Fix emacs indentation of multi-line match patterns

Aligns to the same column if the previous line ends in a single '|' (but
not a '||').

Author: MicahChalmer

src/etc/emacs/rust-mode-tests.el

@@ -425,6 +425,44 @@ fn foo()
 "
    ))
 
+(ert-deftest indent-match ()
+  (test-indent
+   "
+fn foo() {
+    match blah {
+        Pattern => stuff(),
+        _ => whatever
+    }
+}
+"
+   ))
+
+(ert-deftest indent-match-multiline-pattern ()
+  (test-indent
+   "
+fn foo() {
+    match blah {
+        Pattern |
+        Pattern2 => {
+            hello()
+        },
+        _ => whatever
+    }
+}
+"
+   ))
+
+;; Make sure that in effort to cover match patterns we don't mistreat || or expressions
+(ert-deftest indent-nonmatch-or-expression ()
+  (test-indent
+   "
+fn foo() {
+    let x = foo() ||
+        bar();
+}
+"
+   ))
+
 (setq rust-test-motion-string
       "
 fn fn1(arg: int) -> bool {

src/etc/emacs/rust-mode.el

@@ -85,7 +85,7 @@
               ;;  - { means indent to either nesting-level * rust-indent-offset,
               ;;    or one further indent from that if either current line
               ;;    begins with 'else', or previous line didn't end in
-              ;;    semi, comma or brace (other than whitespace and line
+              ;;    semi, comma, brace or single pipe (other than whitespace and line
               ;;    comments) , and wasn't an attribute.  But if we have
               ;;    something after the open brace and ending with a comma,
               ;;    treat it as fields and align them.  PHEW.
@@ -105,8 +105,7 @@
                            (beginning-of-line)
                            (rust-rewind-irrelevant)
                            (end-of-line)
-                           (if (looking-back
-                                "[[,;{}(][[:space:]]*\\(?://.*\\)?")
+                           (if (looking-back "\\(?:[(,:;?[{}]\\|[^|]|\\)[[:space:]]*\\(?://.*\\)?")
                                (* rust-indent-offset level)
                              (back-to-indentation)
                              (if (looking-at "#")