sometimes files do not exist for positions

Author: bishabosha

compiler/src/dotty/tools/dotc/reporting/MessageRendering.scala

@@ -149,10 +149,13 @@ trait MessageRendering {
     if (posString.nonEmpty) sb.append(posString).append(EOL)
     if (pos.exists) {
       val pos1 = pos.nonInlined
-      val (srcBefore, srcAfter, offset) = sourceLines(pos1, diagnosticLevel)
-      val marker = columnMarker(pos1, offset, diagnosticLevel)
-      val err = errorMsg(pos1, msg.message, offset)
-      sb.append((srcBefore ::: marker :: err :: outer(pos, " " * (offset - 1)) ::: srcAfter).mkString(EOL))
+      if (pos1.exists && pos1.source.file.exists) {
+        val (srcBefore, srcAfter, offset) = sourceLines(pos1, diagnosticLevel)
+        val marker = columnMarker(pos1, offset, diagnosticLevel)
+        val err = errorMsg(pos1, msg.message, offset)
+        sb.append((srcBefore ::: marker :: err :: outer(pos, " " * (offset - 1)) ::: srcAfter).mkString(EOL))
+      }
+      else sb.append(msg.message)
     }
     else sb.append(msg.message)
     sb.toString

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

@@ -196,7 +196,7 @@ class SourceFile(val file: AbstractFile, computeContent: => Array[Char]) extends
     var idx = startOfLine(offset)
     var col = 0
     while (idx != offset) {
-      col += (if (idx < length && content()(idx) == '\t') (tabInc - col) % tabInc else 1)
+      col += (if (idx < content().length && content()(idx) == '\t') (tabInc - col) % tabInc else 1)
       idx += 1
     }
     col
@@ -285,4 +285,3 @@ object SourceFile {
   override def exists: Boolean = false
   override def atSpan(span: Span): SourcePosition = NoSourcePosition
 }
-