From 59556fd4510d7b22b0e3c3dbeca648fa63b6d6c6 Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Sat, 11 Jun 2022 16:14:03 +0200
Subject: [PATCH] Defensive code to make sure there's no infinite loop in
 `skip`.

---
 compiler/src/dotty/tools/dotc/parsing/Scanners.scala | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/compiler/src/dotty/tools/dotc/parsing/Scanners.scala b/compiler/src/dotty/tools/dotc/parsing/Scanners.scala
index 93ce23cbc103..f987ecd595fe 100644
--- a/compiler/src/dotty/tools/dotc/parsing/Scanners.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/Scanners.scala
@@ -313,8 +313,13 @@ object Scanners {
           // when skipping and therefore might erroneously end up syncing on a nested OUTDENT.
       if debugTokenStream then
         println(s"\nSTART SKIP AT ${sourcePos().line + 1}, $this in $currentRegion")
-      while !atStop do
+      var noProgress = 0
+        // Defensive measure to ensure we always get out of the following while loop
+        // even if source file is weirly formatted (i.e. we never reach EOF
+      while !atStop && noProgress < 3 do
+        val prevOffset = offset
         nextToken()
+        if offset == prevOffset then noProgress += 1 else noProgress = 0
       if debugTokenStream then
         println(s"\nSTOP SKIP AT ${sourcePos().line + 1}, $this in $currentRegion")
       if token == OUTDENT then dropUntil(_.isInstanceOf[Indented])