Minor fixes to emacs erlang-mode

Fix "Unbalanced parentheses" error when indenting particular map
constructs. Add new test cases for this fix.

To prevent infinite looping when the programmer mistakenly enters
incorrect syntax, detect cases where erlang-partial-parse fails to
advance when called within a loop, and raise an "Illegal syntax"
error.

3 files changed, 38 insertions, 9 deletions

diff --git a/lib/tools/emacs/erlang.el b/lib/tools/emacs/erlang.el
index 0c003bab39..3610356355 100644
--- a/lib/tools/emacs/erlang.el
+++ b/lib/tools/emacs/erlang.el
@@ -2444,7 +2444,10 @@ This is automagically called by the user level function `indent-region'."
       ;; Parse the Erlang code from the beginning of the clause to
       ;; the beginning of the region.
       (while (< (point) indent-point)
-	(setq state (erlang-partial-parse (point) indent-point state)))
+        (let ((pt (point)))
+          (setq state (erlang-partial-parse pt indent-point state))
+          (if (= pt (point))
+              (error "Illegal syntax"))))
       ;; Indent every line in the region
       (while continue
 	(goto-char indent-point)
@@ -2480,8 +2483,11 @@ This is automagically called by the user level function `indent-region'."
 	(if (>= from-end (- (point-max) indent-point))
 	    (setq continue nil)
 	  (while (< (point) indent-point)
-	    (setq state (erlang-partial-parse
-			 (point) indent-point state))))))))
+            (let ((pt (point)))
+              (setq state (erlang-partial-parse
+                           pt indent-point state))
+              (if (= pt (point))
+                  (error "Illegal syntax")))))))))
 
 
 (defun erlang-indent-current-buffer ()
@@ -2528,7 +2534,10 @@ Return nil if line starts inside string, t if in a comment."
 	  (goto-char parse-start)
 	(erlang-beginning-of-clause))
       (while (< (point) indent-point)
-	(setq state (erlang-partial-parse (point) indent-point state)))
+        (let ((pt (point)))
+          (setq state (erlang-partial-parse pt indent-point state))
+          (if (= pt (point))
+              (error "Illegal syntax"))))
       (erlang-calculate-stack-indent indent-point state))))
 
 (defun erlang-show-syntactic-information ()
@@ -2698,12 +2707,13 @@ Value is list (stack token-start token-type in-what)."
 	(erlang-push (list '|| token (current-column)) stack)
 	(forward-char 2))
 
-       ;; Bit-syntax open paren
-       ((looking-at "<<")
+       ;; Bit-syntax open. Note that map syntax allows "<<" to follow ":="
+       ;; or "=>" without intervening whitespace, so handle that case here
+       ((looking-at "\\(:=\\|=>\\)?<<")
 	(erlang-push (list '<< token (current-column)) stack)
-	(forward-char 2))
+	(forward-char (- (match-end 0) (match-beginning 0))))
        
-       ;; Bbit-syntax close paren
+       ;; Bit-syntax close
        ((looking-at ">>")
 	(while (memq (car (car stack)) '(|| ->))
 	  (erlang-pop stack))
@@ -4188,7 +4198,10 @@ This function is designed to be a member of a criteria list."
 	    ;; Do not return `stop' when inside a list comprehension
 	    ;; construction.  (The point must be after `||').
 	    (while (< (point) orig-point)
-	      (setq state (erlang-partial-parse (point) orig-point state)))
+              (let ((pt (point)))
+                (setq state (erlang-partial-parse pt orig-point state))
+                (if (= pt (point))
+                    (error "Illegal syntax"))))
 	    (if (and (car state) (eq (car (car (car state))) '||))
 		nil
 	      'stop)))
diff --git a/lib/tools/emacs/test.erl.indented b/lib/tools/emacs/test.erl.indented
index 1c1086ca58..abb05fd59b 100644
--- a/lib/tools/emacs/test.erl.indented
+++ b/lib/tools/emacs/test.erl.indented
@@ -32,6 +32,14 @@
 -module(test).
 -compile(export_all).
 
+%% Used to cause an "Unbalanced parentheses" error.
+foo(M) ->
+    M#{a :=<<"a">>
+      ,b:=1}.
+foo() ->
+    #{a =><<"a">>
+     ,b=>1}.
+
 %% Module attributes should be highlighted
 
 -export([t/1]).
diff --git a/lib/tools/emacs/test.erl.orig b/lib/tools/emacs/test.erl.orig
index a9d09000d2..3d8f29fe18 100644
--- a/lib/tools/emacs/test.erl.orig
+++ b/lib/tools/emacs/test.erl.orig
@@ -32,6 +32,14 @@
 -module(test).
 -compile(export_all).
 
+%% Used to cause an "Unbalanced parentheses" error.
+foo(M) ->
+M#{a :=<<"a">>
+,b:=1}.
+foo() ->
+#{a =><<"a">>
+,b=>1}.
+
 %% Module attributes should be highlighted
 
 -export([t/1]).