From d00572d159a3a15664afbf09d1ff914df4d2c512 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Thu, 25 Jun 2015 12:01:32 +0200
Subject: Avoid crasher when first token of a program is in error

This used to give a crash in SourcePositiom, promoted by feeding
its calculations with a negative offset.
---
 src/dotty/tools/dotc/parsing/Parsers.scala | 2 +-
 src/dotty/tools/dotc/util/SourceFile.scala | 5 ++++-
 test/dotc/tests.scala                      | 1 +
 tests/neg/firstError.scala                 | 4 ++++
 4 files changed, 10 insertions(+), 2 deletions(-)
 create mode 100644 tests/neg/firstError.scala

diff --git a/src/dotty/tools/dotc/parsing/Parsers.scala b/src/dotty/tools/dotc/parsing/Parsers.scala
index b79077245..2a42a7fa9 100644
--- a/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -192,7 +192,7 @@ object Parsers {
           case _ =>
             if (mustStartStat &&
                 in.isAfterLineEnd() &&
-                isLeqIndented(in.offset, lastStatOffset))
+                isLeqIndented(in.offset, lastStatOffset max 0))
               return
         }
         in.nextToken()
diff --git a/src/dotty/tools/dotc/util/SourceFile.scala b/src/dotty/tools/dotc/util/SourceFile.scala
index 45119a881..6e2ac7d79 100644
--- a/src/dotty/tools/dotc/util/SourceFile.scala
+++ b/src/dotty/tools/dotc/util/SourceFile.scala
@@ -103,7 +103,10 @@ case class SourceFile(file: AbstractFile, content: Array[Char]) {
     lastLine
   }
 
-  def startOfLine(offset: Int): Int = lineToOffset(offsetToLine(offset))
+  def startOfLine(offset: Int): Int = {
+    require(offset >= 0)
+    lineToOffset(offsetToLine(offset))
+  }
 
   def nextLine(offset: Int): Int =
     lineToOffset(offsetToLine(offset) + 1 min lineIndices.length - 1)
diff --git a/test/dotc/tests.scala b/test/dotc/tests.scala
index 1aa35e3ee..520abc222 100644
--- a/test/dotc/tests.scala
+++ b/test/dotc/tests.scala
@@ -140,6 +140,7 @@ class tests extends CompilerTest {
   @Test def neg_shadowedImplicits = compileFile(negDir, "arrayclone-new", xerrors = 2)
   @Test def neg_traitParamsTyper = compileFile(negDir, "traitParamsTyper", xerrors = 5)
   @Test def neg_traitParamsMixin = compileFile(negDir, "traitParamsMixin", xerrors = 2)
+  @Test def neg_firstError = compileFile(negDir, "firstError", xerrors = 3)
 
   @Test def run_all = runFiles(runDir)
 
diff --git a/tests/neg/firstError.scala b/tests/neg/firstError.scala
new file mode 100644
index 000000000..317adcced
--- /dev/null
+++ b/tests/neg/firstError.scala
@@ -0,0 +1,4 @@
+.
+
+\u890u3084eu
+
-- 
cgit v1.2.3