Add rust-indent-return-type-to-arguments variable

This preserves as default (t), the current indentation behavior of `->
ReturnType` when found on its own line: indenting as per the arguments
of the above function.  When disabled (nil) by the user, however, this
will now just indent such a line one level from base-line (e.g. no
special treatment).

Includes a basic test.

1 files changed, 11 insertions, 0 deletions

diff --git a/rust-mode-tests.el b/rust-mode-tests.el
index 9d87960..a5fea28 100644
--- a/rust-mode-tests.el
+++ b/rust-mode-tests.el
@@ -450,6 +450,17 @@ fn foo4(a:i32,
 }
 "))
 
+(ert-deftest indent-return-type-non-visual ()
+  (let ((rust-indent-return-type-to-arguments nil))
+(test-indent
+   "
+fn imagine_long_enough_to_wrap_at_arrow(a:i32, b:char)
+    -> i32
+{
+    let body;
+}
+")))
+
 (ert-deftest indent-body-after-where ()
   (let ((rust-indent-where-clause t))
     (test-indent