---

yaml
---
r: 29853
b: refs/heads/incoming
c: c0140f5
h: refs/heads/master
i:
  29851: f3064e7
v: v3

Author: catamorphism

[refs]

@@ -6,7 +6,7 @@ refs/heads/try: d324a424d8f84b1eb049b12cf34182bda91b0024
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/heads/ndm: f3868061cd7988080c30d6d5bf352a5a5fe2460b
 refs/heads/try2: d0c6ce338884ee21843f4b40bf6bf18d222ce5df
-refs/heads/incoming: a83414b6e8879b2485374469f7f5fe60f22ae936
+refs/heads/incoming: c0140f5c344a206b4147d03d306bd6c83468d30b
 refs/heads/dist-snap: 2f32a1581f522e524009138b33b1c7049ced668d
 refs/tags/release-0.2: c870d2dffb391e14efb05aa27898f1f6333a9596
 refs/tags/release-0.3: b5f0d0f648d9a6153664837026ba1be43d3e2503

branches/incoming/src/rustc/middle/check_alt.rs

@@ -4,6 +4,7 @@ import const_eval::{eval_const_expr, const_val, const_int,
                     compare_const_vals};
 import syntax::codemap::span;
 import syntax::print::pprust::pat_to_str;
+import util::ppaux::ty_to_str;
 import pat_util::*;
 import syntax::visit;
 import driver::session::session;
@@ -29,10 +30,15 @@ fn check_expr(tcx: ty::ctxt, ex: @expr, &&s: (), v: visit::vt<()>) {
          // Check for empty enum, because is_useful only works on inhabited
          // types.
        let pat_ty = node_id_to_type(tcx, scrut.id);
-       if type_is_empty(tcx, pat_ty) && arms.is_empty() {
-               // Vacuously exhaustive
-               return;
+       if arms.is_empty() {
+           if !type_is_empty(tcx, pat_ty) {
+               // We know the type is inhabited, so this must be wrong
+               tcx.sess.span_err(ex.span, #fmt("non-exhaustive patterns: \
+                             type %s is non-empty", ty_to_str(tcx, pat_ty)));
            }
+           // If the type *is* empty, it's vacuously exhaustive
+           return;
+       }
        match ty::get(pat_ty).struct {
           ty_enum(did, _) => {
               if (*enum_variants(tcx, did)).is_empty() && arms.is_empty() {

branches/incoming/src/test/compile-fail/issue-3096-1.rs

@@ -0,0 +1,3 @@
+fn main() {
+    match () { } //~ ERROR non-exhaustive
+}

branches/incoming/src/test/compile-fail/issue-3096-2.rs

@@ -0,0 +1,6 @@
+enum bottom { } 
+
+fn main() {
+    let x = ptr::addr_of(()) as *bottom;
+    match x { } //~ ERROR non-exhaustive patterns
+}