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

rustic-interaction.el

@@ -175,8 +175,10 @@
                        (back-to-indentation)
                        (current-column))))))
 
-              ;; A function return type is indented to the corresponding function arguments
-              ((looking-at "->")
+               ;; A function return type is indented to the corresponding
+	           ;; function arguments, if -to-arguments is selected.
+              ((and rust-indent-return-type-to-arguments
+		            (looking-at "->"))
                (save-excursion
                  (backward-list)
                  (or (rustic-align-to-expr-after-brace)

rustic.el

@@ -110,6 +110,12 @@ function or trait.  When nil, where will be aligned with fn or trait."
   :type 'boolean
   :group 'rustic)
 
+(defcustom rust-indent-return-type-to-arguments t
+  "Indent a line starting with the `->' (RArrow) following a function, aligning
+to the function arguments.  When nil, `->' will be indented one level."
+  :type 'boolean
+  :group 'rust-mode
+  :safe #'booleanp)
 
 ;;;;;;;;;;;;;;;;;;
 ;; Faces

test/rustic-rust-mode-test.el

@@ -1587,4 +1587,14 @@ extern \"rustic-intrinsic\" fn five() {
     (test-electric-pair-insert "fn foo() -> Box" 16 ?< ?>))
   )
 
-;;; rustic-mode-tests.el ends here
+(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;
+}
+")))
+