Teach rustc to fail

src/comp/front/ast.rs

@@ -116,6 +116,7 @@ tag stmt_ {
     stmt_ret(option.t[@expr]);
     stmt_log(@expr);
     stmt_check_expr(@expr);
+    stmt_fail;
     stmt_expr(@expr);
 }
 

src/comp/front/parser.rs

@@ -1158,6 +1158,11 @@ impure fn parse_stmt(parser p) -> @ast.stmt {
             }
         }
 
+        case (token.FAIL) {
+            p.bump();
+            ret @spanned(lo, p.get_span(), ast.stmt_fail);
+        }
+
         case (token.RET) {
             p.bump();
             alt (p.peek()) {
@@ -1315,6 +1320,7 @@ fn stmt_ends_with_semi(@ast.stmt stmt) -> bool {
         case (ast.stmt_ret(_))                  { ret true; }
         case (ast.stmt_log(_))                  { ret true; }
         case (ast.stmt_check_expr(_))           { ret true; }
+        case (ast.stmt_fail)                    { ret true; }
         case (ast.stmt_expr(?e)) {
             alt (e.node) {
                 case (ast.expr_vec(_,_))        { ret true; }

src/comp/middle/fold.rs

@@ -615,6 +615,10 @@ fn fold_stmt[ENV](&ENV env, ast_fold[ENV] fld, &@stmt s) -> @stmt {
             ret fld.fold_stmt_check_expr(env_, s.span, ee);
         }
 
+        case (ast.stmt_fail) {
+            ret s;
+        }
+
         case (ast.stmt_expr(?e)) {
             auto ee = fold_expr(env_, fld, e);
             ret fld.fold_stmt_expr(env_, s.span, ee);

src/comp/middle/trans.rs

@@ -2251,11 +2251,7 @@ fn trans_index(@block_ctxt cx, &ast.span sp, @ast.expr base,
     ix.bcx.build.CondBr(bounds_check, next_cx.llbb, fail_cx.llbb);
 
     // fail: bad bounds check.
-    auto V_expr_str = p2i(C_cstr(cx.fcx.ccx, "out-of-bounds access"));
-    auto V_filename = p2i(C_cstr(cx.fcx.ccx, sp.filename));
-    auto V_line = sp.lo.line as int;
-    auto args = vec(V_expr_str, V_filename, C_int(V_line));
-    auto fail_res = trans_upcall(fail_cx, "upcall_fail", args);
+    auto fail_res = trans_fail(fail_cx, sp, "bounds check");
     fail_res.bcx.build.Br(next_cx.llbb);
 
     auto body = next_cx.build.GEP(v, vec(C_int(0), C_int(abi.vec_elt_data)));
@@ -2904,13 +2900,9 @@ fn trans_check_expr(@block_ctxt cx, @ast.expr e) -> result {
     auto cond_res = trans_expr(cx, e);
 
     // FIXME: need pretty-printer.
-    auto V_expr_str = p2i(C_cstr(cx.fcx.ccx, "<expr>"));
-    auto V_filename = p2i(C_cstr(cx.fcx.ccx, e.span.filename));
-    auto V_line = e.span.lo.line as int;
-    auto args = vec(V_expr_str, V_filename, C_int(V_line));
-
+    auto expr_str = "<expr>";
     auto fail_cx = new_sub_block_ctxt(cx, "fail");
-    auto fail_res = trans_upcall(fail_cx, "upcall_fail", args);
+    auto fail_res = trans_fail(fail_cx, e.span, expr_str);
 
     auto next_cx = new_sub_block_ctxt(cx, "next");
     fail_res.bcx.build.Br(next_cx.llbb);
@@ -2920,6 +2912,15 @@ fn trans_check_expr(@block_ctxt cx, @ast.expr e) -> result {
     ret res(next_cx, C_nil());
 }
 
+fn trans_fail(@block_ctxt cx, common.span sp, str fail_str) -> result {
+    auto V_fail_str = p2i(C_cstr(cx.fcx.ccx, fail_str));
+    auto V_filename = p2i(C_cstr(cx.fcx.ccx, sp.filename));
+    auto V_line = sp.lo.line as int;
+    auto args = vec(V_fail_str, V_filename, C_int(V_line));
+
+    ret trans_upcall(cx, "upcall_fail", args);
+}
+
 fn trans_ret(@block_ctxt cx, &option.t[@ast.expr] e) -> result {
     auto bcx = cx;
     auto val = C_nil();
@@ -3035,6 +3036,10 @@ fn trans_stmt(@block_ctxt cx, &ast.stmt s) -> result {
             bcx = trans_check_expr(cx, a).bcx;
         }
 
+        case (ast.stmt_fail) {
+            bcx = trans_fail(cx, s.span, "explicit failure").bcx;
+        }
+
         case (ast.stmt_ret(?e)) {
             bcx = trans_ret(cx, e).bcx;
         }

src/comp/middle/typeck.rs

@@ -1682,6 +1682,10 @@ fn check_stmt(&@fn_ctxt fcx, &@ast.stmt stmt) -> @ast.stmt {
                                         ast.stmt_check_expr(expr_t));
         }
 
+        case (ast.stmt_fail) {
+            ret stmt;
+        }
+
         case (ast.stmt_expr(?expr)) {
             auto expr_t = check_expr(fcx, expr);
             ret @fold.respan[ast.stmt_](stmt.span, ast.stmt_expr(expr_t));