From 8edd90dd26e3acf652ea4a24e288d7f9a57a5cb4 Mon Sep 17 00:00:00 2001
From: Rico Tzschichholz <ricotz@ubuntu.com>
Date: Tue, 16 Jun 2020 14:55:04 +0200
Subject: [PATCH] parser: Avoid mitigation for missing token if it follows DOT
 or DOUBLE_COLON

Rolling back to a DOT/DOUBLE_COLON token will retrigger the attempt to parse
an incomplete member access.

Regression of 4368a4fa667148378dcdbd251a4ae4e00c9a8e5a

Fixes https://gitlab.gnome.org/GNOME/vala/issues/987
---
 vala/valaparser.vala | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/vala/valaparser.vala b/vala/valaparser.vala
index 191bc75d5..3adc6e71a 100644
--- a/vala/valaparser.vala
+++ b/vala/valaparser.vala
@@ -104,10 +104,25 @@ public class Vala.Parser : CodeVisitor {
 		assert (size <= BUFFER_SIZE);
 	}
 
+	inline void safe_prev () {
+		switch (previous ()) {
+		case TokenType.DOT:
+		case TokenType.DOUBLE_COLON:
+			break;
+		default:
+			prev ();
+			break;
+		}
+	}
+
 	inline TokenType current () {
 		return tokens[index].type;
 	}
 
+	inline TokenType previous () {
+		return tokens[(index - 1 + BUFFER_SIZE) % BUFFER_SIZE].type;
+	}
+
 	inline bool accept (TokenType type) {
 		if (current () == type) {
 			next ();
@@ -129,13 +144,13 @@ public class Vala.Parser : CodeVisitor {
 
 		switch (type) {
 		case TokenType.CLOSE_BRACE:
-			prev ();
+			safe_prev ();
 			report_parse_error (new ParseError.SYNTAX ("following block delimiter %s missing", type.to_string ()));
 			return true;
 		case TokenType.CLOSE_BRACKET:
 		case TokenType.CLOSE_PARENS:
 		case TokenType.SEMICOLON:
-			prev ();
+			safe_prev ();
 			report_parse_error (new ParseError.SYNTAX ("following expression/statement delimiter %s missing", type.to_string ()));
 			return true;
 		default:
@@ -1686,9 +1701,7 @@ public class Vala.Parser : CodeVisitor {
 		try {
 			skip_type ();
 		} catch (ParseError e) {
-			prev ();
-			var token = current ();
-			next ();
+			var token = previous ();
 			if (token == TokenType.DOT || token == TokenType.DOUBLE_COLON) {
 				rollback (begin);
 				return true;
-- 
2.47.2