Avoid crasher when first token of a program is in error

src/dotty/tools/backend/jvm/DottyBackendInterface.scala

@@ -480,7 +480,7 @@ class DottyBackendInterface()(implicit ctx: Context) extends BackendInterface{
 
   implicit def positionHelper(a: Position): PositionHelper = new PositionHelper {
     def isDefined: Boolean = a.exists
-    def line: Int = sourcePos(a).line
+    def line: Int = sourcePos(a).line + 1
     def finalPosition: Position = a
   }
 

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()

src/dotty/tools/dotc/reporting/ConsoleReporter.scala

@@ -25,7 +25,7 @@ class ConsoleReporter(
     printMessage(pos.lineContents.stripLineEnd)
 
   def printColumnMarker(pos: SourcePosition) =
-    if (pos.exists) { printMessage(" " * (pos.column - 1) + "^") }
+    if (pos.exists) { printMessage(" " * pos.column + "^") }
 
   /** Prints the message. */
   def printMessage(msg: String): Unit = { writer.print(msg + "\n"); writer.flush() }

src/dotty/tools/dotc/util/SourceFile.scala

@@ -72,15 +72,15 @@ case class SourceFile(file: AbstractFile, content: Array[Char]) {
   def positionInUltimateSource(position: SourcePosition): SourcePosition =
     SourcePosition(underlying, position.pos shift start)
 
-  def isLineBreak(idx: Int) =
+  private def isLineBreak(idx: Int) =
     if (idx >= length) false else {
       val ch = content(idx)
       // don't identify the CR in CR LF as a line break, since LF will do.
       if (ch == CR) (idx + 1 == length) || (content(idx + 1) != LF)
       else isLineBreakChar(ch)
     }
 
-  def calculateLineIndices(cs: Array[Char]) = {
+  private def calculateLineIndices(cs: Array[Char]) = {
     val buf = new ArrayBuffer[Int]
     buf += 0
     for (i <- 0 until cs.length) if (isLineBreak(i)) buf += i + 1
@@ -103,22 +103,29 @@ case class SourceFile(file: AbstractFile, content: Array[Char]) {
     lastLine
   }
 
-  def startOfLine(offset: Int): Int = lineToOffset(offsetToLine(offset))
+  /** The index of the first character of the line containing position `offset` */
+  def startOfLine(offset: Int): Int = {
+    require(offset >= 0)
+    lineToOffset(offsetToLine(offset))
+  }
 
+  /** The start index of the line following the one containing position `offset` */
   def nextLine(offset: Int): Int =
     lineToOffset(offsetToLine(offset) + 1 min lineIndices.length - 1)
 
+  /** The contents of the line containing position `offset` */
   def lineContents(offset: Int): String =
     content.slice(startOfLine(offset), nextLine(offset)).mkString
 
+  /** The column corresponding to `offset`, starting at 0 */
   def column(offset: Int): Int = {
     var idx = startOfLine(offset)
     var col = 0
     while (idx != offset) {
-      col += (if (content(idx) == '\t') tabInc - col % tabInc else 1)
+      col += (if (content(idx) == '\t') (tabInc - col) % tabInc else 1)
       idx += 1
     }
-    col + 1
+    col
   }
 
   override def toString = file.toString

src/dotty/tools/dotc/util/SourcePosition.scala

@@ -10,7 +10,11 @@ case class SourcePosition(source: SourceFile, pos: Position) {
   def exists = pos.exists
 
   def lineContents: String = source.lineContents(point)
+
+  /** The line of the position, starting at 0 */
   def line: Int = source.offsetToLine(point)
+
+  /** The column of the position, starting at 0 */
   def column: Int = source.column(point)
 
   override def toString =

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)
 

tests/neg/firstError.scala

@@ -0,0 +1,4 @@
+.
+
+\u890u3084eu
+

tests/run/origins.check

@@ -1,6 +1,6 @@
 
 >> Origins tag 'boop' logged 65 calls from 3 distinguished sources.
 
-     50   Test$.$anonfun$f3$1(origins.scala:21)
-     10   Test$.$anonfun$f2$1(origins.scala:20)
-      5   Test$.$anonfun$f1$1(origins.scala:19)
+     50   Test$.$anonfun$f3$1(origins.scala:22)
+     10   Test$.$anonfun$f2$1(origins.scala:21)
+      5   Test$.$anonfun$f1$1(origins.scala:20)