_loop_scope_block_ctxt(cx, option.none[@block_ctxt],
+                                             next_cx, "while loop body");
 
     auto body_res = trans_block(body_cx, body);
     auto cond_res = trans_expr(cond_cx, cond);
@@ -3326,8 +3333,9 @@ fn trans_while(@block_ctxt cx, @ast.expr cond,
 fn trans_do_while(@block_ctxt cx, &ast.block body,
                   @ast.expr cond) -> result {
 
-    auto body_cx = new_scope_block_ctxt(cx, "do-while loop body");
     auto next_cx = new_sub_block_ctxt(cx, "next");
+    auto body_cx = new_loop_scope_block_ctxt(cx, option.none[@block_ctxt],
+                                             next_cx, "do-while loop body");
 
     auto body_res = trans_block(body_cx, body);
     auto cond_res = trans_expr(body_res.bcx, cond);
@@ -4599,6 +4607,14 @@ fn trans_expr(@block_ctxt cx, @ast.expr e) -> result {
             ret trans_check_expr(cx, a);
         }
 
+        case (ast.expr_break) {
+            ret trans_break(cx);
+        }
+
+        case (ast.expr_cont) {
+            ret trans_cont(cx);
+        }
+
         case (ast.expr_ret(?e)) {
             ret trans_ret(cx, e);
         }
@@ -4770,6 +4786,47 @@ fn trans_put(@block_ctxt cx, &option.t[@ast.expr] e) -> result {
     ret res(bcx, bcx.build.FastCall(llcallee, llargs));
 }
 
+fn trans_break_cont(@block_ctxt cx, bool to_end) -> result {
+    auto bcx = cx;
+    // Locate closest loop block, outputting cleanup as we go.
+    auto cleanup_cx = cx;
+    while (true) {
+        bcx = trans_block_cleanups(bcx, cleanup_cx);
+        alt (cleanup_cx.kind) {
+            case (LOOP_SCOPE_BLOCK(?_cont, ?_break)) {
+                if (to_end) {
+                    bcx.build.Br(_break.llbb);
+                } else {
+                    alt (_cont) {
+                        case (option.some[@block_ctxt](?_cont)) {
+                            bcx.build.Br(_cont.llbb);
+                        }
+                        case (_) {
+                            bcx.build.Br(cleanup_cx.llbb);
+                        }
+                    }
+                }
+                ret res(new_sub_block_ctxt(cx, "unreachable"), C_nil());
+            }
+            case (_) {
+                alt (cleanup_cx.parent) {
+                    case (parent_some(?cx)) { cleanup_cx = cx; }
+                }
+            }
+        }
+    }
+    ret res(cx, C_nil()); // Never reached. Won't compile otherwise.
+}
+
+fn trans_break(@block_ctxt cx) -> result {
+    ret trans_break_cont(cx, true);
+}
+
+fn trans_cont(@block_ctxt cx) -> result {
+    ret trans_break_cont(cx, false);
+}
+
+
 fn trans_ret(@block_ctxt cx, &option.t[@ast.expr] e) -> result {
     auto bcx = cx;
     auto val = C_nil();
@@ -5033,6 +5090,12 @@ fn new_scope_block_ctxt(@block_ctxt bcx, str n) -> @block_ctxt {
     ret new_block_ctxt(bcx.fcx, parent_some(bcx), SCOPE_BLOCK, n);
 }
 
+fn new_loop_scope_block_ctxt(@block_ctxt bcx, option.t[@block_ctxt] _cont,
+                             @block_ctxt _break, str n) -> @block_ctxt {
+    ret new_block_ctxt(bcx.fcx, parent_some(bcx),
+                       LOOP_SCOPE_BLOCK(_cont, _break), n);
+}
+
 // Use this when you're making a general CFG BB within a scope.
 fn new_sub_block_ctxt(@block_ctxt bcx, str n) -> @block_ctxt {
     ret new_block_ctxt(bcx.fcx, parent_some(bcx), NON_SCOPE_BLOCK, n);
@@ -5043,7 +5106,7 @@ fn trans_block_cleanups(@block_ctxt cx,
                         @block_ctxt cleanup_cx) -> @block_ctxt {
     auto bcx = cx;
 
-    if (cleanup_cx.kind != SCOPE_BLOCK) {
+    if (cleanup_cx.kind == NON_SCOPE_BLOCK) {
         check (_vec.len[cleanup](cleanup_cx.cleanups) == 0u);
     }
 

Diff for: src/comp/middle/typeck.rs

@@ -1413,6 +1413,8 @@ fn demand_expr_full(&@fn_ctxt fcx, @ty.t expected, @ast.expr e,
         }
         case (ast.expr_fail) { e_1 = e.node; }
         case (ast.expr_log(_)) { e_1 = e.node; }
+        case (ast.expr_break) { e_1 = e.node; }
+        case (ast.expr_cont) { e_1 = e.node; }
         case (ast.expr_ret(_)) { e_1 = e.node; }
         case (ast.expr_put(_)) { e_1 = e.node; }
         case (ast.expr_be(_)) { e_1 = e.node; }
@@ -1806,6 +1808,14 @@ fn check_expr(&@fn_ctxt fcx, @ast.expr expr) -> @ast.expr {
             ret expr;
         }
 
+        case (ast.expr_break) {
+            ret expr;
+        }
+
+        case (ast.expr_cont) {
+            ret expr;
+        }
+
         case (ast.expr_ret(?expr_opt)) {
             alt (expr_opt) {
                 case (none[@ast.expr]) {

Diff for: src/test/run-pass/break.rs

@@ -0,0 +1,40 @@
+// xfail-boot
+
+fn main() {
+  auto i = 0;
+  while (i < 20) {
+    i += 1;
+    if (i == 10) { break; }
+  }
+  check(i == 10);
+
+  do {
+    i += 1;
+    if (i == 20) { break; }
+  } while (i < 30);
+  check(i == 20);
+
+  for (int x in vec(1, 2, 3, 4, 5, 6)) {
+    if (x == 3) { break; }
+    check(x <= 3);
+  }
+
+  i = 0;
+  while (i < 10) {
+    i += 1;
+    if (i % 2 == 0) { cont; }
+    check(i % 2 != 0);
+  }
+
+  i = 0;
+  do {
+    i += 1;
+    if (i % 2 == 0) { cont; }
+    check(i % 2 != 0);
+  } while (i < 10);
+
+  for (int x in vec(1, 2, 3, 4, 5, 6)) {
+    if (x % 2 == 0) { cont; }
+    check(x % 2 != 0);
+  }
+}