rustc: If all if branches are _|_, then the entire if is _|_

Author: brson

src/comp/middle/typeck.rs

@@ -2144,10 +2144,8 @@ fn check_expr(&@stmt_ctxt scx, &@ast::expr expr) {
                     if (!ty::type_is_bot(scx.fcx.ccx.tcx, elsopt_t)) {
                         Pushdown::pushdown_expr(scx, thn_t, els);
                         if_t = elsopt_t;
-                    } else if (!ty::type_is_bot(scx.fcx.ccx.tcx, thn_t)) {
-                        if_t = thn_t;
                     } else {
-                        if_t = ty::mk_nil(scx.fcx.ccx.tcx);
+                        if_t = thn_t;
                     }
                 }
                 case (none[@ast::expr]) {

src/test/run-pass/expr-if-fail-all.rs

@@ -0,0 +1,16 @@
+// xfail-stage0
+
+// When all branches of an if expression result in fail, the entire if
+// expression results in fail.
+
+fn main() {
+  auto x = if (true) {
+    10
+  } else {
+    if (true) {
+      fail
+    } else {
+      fail
+    }
+  };
+}