Auto merge of #36029 - KiChjang:issue-12033, r=arielb1

Fix lifetime rules for 'if' conditions

Fixes #12033.

Changes the temporary scope rules to make the condition of an if-then-else a terminating scope. This is a [breaking-change].

Author: bors

src/librustc/middle/region.rs

@@ -803,7 +803,8 @@ fn resolve_expr(visitor: &mut RegionResolutionVisitor, expr: &hir::Expr) {
                 terminating(r.id);
             }
 
-            hir::ExprIf(_, ref then, Some(ref otherwise)) => {
+            hir::ExprIf(ref expr, ref then, Some(ref otherwise)) => {
+                terminating(expr.id);
                 terminating(then.id);
                 terminating(otherwise.id);
             }

src/test/run-pass/issue-12033.rs

@@ -0,0 +1,16 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::cell::RefCell;
+
+fn main() {
+    let x = RefCell::new(0);
+    if *x.borrow() == 0 {} else {}
+}