Auto merge of #42265 - Zoxc:for-sugar, r=eddyb

Change for-loop desugar to not borrow the iterator during the loop

This is enables the use of suspend points inside for-loops in movable generators. This is illegal in the current desugaring as `iter` is borrowed across the body.

2 files changed, 18 insertions, 1 deletions

diff --git a/src/test/compile-fail/E0297.rs b/src/test/compile-fail/E0297.rs
index 5792ba06eb0..436e4c1f9d2 100644
--- a/src/test/compile-fail/E0297.rs
+++ b/src/test/compile-fail/E0297.rs
@@ -12,6 +12,6 @@ fn main() {
     let xs : Vec<Option<i32>> = vec![Some(1), None];
 
     for Some(x) in xs {}
-    //~^ ERROR E0297
+    //~^ ERROR E0005
     //~| NOTE pattern `None` not covered
 }
diff --git a/src/test/compile-fail/for-loop-has-unit-body.rs b/src/test/compile-fail/for-loop-has-unit-body.rs
new file mode 100644
index 00000000000..8c61fc602e0
--- /dev/null
+++ b/src/test/compile-fail/for-loop-has-unit-body.rs
@@ -0,0 +1,17 @@
+// Copyright 2017 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.
+
+fn main() {
+    for x in 0..3 {
+        x //~ ERROR mismatched types
+        //~| NOTE expected ()
+        //~| NOTE expected type `()`
+    }
+}