From 774c6d01984b608047afedb5d8c579c00d69823f Mon Sep 17 00:00:00 2001
From: Tim Chevalier <chevalier@alum.wellesley.edu>
Date: Fri, 10 Jun 2011 14:34:01 -0700
Subject: [PATCH] Friendlier error message for break outside a loop

The typechecker should really check for this, but at least now
there's an error message rather than an inexhaustive match failure
in trans.
---
 src/comp/middle/trans.rs                    | 19 ++++++++++++-------
 src/test/compile-fail/break-outside-loop.rs |  7 +++++++
 2 files changed, 19 insertions(+), 7 deletions(-)
 create mode 100644 src/test/compile-fail/break-outside-loop.rs

diff --git a/src/comp/middle/trans.rs b/src/comp/middle/trans.rs
index 2c0965ead2fc..d1b5d39516d0 100644
--- a/src/comp/middle/trans.rs
+++ b/src/comp/middle/trans.rs
@@ -5691,11 +5691,11 @@ fn trans_expr_out(&@block_ctxt cx, &@ast::expr e, out_method output)
         }
 
         case (ast::expr_break(?a)) {
-            ret trans_break(cx);
+            ret trans_break(e.span, cx);
         }
 
         case (ast::expr_cont(?a)) {
-            ret trans_cont(cx);
+            ret trans_cont(e.span, cx);
         }
 
         case (ast::expr_ret(?e, _)) {
@@ -5972,7 +5972,7 @@ 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 {
+fn trans_break_cont(&span sp, &@block_ctxt cx, bool to_end) -> result {
     auto bcx = cx;
     // Locate closest loop block, outputting cleanup as we go.
     auto cleanup_cx = cx;
@@ -5998,6 +5998,11 @@ fn trans_break_cont(&@block_ctxt cx, bool to_end) -> result {
             case (_) {
                 alt ({cleanup_cx.parent}) {
                     case (parent_some(?cx)) { cleanup_cx = cx; }
+                    case (parent_none) {
+                        cx.fcx.lcx.ccx.sess.span_err(sp,
+                         (if (to_end) { "Break" } else { "Cont" })
+                          + " outside a loop");
+                    }
                 }
             }
         }
@@ -6007,12 +6012,12 @@ fn trans_break_cont(&@block_ctxt cx, bool to_end) -> result {
     cx.fcx.lcx.ccx.sess.bug("in trans::trans_break_cont()");
 }
 
-fn trans_break(&@block_ctxt cx) -> result {
-    ret trans_break_cont(cx, true);
+fn trans_break(&span sp, &@block_ctxt cx) -> result {
+    ret trans_break_cont(sp, cx, true);
 }
 
-fn trans_cont(&@block_ctxt cx) -> result {
-    ret trans_break_cont(cx, false);
+fn trans_cont(&span sp, &@block_ctxt cx) -> result {
+    ret trans_break_cont(sp, cx, false);
 }
 
 
diff --git a/src/test/compile-fail/break-outside-loop.rs b/src/test/compile-fail/break-outside-loop.rs
new file mode 100644
index 000000000000..9c5d8c5e7ed3
--- /dev/null
+++ b/src/test/compile-fail/break-outside-loop.rs
@@ -0,0 +1,7 @@
+// error-pattern:Break outside a loop
+fn main() {
+  auto pth = break;
+
+  let rec(str t) res = rec(t=pth);
+
+}
\ No newline at end of file