make list_suffix/1 and list_prefix/1 handle erl_parse() cons sequences

1 files changed, 18 insertions, 8 deletions

diff --git a/lib/syntax_tools/src/erl_syntax.erl b/lib/syntax_tools/src/erl_syntax.erl
index beae6f4a01..76a6a6dc36 100644
--- a/lib/syntax_tools/src/erl_syntax.erl
+++ b/lib/syntax_tools/src/erl_syntax.erl
@@ -2061,12 +2061,18 @@ revert_nil(Node) ->
 
 list_prefix(Node) ->
     case unwrap(Node) of
-	{cons, _, Head, _} ->
-	    [Head];
+	{cons, _, Head, Tail} ->
+	    [Head | cons_prefix(Tail)];
 	Node1 ->
 	    (data(Node1))#list.prefix
     end.
 
+%% collects sequences of conses; cf. cons_suffix/1 below
+cons_prefix({cons, _, Head, Tail}) ->
+    [Head | cons_prefix(Tail)];
+cons_prefix(_) ->
+    [].
+
 
 %% =====================================================================
 %% @doc Returns the suffix subtree of a `list' node, if one
@@ -2090,18 +2096,22 @@ list_prefix(Node) ->
 list_suffix(Node) ->
     case unwrap(Node) of
 	{cons, _, _, Tail} ->
-	    %% If there could be comments/annotations on the tail node,
-	    %% we should not return `none' even if it has type `nil'.
-	    case Tail of
+	    case cons_suffix(Tail) of
 		{nil, _} ->
-		    none;    % no interesting information is lost
-		_ ->
-		    Tail
+		    none;
+		Tail1 ->
+		    Tail1
 	    end;
 	Node1 ->
 	    (data(Node1))#list.suffix
     end.
 
+%% skips sequences of conses; cf. cons_prefix/1 above
+cons_suffix({cons, _, _, Tail}) ->
+    cons_suffix(Tail);
+cons_suffix(Tail) ->
+    Tail.
+
 
 %% =====================================================================
 %% @doc "Optimising" list skeleton cons operation. Creates an abstract